Ohly, Heather, White, M, P, Wheeler, B, W, Bethel, A, Ukoumunne, O, C, Nikolaou, V and Garside, R

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1 Article Attetio Restoratio Theory: A Systematic Review of the Attetio Restoratio Potetial of Exposure to Natural Eviromets Ohly, Heather, White, M, P, Wheeler, B, W, Bethel, A, Ukoumue, O, C, Nikolaou, V ad Garside, R Available at Ohly, Heather ORCID: , White, M, P, Wheeler, B, W, Bethel, A, Ukoumue, O, C, Nikolaou, V ad Garside, R (2016) Attetio Restoratio Theory: A Systematic Review of the Attetio Restoratio Potetial of Exposure to Natural Eviromets. Joural of Toxicology ad Evirometal Health, Part B. ISSN It is advisable to refer to the publisher s versio if you ited to cite from the work. For more iformatio about UCLa s research i this area go to ad search for <ame of research Group>. For iformatio about Research geerally at UCLa please go to All outputs i CLoK are protected by Itellectual Property Rights law, icludig Copyright law. Copyright, IPR ad Moral Rights for the works o this site are retaied by the idividual authors ad/or other copyright owers. Terms ad coditios for use of this material are defied i the CLoK Cetral Lacashire olie Kowledge

2 Joural of Toxicology ad Evirometal Health, Part B Critical Reviews ISSN: (Prit) (Olie) Joural homepage: Attetio Restoratio Theory: A Systematic Review of the Attetio Restoratio Potetial of Exposure to Natural Eviromets Heather Ohly, Mathew P. White, Beedict W. Wheeler, Aliso Bethel, Obioha C. Ukoumue, Vasilis Nikolaou & Ruth Garside To cite this article: Heather Ohly, Mathew P. White, Beedict W. Wheeler, Aliso Bethel, Obioha C. Ukoumue, Vasilis Nikolaou & Ruth Garside (2016): Attetio Restoratio Theory: A Systematic Review of the Attetio Restoratio Potetial of Exposure to Natural Eviromets, Joural of Toxicology ad Evirometal Health, Part B, DOI: / To lik to this article: Published with licese by Taylor & Fracis Group, LLC 2016 Heather Ohly, Mathew P. White, Beedict W. Wheeler, Aliso Bethel, Obioha C. Ukoumue, Vasilis Nikolaou, ad Ruth Garside Published olie: 26 Sep Submit your article to this joural Article views: 367 View related articles View Crossmark data Full Terms & Coditios of access ad use ca be foud at Dowload by: [Uiversity of Cetral Lacashire] Date: 19 October 2016, At: 02:01

3 JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH, PART B Attetio Restoratio Theory: A Systematic Review of the Attetio Restoratio Potetial of Exposure to Natural Eviromets Heather Ohly a, Mathew P. White a, Beedict W. Wheeler a, Aliso Bethel b, Obioha C. Ukoumue b, Vasilis Nikolaou b a, ad Ruth Garside a Europea Cetre for Eviromet ad Huma Health, Uiversity of Exeter Medical School, Truro Campus, ad Kowledge Spa, Royal Corwall Hospital, Truro, Corwall, Uited Kigdom; b NIHR CLAHRC South West Peisula, Uiversity of Exeter Medical School, South Cloisters, St Luke s Campus, Exeter, Devo, Uited Kigdom ABSTRACT Attetio Restoratio Theory (ART) suggests the ability to cocetrate may be restored by exposure to atural eviromets. Although widely cited, it is uclear as to the quatity of empirical evidece that supports this. A systematic review regardig the impact of exposure to atural eviromets o attetio was coducted. Seve electroic databases were searched. Studies were icluded if (1) they were atural experimets, radomized ivestigatios, or recorded before ad after measuremets; (2) compared atural ad oatural/other settigs; ad (3) used objective measures of attetio. Screeig of articles for iclusio, data extractio, ad quality appraisal were performed by oe reviewer ad checked by aother. Where possible, radom effects meta-aalysis was used to pool effect sizes. Thirty-oe studies were icluded. Meta-aalyses provided some support for ART, with sigificat positive effects of exposure to atural eviromets for three measures (Digit Spa Forward, Digit Spa Backward, ad Trail Makig Test B). The remaiig 10 meta-aalyses did ot show marked beeficial effects. Metaaalysis was limited by small umbers of ivestigatios, small samples, heterogeeity i reportig of study quality idicators, ad heterogeeity of outcomes. This review highlights the diversity of evidece aroud ART i terms of populatios, study desig, ad outcomes. There is ucertaity regardig which aspects of attetio may be affected by exposure to atural eviromets. There is icreasig practice ad policy iterest i the potetial for atural eviromets to provide positive huma health ad well-beig beefits. Attetio Restoratio Theory (ART) is commoly refereced to explai how this beefit might accrue; however, it is uclear how strog the empirical evidece is that exists for this proposed mechaism. I cogitive psychology, the ability to focus o a task that requires effort is kow as directed or volutary attetio (Kapla ad Kapla 1989). This ability is fiite ad may become fatigued. Attetio fatigue may occur whe there is a eed to focus o a specific stimulus or task with little or o itrisically motivatioal draw, while suppressig distractios that may be iheretly more iterestig, with a example beig fillig i a tax retur while your childre are playig i the yard (Kapla 1995; Kapla ad Berma 2010). Attetioal fatigue is importat, ot least because it is associated with poorer decisio makig ad lower levels of self-cotrol, which i tur have bee liked to a variety of healthrelated issues such as obesity via icreasigly uderstood eural ad behavioral pathways (Fa ad Ji 2013; Hare, Camerer, ad Ragel 2009; Vohs et al. 2008). More tha half the world s populatio lives i urba areas. From a psychological perspective, urba lifestyles impose icreasig demads o our cogitive resources (Kapla ad Berma 2010). Accordig to ART these ehaced demads o directed attetio may be liked to attetio fatigue (Kapla 1995; Kapla ad Kapla 1989). The atidote, the theory claims, is to take time out from attetio-demadig tasks associated with moder life, ad sped time i atural CONTACT Ruth Garside R.Garside@exeter.ac.uk Europea Cetre for Eviromet ad Huma Health, Uiversity of Exeter Medical School, Truro Campus, Kowledge Spa, Royal Corwall Hospital, Truro, Corwall, TR1 3HD, Uited Kigdom. Color versios of oe or more of the figures i the article ca be foud olie at Published with licese by Taylor & Fracis Group, LLC 2016 Heather Ohly, Mathew P. White, Beedict W. Wheeler, Aliso Bethel, Obioha C. Ukoumue, Vasilis Nikolaou, ad Ruth Garside This is a Ope Access article. No-commercial re-use, distributio, ad reproductio i ay medium, provided the origial work is properly attributed, cited, ad is ot altered, trasformed, or built upo i ay way, is permitted. The moral rights of the amed author(s) have bee asserted.

4 2 H. OHLY ET AL. eviromets that demad less of our cogitive resources ad eable us to recover our attetioal capacities. ART proposes that idividuals beefit from the chace to (1) be away from everyday stresses, (2) experiece expasive spaces ad cotexts ( extet ), (3) egage i activities that are compatible with our itrisic motivatios, ad (4) critically experiece stimuli that are softly fasciatig (Kapla 1995). This combiatio of factors ecourages ivolutary or idirect attetio ad eables our volutary or directed attetio capacities to recover ad restore (Kapla 1995; Staats 2012). Relaxig settigs (such as places of worship) ad activities (such as sleep) may provide restorative opportuities, but ART argues that ature may be particularly useful because it has a aesthetic advatage (Herzog et al. 2010; KaplaadBerma2010; Kapla ad Kapla 1989). It is suggested that sedig time i the atural world allows idividuals the opportuity for reflectio ad cosideratio of uresolved issues (Herzog et al. 1997; Kapla ad Berma 2010). The origial developmet of ART was largely descriptive, based o observatios of huma ature iteractios ad aalysis of qualitative data (Kapla ad Frey Talbot 1983). Kapla (1995) subsequetly liked ART more broadly to attetio theory, for istace, associatig directed attetio fatigue to problems i selectio ad problem solvig, ihibitio of competig stimuli, ad feeligs of irritability. More geeral psychological research provides behavioral ad eural evidece of a distictio betwee top-dow directed attetio ad bottom-up ivolutary attetio (Fa et al. 2005). Specifically, it has bee postulated that directed attetio is more liked to higher order metal fuctios because of a greater load o workig memory produced by, amog other thigs, the eed to suppress distractig stimuli or alterative attetioal cues. The simpler attetioal processes of alertig (becomig aware of somethig; Joides et al. 2008; Fa et al. 2002) ad orietig (takig actios to focus o a stimulus) should be less affected by the trials of moder livig because they demad relatively few cogitive resources. These processes are thus less likely to eed recovery i the same way as the executive fuctios of attetio, such as workig memory, which ot oly eeds to hold ad replay visual ad auditory stimuli, but may also have to maipulate them accordig to rules stored i short-term memory (Joides et al. 2008). This discussio is importat because it suggests that oly relatively demadig attetioal tasks should show improvemets followig exposure to ature. A example is the Backwards Digit Spa test, which requires participats to both remember ad maipulate (reverse) a series of umbers. I cotrast, tasks that require relatively few cogitive resources should be less demadig ad so less affected by exposure to ature. A example would be the Sustaied Attetio to Respose Task (SART), whichsimplyrequiresparticipatstoreacttothe presetatio of digits from 1 to 9 o a computer scree, for example, by pressig the space bar, except whe the umber 3 appears. The task thus ivolves ihibitig the most frequet respose (pressig a space bar) whe a rare evet occurs ad reflects the eed to sustai attetio rather tha drift ito overgeeralizig a behavioral respose. Taylor, Kuo, ad Sulliva (2002) explored whether childre livig i apartmets with greater surroudig gree space showed higher levels of self-disciplie, potetially due to fewer demads o attetio resources. Echoig this, Kapla ad Berma (2010) ad Baumeister, Vohs, ad Tice (2007) proposed that directed attetio fatigue may be liked to a loss i self-regulatio, such as the ability to resist temptatio, suggestig these two processes may share a commo resource. If true, relative depletio o tasks measurig self-regulatio ad the ability to ihibit actios, rather tha just directed attetio, might also be see followig exposure to urba versus atural eviromets. Kapla ad Berma (2010) preseted a umber of studies to support these claims. However, this review did ot aim to systematically collect all relevat papers i the field ad thus may have missed those that came to a differet coclusio. I cotrast, a recet systematic review of the evidece for geeral health-related beefits of exposure to ature used a more systematic search strategy (Bowler et al. 2010). Cosequetly, it icluded a broader evidece base ad also icluded a formal appraisal of study quality i a attempt to weigh the relative importace of differet ivestigatios. From the eight studies usig cogitive measures of assessmet, a meta-aalysis of five, focusig o

5 JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH, PART B 3 postexposure measures, supported ART. However, the three better desiged studies, measurig cogitive performace both before ad after exposure, demostratedomarkedevideceofimprovemetsfollowig exposure to ature. A umber of features of the Bowler et al. (2010) systematic review are importat. First, the ivestigatios icluded for the cogitive aspect of the review are differet from those reviewed by Kapla ad Berma (2010), suggestig the eed for a systematic review of all appropriate studies. Secod, ivestigatios usig subjective measures of directed attetio, such as paretal reports of childre s ability to cocetrate, were icluded. A more robust test of the theory would focus o those studies usig objective measures. Third, ad partly because of the limited umber of ivestigatios reviewed i both papers, there was little opportuity to examie whether some attetio measures were more sesitive to exposure to atural eviromets tha others. All of the measures may be cosidered as tryig to measure the same uderlyig costruct: directed attetio capacity. As with ay measuremet tool, each is subject to measuremet error ad might be more or less effective. Moreover, sice each measure may be tappig ito a slightly differet aspect of directed attetio capacity (such as alertig, orietatig, or executive fuctios), cosiderig data o the effects of ature o differet types of measure may shed light o the precise mechaisms by which ature may restore attetioal processes (Joides et al. 2008). The aim of the curret systematic review was to idetify, select, appraise, ad sythesize the evidece for ART amog studies that used experimetal ad quasi-experimetal approaches ad objective measures of attetio. A larger sample of studies was icluded ( = 31) tha was the case i either of the previous reviews. The ivestigatios were also critically appraised ad meta-aalyzed where possible. Such meta-aalysis is cosistet with Gifford s (2014) call for better evidece sythesis i evirometal psychology. Methods This systematic review followed the geeral priciples published by the Cetre for Reviews ad Dissemiatio (2009). The predefied protocol is available o PROSPERO (Referece CRD ). Review Questio What is the relative attetio restoratio potetial of atural settigs compared to other settigs? Literature Search A search strategy was devised by the research team, led by our Iformatio Specialist (Aliso Bethel), ad captured cocepts of attetio restoratio, cogitive fuctio, ad atural versus other settigs. No suitable MeSH (Medical Subject Headigs) terms were idetified. No methods filters were used. The master search strategy (Table 1) was adapted ad ru i the followig electroic databases i July 2013: PsycINFO, MEDLINE, ad EMBASE (usig OVID); AMED, SPORT Discus, ad Eviromet Complete (usig EBSCOHost); ad Web of Kowledge (o Thomso). Referece lists of icluded studies were scrutiized for relevat ivestigatios. Forward citatio searches were udertake o icluded studies. All searches were coducted from 1989, whe semial ivestigatios o ART were published. Citatio searches were also performed i Web of Sciece usig these key refereces: Kapla (1995) ad Kapla ad Kapla (1989). Iclusio Criteria Studies were eligible for iclusio i the review if they met the followig criteria: Populatio: Ay. Itervetio ad comparators: Studies reportig a compariso of the effects of exposure to atural settigs ad other, oatural settigs. The defiitio of atural icluded real settigs (such as parks, forests, wilderess areas) ad virtual settigs (images or videos of similar settigs). The defiitio of oatural settigs icluded real settigs (such as city ceters, residetial areas, parkig lots) ad virtual oes (images or videos of similar settigs). Types of egagemet with these settigs icluded active (such as walkig or ruig) ad passive (such as lookig at the view from a widow).

6 4 H. OHLY ET AL. Table 1. Master search strategy as used i OVID Medlie. 1 attetio restorat*.tw. 2 (theory or hypothesis).tw. 3 (attetio restorat* adj1 (theory or hypothesis)).tw. 4 atur*.tw. 5 outdoor*.tw. 6 gree*.tw. 7 forest*.tw. 8 coditio*.tw. 9 settig*.tw or 5 or 6 or 7 or 8 or 9 11 eviro*.tw. 12 (eviro* adj2 (atur* or outdoor* or gree* or forest* or coditio* or settig*)).tw or 5 or 6 or 7 14 (settig* adj2 (atur* or outdoor* or gree* or forest*)).tw or restorat*.tw ad attet*.tw. 19 cogitive fuctio*.tw. 20 cocetrat*.tw or 19 or ((attet* or cogitive fuctio* or cocetrat*) adj3 ((eviro* adj2 (atur* or outdoor* or gree* or forest* or coditio* or settig*)) or (settig* adj2 (atur* or outdoor* or gree* or forest*)))).tw or urba settig*.tw. 25 everyday settig*.tw. 26 garde*.tw. 27 metal fatigue*.tw or 5 or 6 or 7 or 24 or 25 or 26 or or 18 or 19 or ((restorat* or attet* or cogitive fuctio* or cocetrat*) adj3 (atur* or outdoor* or gree* or forest* or urba settig* or everyday settig* or garde* or metal fatigue*)).tw. (4872) or or limit 32 to yr = Curret Outcomes: Objective measures of attetio capacity, for example the Digit Spa Forward or Backward. Study desig: All experimetal desigs icludig radomized cotrolled trials, quasi-experimetal studies (oradomized cotrolled trials; radomized or oradomized crossover trials) ad atural experimets. With the exceptio of atural experimets, oradomized studies were icluded if they recorded measures of attetio before ad after exposure to ature/o ature settigs. Ivestigatios were excluded if baselie measures were take after exposure had commeced because it was ecessary to establish baselie attetioal abilities. Other: Coferece proceedigs or dissertatios were icluded if there were sufficiet data to assess the risk of bias. No laguage restrictios were applied. Study Selectio All refereces idetified through the search strategy were uploaded ito ENDNOTE (X7, Thomso Reuters) ad duplicates were removed. Referece titles ad abstracts, where available, were idepedetly double screeed agaist the iclusio criteria (by Heather Ohly ad Ruth Garside/Aliso Bethel). Studies appearig to meet these were retrieved i full text. Oe article was published i Chiese ad this was professioally traslated. Full text screeig was completed idepedetly by two reviewers (Heather Ohly ad Ruth Garside) usig the same criteria. Discrepacies were resolved through discussio betwee reviewers. Data Extractio A stadardized, piloted data extractio sheet was developed i Excel to esure cosistecy betwee studies ad reviewers. Data extracted for each study icluded study desig, sample characteristics, settig characteristics (atural ad oatural), type of exposure ad egagemet, duratio of exposure, measures of attetio, ad duratio of follow-up. Authors were cotacted to clarify or supply missig data where ecessary. Data were idepedetly extracted by oe reviewer (Heather Ohly) ad checked by a secod (Ruth Garside/Be Wheeler/ Mathew White). Disagreemets were resolved by discussio, icludig the full team where ecessary. Quality Appraisal The overall quality of the icluded studies was assessed usig a combiatio of resources ad guidelies: quality idicators from the Cetre for Reviews ad Dissemiatio (2009); critical appraisal checklists from the Critical Appraisal Skills Programme (2013); ad quality assessmet tool for quatitative studies from the Effective Public Health Practice Project (2013). These tools aim to assist reviewers i idetifyigpotetialsourcesofbiasadmakeacosidered judgmet how robust the evidece may be.

7 JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH, PART B 5 A bespoke quality appraisal ratig system was developed usig 20 stadard idicators of robust study coduct cosidered relevat i a review cotext. The ratioale ad method of applyig some of these idicators is provided i Table 2. Each quality idicator used the followig ratigs: yes = 2; partial = 1; o = 0; uclear = 0. To accommodate the fact that ot all questios were applicable for all study desigs, for example, questios about appropriate radomizatio, all studies were rated overall usig a percetage score based oly o applicable criteria. Overall quality assessmet was give as low (0 33%), moderate (34 66%), or high (67 100%). Give chagig stadards relatig to methods reportig ad limited word couts for may jourals, first authors of icluded papers were cotacted where a idicator had iitially bee scored uclear ( = 24). They were asked to provide more iformatio regardig the study, ad these uclear idicators i particular, to aid a more iformed assessmet of the papers. Of the 24 requests, 9 resposes with authors were received providig further details of study desig. Whether or ot authors respoded to our request is recorded i Table 4 (show later). Data Sythesis Radom effects meta-aalysis models were fitted usig stadard methods, i which iverse variace is used to weight idividual study results, to pool the effect estimates across ivestigatios. The meta-aalyses compared attetio outcomes at follow-up betwee groups exposed to atural settigs (itervetio) ad groups exposed to oatural settigs (cotrol) (Sutto et al. 2000). Summary data, the mea ad stadard deviatio of the outcome, ad sample size i each group for each study were used i the meta-aalysis, with pooled results reported as mea differeces (itervetio mius cotrol). Data were pooled from ivestigatios that used the same measures of attetio ad use the same outcome (some attetio measures have multiple associated outcomes). Care was take ot to double cout participats, for example, i crossover trials whe participats completed the same walk twice, aloe ad with a fried (Johasso, Hartig, ad Staats 2011). Oearticleicludedthreeseparatestudieseach with idepedet samples (Berto 2005). The first ivestigatio compared two groups, oe viewig atural images ad the other viewig urba images. The secod study had oly oe group, viewig geometric images, which were compared with data from the first ivestigatio. As the urba group from the first study ad the geometric group from the secod were idepedet, their results were combied before beig pooled with the third ivestigatio i the metaaalysis. Noe of the studies that measured outcomes at baselie reported usig the correct method to adjust for baselie imbalace, aalysis of covariace (ANCOVA) (Vickers ad Altma 2001). Cosequetly, all meta-aalyses were carried out usig data at follow-up oly. The mai meta-aalyses icluded all studies regardless of the level of baselie imbalace. Ivestigatios for which the mea differece betwee the groups i outcome score at baselie was greater tha oe-teth of the stadard deviatio i the cotrol arm (i.e., effect size of 0.1) were cosidered to have imbalace at baselie. Cohe (1992), i his summary of effect sizes i behavioral sciece studies, used a threshold of 0.2 to defie a small effect size. Sesitivity aalyses were also coducted i which oly those ivestigatios that had low levels of baselie imbalace were icluded, to illustrate the potetial impact of imbalaced experimets o results of the meta-aalyses. Data aalysis was carried out usig Stata 13 ad Review Maager (RevMa 5.2). Where studies could ot be meta-aalyzed, as they cotaied outcomes ot shared with other ivestigatios, or where isufficiet data were supplied, results are described arratively. Results Search Results Searches idetified 10,979 uique records. Twety-four articles met the iclusio criteria (Figure 1). Some of these articles reported results from more tha oe ivestigatio, so 31 separate studies were icluded. Give the complexity of the tables ad figures i this sectio, refereces are preseted usig oly the first author s ame ad the date, to simplify data presetatio.

8 6 H. OHLY ET AL. Table 2. Quality appraisal ratig system for selected idicators. Quality idicators Ratioale Yes Partial No Uclear Radom allocatio to groups/coditio order Radomizatio procedure appropriate Groups balaced at baselie (attetio scores) Participats blid to research questio Based o the scietific defiitio of radomizatio for the purpose of allocatio to eviromet groups. Failure to properly radomize has bee show to be associated with icreased levels of effect i cotrolled cliical trials (Jüi, Altma et al. 2001). Effect sizes were calculated to show whether groups were balaced or imbalaced at baselie i terms of attetio scores (or i some cases study authors provided this ifo). If participats were aware of the purpose of the study or hypothesis, this may have bee a source of bias i favor of the itervetio group through attractig a self-selected sample of those for whom the questio had resoace or ifluecig their experiece of itervetio ad cotrol exposures. Radom allocatio to groups (or coditio order i studies with withi-subject desigs). Appropriate method/tools of radomizatio used. A effect size <0.1 implies that groups were balaced at baselie (i.e., similar attetio scores). Therefore both groups have similar potetial to improve their attetio scores. Participats were ot aware of the research questio, ad/or may have bee give vague iformatio about the ature of the study. NA Noradom allocatio to groups. I atural experimets, where participats had previously bee radomly allocated to housig, this was ot classed as radom allocatio to eviromet groups because it was ot withi the experimet s cotrol. NA Iappropriate methods/tools of radomizatio used. Multiple attetio outcomes reported, of which some were balaced ad others were imbalaced at baselie. A effect size >0.1 implies that groups were imbalaced at baselie (i.e., dissimilar attetio scores). NA Participats were aware of the research questio ad specifically its focus o attetio outcomes. Method of allocatio ot clearly stated. Method/tools of radomizatio ot clearly stated. Data eeded to calculate effect size (baselie meas ad/or stadard deviatios) ot reported. Awareess or blidess to research questio ot clearly stated. (Cotiued)

9 JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH, PART B 7 Table 2. (Cotiued). Quality idicators Ratioale Yes Partial No Uclear Demostrated eed for attetio restoratio Cosistecy of itervetio (withi ad betwee groups) Normal or high attetio scores at baselie would limit the potetial for a exposure to ature to improve attetio (i.e., ceilig effect). Betwee-group cosistecy is importat because some of the experimetal studies ivolved participats completig the same activity i two or more differet settigs, i.e., active cotrol rather tha placebo cotrol. Ay differeces betwee groups (other tha the settig) may iduce performace bias ad lead to false results. For studies that ivolved viewig images of atural ad other settigs, aspects assessed for cosistecy icluded umber of images, duratio of exposure, locatio ad coditios. Study populatios with diagosed medical coditios that affect attetio were cosidered to have demostrated eed for attetio restoratio, for example, childre with ADHD. Some studies used a metal loadig task to iduce attetio fatigue prior to exposure to atural/other settigs. This was oly cosidered to have fully demostrated eed for attetio restoratio if measures of attetio were take before ad after the task (i.e., T1 loadig T2 exposure T3), thereby showig the extet of attetio depletio from baselie. Cosistecy of itervetio clearly described. Takig atural vs. urba walkig studies as example, withi-group cosistecy might iclude the walkig route, day of the week ad time of day, so that traffic volume is similar for each participat completig the urba walk. Betwee-group cosistecy might iclude the distace, speed, umber of walkers, talkig ad other coditios of the walks. Some studies used a guide to esure that a defied route ad pace were adhered to ad that coversatio/ distractios were kept to a miimum. Studies that measured attetio after the metal loadig task but ot before (i.e., loadig T1 exposure T2) were assiged partial because, although this sequece does ot show the effectiveess of the metal loadig task, it does show the impact of the itervetio. Some attempt to esure cosistecy. For example, some atural vs. urba walkig studies attempted to esure compliace by sedig participats out with maps or global positioig system (GPS); however, i some cases it was ot clear whether compliace was actually checked. Studies that measured attetio before the metal loadig task but ot after (i.e., T1 loadig exposure T2) were assiged o because this sequece does ot show the effectiveess of the metal loadig task ad the impact of the itervetio o depleted attetio is uclear. Lack of cosistecy withi ad/or betwee groups. For example, some itervetios were homebased ad self-directed, where participats chose from a rage of possible activities. I the atural experimet studies, participats may have lived i their curret home for varyig periods of time, ad may have had differet levels of exposure to ature outside the home. Study populatios may or may ot have depleted levels of attetio (e.g., schizophreia patiets) ad this was ot clearly stated. Some study authors may have cosidered it plausible that subjects were depleted but this was ot demostrated. Cosistecy of itervetio ot clearly described. (Cotiued)

10 8 H. OHLY ET AL. Table 2. (Cotiued). Quality idicators Ratioale Yes Partial No Uclear Outcome assessors blid to group allocatio Cosistecy of data collectio Statistical aalysis methods appropriate for study desig It has bee repeatedly show i cotrolled trials that lack of assessor blidig may lead to biased assessmet ad iflated effect sizes (Schulz et al. 1995; Jüi, Altma et al. 2001). However, this kid of detectio bias may be less problematic where objective outcome measures (such as attetio tests) are used. This icludes cosistecy withi groups ad betwee groups. I order to demostrate the effect of ature o attetio capacity, statistical compariso of the mea chage i attetio capacity betwee groups was expected (i.e., ANOVA or ANCOVA time eviromet). For atural experimets, baselie measures were ot collected ad this type of aalysis would ot be possible; therefore compariso betwee groups after the exposure (e.g., t-test) was cosidered appropriate. Assessor blidess clearly stated. NA Assessors were clearly ot blid to group allocatio, for example, if oe researcher led the group activities ad admiistered the attetio tests. Cosistecy of data collectio clearly described. Withi-group cosistecy might iclude the pre post assessmet iterval, particularly i studies where participats were recruited at differet times across a wider study period ad self-maaged the itervetio phase at home (such as cacer patiets or pregat wome). Betweegroup cosistecy might iclude the locatio, coditios, ad timig of data collectio. All of these factors may ifluece the outcome of the attetio tests ad the extet to which ay chages over time (ad differeces betwee groups) are observed. Appropriate statistical aalysis methods used. Some attempt to esure cosistecy. For example, there may have bee some variatio i the pre post assessmet iterval, but the testig was doe i the same room with all other factors cosistet. Some doubt as to the appropriateess of the statistical aalysis methods used, such as correct choice of test but icorrect use of data (e.g., collapsig three time poits). Lack of cosistecy withi ad/or betwee groups. Iappropriate statistical aalysis methods used. However, we recogise that accepted orms of statistical aalysis may have chaged sice the time of publicatio. Assessor blidess ot clearly stated. Cosistecy of data collectio ot clearly described. Lack of detail about data collectio methods geerally. Statistical aalysis methods ot clearly stated. (Cotiued)

11 JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH, PART B 9 Table 2. (Cotiued). Quality idicators Ratioale Yes Partial No Uclear Sample represetative of target populatio Studies were assessed for selectio bias (or samplig bias) icludig self-selectio, prescreeig or recruitmet from groups likely to show a better respose. If study participats are ot represetative of the target populatio, this may itroduce bias i favor of the itervetio group. Sample cosidered represetative of target populatio; recruitmet strategy icluded measures to reduce selectio bias. NA Sample ot cosidered represetative of target populatio. For example, studets erolled o evirometal courses such as forestry would be expected to show preferece for atural eviromets, which may icrease the likelihood of experiecig restoratio effects i atural eviromets relative to other types of eviromets. Isufficiet iformatio about the sample ad how it was recruited to make a judgmet about represetativeess.

12 10 H. OHLY ET AL. Records idetified through database searchig (=15443) Duplicate records idetified (=4464) Records screeed by title ad abstract (=10979) Records excluded based o title ad abstract (=10941) Records icluded based o title ad abstract (=38) Full text uobtaiable (=1) Full text articles screeed for eligibility (=41): Idetified from electroic search (=37) Idetified from had searchig (=4) Articles excluded based o full text (=17) with reasos: No objective measure of attetio (=6) No ature/other settig compariso (=5) No repeated measure of attetio ad participats ot radomised (=3) Dual publicatio of same data (=2) Baselie measures take after exposure to ature (=1) Articles icluded (=24) Studies or experimets icluded withi articles (=31) Figure 1. PRISMA flow chart. Study Characteristics The 31 icluded studies were from Europe, the Uited States, ad Asia, ad varied i terms of experimetal desig, sample characteristics, ad study duratio, as well as the type ad extet of exposure to ature (Tables 3A to 3D). Study desigs icluded 16 radomized cotrolled trials (RCT) from 12 articles (Berto 2005; Che, Lai, ad Wu 2011; Cimprich ad Rois 2003;Hartigetal. 1996; 2003; Hartig, Mag, ad Evas 1991; Lauma, Gärlig, ad Stormark 2003; Mayer et al. 2009; Perkis, Searight, ad Ratwik 2011; Rich 2008; Stark 2003; va de Berg, Koole, ad va der Wulp 2003); 7 radomized crossover trials from 6 articles (Berma et al. 2008; 2012; Bodi ad Hartig 2003; Johasso, Hartig, ad Staats 2011; Shietal.2011; Taylor ad Kuo 2009); 3 atural experimets (Kuo 2001; Taylor, Kuo, ad Sulliva 2002; Teesse ad Cimprich 1995); 3 oradomized cotrolled trials (Berto 2005; Hartig, Mag, ad Evas 1991; Wu et al. 2008); ad 2 oradomized crossover trials (Ottosso ad Grah 2005; va de Berg ad va de Berg 2011). Study populatios icluded childre, studets ad adults. Some samples were of idividuals with

13 JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH, PART B 11 Table 3A. Characteristics of icluded studies RCT desig; actual exposures (or mixed actual/virtual). Study Author, year () a desig Coutry ad settig Cimprich, 2003 RCT Uited States Uiversity medical ceter Hartig, 2003 RCT Uited States Uiversity ad local area Hartig, 1991 (2) RCT Uited States Uiversity ad local area Mayer, 2009 (1) RCT Uited States Uiversity Mayer, 2009 (2) RCT Uited States Uiversity Perkis, 2011 RCT Uited States Uiversity Stark, 2003 Cluster RCT Uited States Preatal classes Sample characteristics: geder, mea age, populatio, ethicity, ad s/e status if reported % female 53.8 years Patiets with ewly diagosed breast cacer (with surgery as primary treatmet pla) 86% White % male 20.8 years Studets % male 20 years Studets 76 29% male Mea age ot reported Studets 92 30% male Mea age ot reported Studets 26 27% male Age rage years Mea age ot reported Studets % female 29.1 years Pregat wome i the third trimester 94.7% White Note. Outcome measures listed i alphabetical order, ot the order i which they were admiistered. a Experimet umber i paretheses; each experimet has distict sample; s/e = socioecoomic. Itervetio characteristics: activity, settig (each group) ad duratio of exposure Attetio measures (objective) Home-based, patiet-led program of ature activities Cotrol group logged relaxatio time 120 mi per week (ature activities) Baselie follow-up period approx. 36 days (pread postsurgery) Sittig, atural view; the walkig, atural (ature reserve) Sittig, o view; the walkig, urba (city streets) 1 hour (10 mi passive; 50 mi active) Walkig, atural (regioal park) Walkig, urba (city cetre) Readig magazies, comfortable laboratory settig 40 mi Walkig, atural (woods/creek) Walkig, urba (dowtow) 10 mi Walkig, atural (woods) Watchig video, atural (woods) Watchig video, urba (busy streets) 10 mi Walkig, atural (woods) Walkig, urba (residetial/busiess) Walkig, urba (parkig lot) 20 mi Outdoor restorative activities Alterative sessio o the discomfort of pregacy 120 mi per week (outdoor activities) Baselie follow up period varied days Digit Spa Backward Digit Spa Forward Necker Cube Patter Cotrol Trail Makig Tests A Trail Makig Test B Necker Cube Patter Cotrol Search ad Memory Test Proofreadig Task Memory Loaded Search Task (similar to Search ad Memory Task) Memory Loaded Search Task (similar to Search ad Memory Task) Digit Spa Backward Digit Spa Forward Logical Memory Category Matchig Digit Spa Backward Digit Spa Forward Errors Scale Trail Makig Tests A Trail Makig Test B

14 12 H. OHLY ET AL. Table 3B. Characteristics of icluded studies RCT desig; virtual exposures. Author, year () a Study desig Coutry ad settig Berto, 2005 (1) RCT Italy Uiversity Berto, 2005 (3) RCT Italy Uiversity Che, 2011 (1) RCT Chia Seior secodary school Sample characteristics: geder, mea age, populatio 32 50% male 23 years Studets 32 50% male 22 years Studets 48 42% male Mea age ot reported Studets Hartig, 1996 (1) RCT Swede Uiversity ad high schools % male 21.4 years Studets Hartig, 1996 (2) RCT Swede Uiversity Lauma, 2003 RCT Norway Uiversity Rich, 2008 (1) RCT Uited States Uiversity Rich, 2008 (2) RCT Uited States Uiversity va de Berg, 2003 RCT The Netherlads Uiversity 18 50% male 27.4 years Studets % female Age rage years Mea age ot reported Studets % male Mea age ot reported Studets 36 42% male Age rage years Mea age ot reported Studets % male (after exclusios for = 106) 21.9 years Studets Note. Outcome measures listed i alphabetical order, ot the order i which they were admiistered. a Experimet umber i paretheses; each experimet has distict sample; s/e = socioecoomic Itervetio characteristics: activity, settig (each group) ad duratio of exposure Attetio measures (objective) Viewig images, atural Viewig images, urba 25 images 15 sec each Viewig images, atural Viewig images, urba 25 images duratio of their choice Viewig images, atural Viewig images, city Viewig images, urba ightscape Viewig images, sports 10 images 15 sec each Watchig simulated walk, atural (trees) Watchig simulated walk, urba (city) No simulated walk (cotrol) 80 slides 10 sec each (13.5 mi) Watchig simulated walk, atural (trees) Watchig simulated walk, urba (city) 80 slides maually (12 mi) Watchig video, atural (islad waterside) Watchig video, urba (city streets) 80 scees 15 sec each Sustaied Attetio to Respose Test Sustaied Attetio to Respose Test Colored umber pictures Search ad Memory Task Search ad Memory Task Poser s Attetio Orietig Task (ote: o raw data ad comparisos focus o differet types of stimuli; therefore ot reported i Table 5) Lookig at view, atural (forest) Lookig at view, urba (buildigs) No view 1 mi Readig magazies, room with plats Readig magazies, room with other objects 10 mi Vigilace Task Stroop Colour-Word Test Digit Spa Backward Watchig simulated walk, atural (forest with or without water) Watchig simulated walk, urba (city with or without water) 7 mi D2 metal cocetratio test

15 JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH, PART B 13 Table 3C. Characteristics of icluded studies Other desigs; actual exposures. Author, year () a Study desig Coutry ad settig Berma, 2008 (1) Radomized crossover trial Uited States Uiversity Sample characteristics: geder, mea age, populatio, ethicity, ad s/e status if reported 38 39% male 22.6 years Studets Berma, 2008 (2) Radomized crossover trial Uited States Uiversity 12 33% male 24.3 years Studets Berma, 2012 Radomized crossover trial Bodi, 2003 Radomized crossover trial Johasso, 2011 Radomized crossover trial Uited States Uiversity ad local area Swede Ruig club Swede Uiversity 20 40% male 26 years Adults diagosed with major depressive disorder (MDD) 12 50% male 39.7 years (males) 37.0 years (females) Ruers 20 50% male 24.2 years (males) 22.4 years (females) Studets Shi, 2011 Radomized crossover trial South Korea Uiversity 60 58% male 23.3 years Studets Taylor, 2009 Radomized crossover trial Uited States 25 88% male (after exclusios for = 17) 9.2 years Childre diagosed with ADHD Hartig, 1991 (1) Noradomized cotrolled trial Wu, 2008 (1) Noradomized cotrolled trial Uited States Trailheads ad local clubs Taiwa Public psychiatric cetre 68 62% male 35.9 years (G1) 29.2 years (G2) 31.6 years (G3) Experieced backpackers 23 72% male Mea age ot reported Schizophreia patiets Itervetio characteristics: activity, settig (each group), duratio of exposure, ad washout period (crossover oly) Walkig, atural (park) Walkig, urba (dowtow) mi Two walks, 1 week apart Viewig images, atural (Nova Scotia) Viewig images, urba (dowtow) 50 images i 10 mi Two sessios, 1 week apart Walkig, atural (park) Walkig, urba (dowtow) mi Two walks, 1 week apart Ruig, atural (park) Ruig, urba (city streets) 60 mi Two rus, 1 week apart Walkig, atural (park) Walkig, urba (streets) 40 mi Four walks, 1 week apart (atural with fried; urba with fried; atural aloe; urba aloe) Walkig, atural (park) Walkig, urba (city streets) mi Two walks, 1 week apart Walkig, atural (urba park) Walkig, urba (dowtow) Walkig, urba (eighborhood) 20 mi Three walks, 1 week apart Wilderess backpackig vacatio Nowilderess vacatio No vacatio 4 7 days (vacatio groups) Horticulture activities (idoors ad outdoors) Regular hospital activities like watchig movies, sigig, drawig, cookig (idoors) 90 mi per week 15 classes Attetio measures (objective) Digit Spa Backward Attetio Network Test Digit Spa Backward Digit Spa Backward Combied Digit Spa Backward ad Forward Symbol Digit Modalities Test Symbol Substitutio Test Trail Makig Test B Digit Spa Backward Stroop Colour-Word Test Symbol Digit Modalities Test Vigilace Task (Note: Oly DSB reported) Proofreadig Task Chu s Attetio Test (Cotiued)

16 14 H. OHLY ET AL. Table 3C. (Cotiued). Author, year () a Study desig Coutry ad settig Ottosso, 2005 Noradomized crossover trial Swede Residetial care home Sample characteristics: geder, mea age, populatio, ethicity, ad s/e status if reported 17 87% female (after exclusios for = 15) 86 years Elderly residets of the care home va de Berg, 2011 Noradomized crossover trial The Netherlads Two care farms 12 83% boys 12.8 years Childre diagosed with ADHD Kuo, 2001 Natural experimet Taylor, 2002 Natural experimet Uited States Ier city commuity Uited States Ier city commuity % female 34 years Heads of household; Africa America residets of ier city housig developmet % boys 9.6 years Childre; Africa America residets of ier city housig developmet Teesse, 1995 Natural experimet Uited States Uiversity 72 42% male 20 years Studets Note. Outcome measures listed i alphabetical order, ot the order i which they were admiistered. a Experimet umber i paretheses; each experimet has distict sample; s/e = socioecoomic. Itervetio characteristics: activity, settig (each group), duratio of exposure, ad washout period (crossover oly) Leisure time outside (terrace ad gardes) Leisure time iside (ow room ad shared space) 1h Two sessios, 14 days apart Buildig a cabi, atural (woodlad) Walkig expeditio, urba (quiet eighborhood) 1 hour Two activities, 1 day apart Livig ear high levels of vegetatio ( gree ) Livig ear low levels of vegetatio ( barre ) High level of ear-home ature ( gree view from apartmet) Low level of ear-home ature ( barre view from apartmet) At least 1 year livig i curret locatio All atural view from dormitory Mostly atural view from dormitory Mostly built view from dormitory All built view from dormitory Attetio measures (objective) Digit Spa Backward Digit Spa Forward Necker Cube Patter Cotrol Symbol Digit Modalities Test Test of Everyday Attetio for Childre Digit Spa Backward Alphabet Backward Category Matchig Delayed Gratificatio Task Digit Spa Backward Matchig Familiar Figures Test Necker Cube Patter Cotrol Symbol Digit Modalities Test Stroop Colour-Word Test Digit Spa Backward Digit Spa Forward Necker Cube Patter Cotrol Symbol Digit Modalities Test

17 JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH, PART B 15 Table 3D. Characteristics of icluded studies Other desigs; virtual exposures Author, year () a Berto, 2005 (2) Study desig Noradomized cotrolled trial Coutry ad settig Italy Uiversity Sample characteristics: geder, mea age, populatio, ethicity, ad s/e status if reported 64 50% male 23 years Studets Note. Outcome measures listed i alphabetical order, ot the order i which they were admiistered. a Experimet umber i paretheses; each experimet has distict sample; s/e = socioecoomic. Itervetio characteristics: activity, settig (each group), duratio of exposure, ad washout period (crossover oly) Viewig images, atural Viewig images, urba Viewig geometric images Note: Two groups from Berto 2005 (1) 25 images 15 sec each Attetio measures (objective) Sustaied Attetio to Respose Test psychological coditios such as attetio deficit hyperactivity disorder (ADHD), depressio, or schizophreia (Berma et al. 2012; Taylor ad Kuo 2009; vadebergadvadeberg2011;wuetal.2008), lower icome groups such as Africa America residets of a ier city housig developmet (Kuo 2001; Taylor, Kuo, ad Sulliva 2002); or participats experiecig other circumstaces that, it is suggested, might ifluece their attetio capacity, such as pregacy or breast cacer (Cimprich ad Rois 2003; Stark2003). The remaider of the samples had ormal cogitive fuctio. Study duratio ad itesity varied, from less tha a hour of exposure i cotrolled coditios, to multiple days or weeks of exposure i real-life settigs. The logest exposures were see i the atural experimets, where participats had bee exposed to their surroudigs for moths or years (Kuo 2001; Taylor, Kuo, ad Sulliva 2002; Teesse ad Cimprich 1995). Ivestigatios used various cogitive tests. Some studies ivolved actual exposure to ature: either through active egagemet (walkig, ruig, or other activities)(berma et al. 2008; 2012; Bodi ad Hartig 2003; Cimprich ad Rois 2003; Hartig et al. 1996; Hartig, Mag, ad Evas 1991; Johasso, Hartig, ad Staats 2011; Mayer et al. 2009; Perkis, Searight, ad Ratwik 2011; Shietal. 2011; Stark 2003; Taylor ad Kuo 2009; va de Berg ad va de Berg 2011; Wu et al.2008) or passive egagemet (restig outside or livig with a view) (Kuo 2001; Ottosso ad Grah 2005; Rich 2008; Taylor, Kuo, ad Sulliva 2002; Teesse ad Cimprich 1995). Other ivestigatios ivolved virtual exposure to ature; this was exclusively passive egagemet (watchig video or viewig images) (Berma et al. 2008; Berto2005; Che, Lai, ad Wu 2011; Hartigetal. 1996; Lauma, Gärlig, ad Stormark 2003; Rich 2008; va de Berg, Koole, ad va der Wulp 2003). Most studies had a compariso group that ivolved equivalet exposure to a oatural (urba or idoor) settig. Four studies used a placebo cotrol settig ivolvig relaxatio time or usual activities (Cimprich ad Rois 2003; Hartig et al. 1996; Hartig, Mag, ad Evas 1991; Rich 2008). Quality scores varied from 22.5 to 75% (Table 4). Seve of the 31 icluded studies were classified as high quality (scorig %), while 22 were classified as moderate (scorig 34 66%) ad 2 were classified as low quality (scorig 0 33%). The quality idicators reflected overall experimetal quality ad also how well the study aswered our review questio, which may ot have bee the mai focus of the idividual studies. Idicators that few ivestigatios reported clearly were power calculatio, radomizatio procedure, whether participats were blid to the research questio, demostrated eed for attetio restoratio, whether outcome assessors were blid to group allocatio, ad whether the sample was represetative of the target populatio. Evidece for Effects of Nature o Attetio Capacity Some ivestigatios reported results for subgroups, such as me/wome (Bodi ad Hartig 2003), task/o task (Hartig et al. 1996; 2003), ad aloe/with fried (Johasso, Hartig, ad Staats 2011). Oe study compared oe atural group (walkig i woods) ad two oatural groups (walkig i eighborhood ad walkig i parkig lot), but oly preseted attetio scores for the sample as a whole (Perkis, Searight, ad Ratwik 2011).

18 16 H. OHLY ET AL. Table 4. Idicators of quality of icluded studies. Quality idicators Cimprich, 2003 Hartig, 2003 RCT desig; real exposures RCT desig; virtual exposures Hartig, 1991 (2) Mayer, 2009 (1) Mayer, 2009 (2) Perkis, 2011 Stark 2003 Study desig Power calculatio reported No No No No No No No No No No No No No No No No Iclusio criteria reported Yes Yes Pa. No No No Yes No No No Yes No No No No No Idividual level allocatio Yes Yes Yes Yes Pa. Yes No Yes Yes Yes No Yes Yes Yes Yes Yes Radom allocatio to groups/ Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes coditio order Radomizatio procedure U. Yes Yes U. U. Yes U. U. U. Yes U. U. U. U. U. U. appropriate Cofouders Groups similar Pa. Yes Yes U. U. Yes Yes U. U. U. Yes Yes U. U. U. U. (sociodemographic)* Groups balaced at baselie No Yes Pa. U. U. No Pa. Pa. Pa. No No No U. U. U. U. (attetio scores) Participats blid to research No Yes Yes U. Yes Yes No U. U. U. Yes U. U. U. U. U. questio Itervetio itegrity Demostrated eed for attetio No Pa. U. No No No No No No Yes U. U. Pa. No No No restoratio Clear descriptio of itervetio Yes Yes Yes Yes Yes Pa. Yes Yes Yes Yes Yes Yes Yes Pa. Yes Yes ad cotrol Cosistecy of itervetio No Yes Pa. Pa. Yes Pa. No Yes Yes Yes Yes Pa. Yes U. Yes Yes (withi ad betwee groups) Data collectio methods Outcome assessors blid to U. No No U. U. No U. U. U. U. No No U. No No U. group allocatio Baselie attetio measures Yes Yes Yes No No Yes Yes Yes Yes Yes No No Yes No No No take before the exposure Cosistecy of data collectio Pa. Yes Pa. U. U. Yes Yes Yes Yes Yes Yes Yes Yes U. Yes Yes Aalyses All attetio outcomes reported Yes Pa. Pa. Yes Yes No No Yes Yes Yes Yes Yes No No No No (meas ad SD/SE) All participats accouted for Yes Yes Yes U. Yes Yes Yes Yes Yes Yes No Yes Yes U. U. Yes (i.e., losses/exclusios) ITT aalysis coducted (all data No No No U. No No Yes Yes Yes No No Yes No U. U. No icluded after allocatio) Idividual level aalysis Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Statistical aalysis methods Yes Yes No Yes Yes Pa. Yes No No Pa. Yes U. Yes Yes Yes Yes appropriate for study desig Exteral validity Sample represetative of target No U. U. U. U. U. No U. U. Yes U. U. U. U. U. U. populatio (Cotiued) Berto 2005 (1) Berto 2005 (3) Che, 2011 (1) Hartig, 1996 (1) Hartig, 1996 (2) Lauma, 2003 Rich 2008 (1) Rich 2008 (2) va de Berg, 2003