RETRACTED. RETRACTED: Sluggish Cognitive Tempo, Internalizing Symptoms, and Executive Function in Adults With ADHD

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1 Removal Notice Journal of Attention Disorders 1 The Author(s) 2017 Reprints and permissions: sagepub.com/journalspermissions.nav DOI: / journals.sagepub.com/home/jad Leikauf, J. E., & Solanto, M. V. (2016). Sluggish Cognitive Tempo, Internalizing Symptoms, and Executive Function in Adults With ADHD. Journal of Attention Disorders. Advance online publication. doi: / The article was revised after its original publication in OnlineFirst. The original publication has now been removed, and the final OnlineFirst version of the article can be accessed at

2 659361JADXXX / Journal of Attention DisordersLeikauf and Solanto research-article2016 Article : Sluggish Cognitive Tempo, Internalizing Symptoms, and Executive Function in Adults With ADHD Journal of Attention Disorders 2017, Vol. 21(6) NP1 NP11 The Author(s) 2016 Reprints and permissions: sagepub.com/journalspermissions.nav DOI: / journals.sagepub.com/home/jad John E. Leikauf 1 and Mary V. Solanto 1 Abstract Objective: Symptoms of sluggish cognitive tempo (SCT) have been considered a potential subset of symptoms of ADHD, predominantly inattentive presentation (ADHD-I), or as a separate but related symptom dimension. We sought to characterize the relationships between SCT and both internalizing symptoms and executive functioning in adults with ADHD. Method: One hundred two adults diagnosed with ADHD completed clinical interviews and clinical rating scales. Hierarchical regression analyses were conducted to ascertain the independent predictive power of SCT symptoms for executive dysfunction after considering ADHD inattentive and hyperactive-impulsive symptoms and internalizing symptoms. Results: SCT was correlated with ADHD inattentive symptoms and dimensional measures of depression and anxiety symptoms, but not with clinical diagnosis of depression or anxiety disorder. SCT was independently predictive of executive function deficits over and above the effects of internalizing and ADHD symptoms. Conclusion: SCT in adults is associated with internalizing symptoms, ADHD inattentive symptoms, and, independently, with executive function deficits, particularly organization and problem solving. (J. of Att. Dis. XXXX; XX(X) XX-XX) Keywords ADHD, sluggish cognitive tempo, depression, anxiety, executive function Sluggish cognitive tempo (SCT) is a term for a cluster of symptoms that includes hypoactivity, drowsiness, daydreaminess, lethargy, and apathy, and that has been proposed to better characterize the clinical presentation of a subgroup of those with attention and concentration problems (Carlson, Lahey, & Neeper, 1986; McBurnett, Pfiffner, & Frick, 2001). SCT was considered for inclusion as a symptom domain of the Inattentive Subtype in the Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV; American Psychiatric Association [APA], 1994). Two symptoms were tested ( drowsy and daydreams ) and were ultimately not included because they were found to have high positive but low negative predictive validity for the inattentive dimension in the DSM-IV field trials (Frick et al., 1994). A third, forgetfulness, was also considered as a potential SCT symptom but was found to have both positive and negative predictive validity and so was included as an ADHD inattentive symptom in DSM-IV. Early factor analytic research revealed that SCT symptoms constituted a factor distinct from that of the inattentive and hyperactive-impulsive symptoms of ADHD and suggested that elevations on this factor uniquely characterized ADHD, Predominantly inattentive presentation (ADHD-I; McBurnett, Pfiffner, & Frick, 2001). Subsequent research partially corroborated these results, establishing that symptoms of SCT, as rated by parents and teachers, emerged as a separate, third factor when entered into analyses that included ratings of inattentive and hyperactive-impulsive symptoms of ADHD (Becker, Langberg, Luebbe, Dvorsky, & Flannery, 2014; Garner, Marceaux, Mrug, Patterson, & Hodgens, 2010; Lee, Burns, Snell, & McBurnett, 2014; Willcutt et al., 2014). A recent meta-analysis, considering 23 independent studies including 19,000 participants has confirmed that SCT constitutes a factor distinct both from the ADHD inattentive and hyperactive-impulsive symptom dimensions (Becker et al., 2016). In addition, and as predicted given the nature of the symptoms, SCT has been shown in several studies in children and in a recent metaanalysis to correlate more highly with the inattentive than the hyperactive-impulsive dimension of ADHD (Becker et al., 2016; Frick et al., 1994; Lee et al., 2014). The relationship of SCT to ADHD-I is not yet fully clear, however, with some studies finding higher SCT ratings in ADHD-I than ADHD, Combined presentation (ADHD-C) 1 Icahn School of Medicine at Mount Sinai, New York, NY, USA Corresponding Author: John E. Leikauf, Department of Psychiatry and Behavioral Sciences, Stanford University, 401 Quarry Rd., Stanford, CA 94305, USA. jleikauf@stanford.edu

3 NP2 Journal of Attention Disorders 21(6) (Garner et al., 2010; Willcutt et al., 2014), but also finding that ADHD-C had higher SCT ratings than did the controls (Willcutt et al., 2014). Moreover, dividing ADHD-I into subgroups with high versus low SCT symptoms did not yield corresponding differences in gender, age of onset, or parent ratings of internalizing or externalizing symptomatology (Harrington & Waldman, 2010). Rather unexpectedly, Barkley (2013) found more frequent cases of high SCT among children and adolescents with ADHD-C (55%) when compared with those with ADHD-I (31%) or ADHD, Predominantly hyperactive/impulsive presentation (ADHD-HI; 21%). Intriguingly, recent studies of community samples of children (Barkley, 2013) and adults (Barkley, 2012b) found that high SCT occurred in some participants in the absence of ADHD, which, the authors suggested, may indicate that SCT represents a separate disorder with high overlap with ADHD, rather than a subtype of ADHD. In summary, SCT symptoms appear to have a greater association with inattentive than with hyperactive/impulsive symptoms, but do not aid in differentiating ADHD-I from ADHD-C. SCT and Internalizing Symptoms in Children and Adolescents Research in children and adolescents has also addressed the possibility that SCT is a manifestation of anxiety or depression, which it phenotypically resembles. Symptoms of SCT emerged as a separate factor even when entered into analyses that included symptoms of anxiety and depression in addition to those of ADHD, indicating that SCT is not simply a proxy for these internalizing disorders in children (Willcutt et al., 2014). This finding was confirmed in metaanalysis (Becker et al., 2016). However, SCT does appear to co-occur with internalizing disorders in children with a greater frequency than does ADHD alone (Garner et al., 2010; Lee et al., 2014; Willcutt et al., 2014). Furthermore, the presence of SCT predicted internalizing symptoms and social problems even after controlling for its association with ADHD symptomatology (Becker & Langberg, 2013; Marshall, Evans, Eiraldi, Becker, & Power, 2014). In a study of children, inattentive ADHD symptoms and parentreported depression were uniquely associated with SCT symptoms, but child-reported depression did not carry an independent association with SCT (Garner, Mrug, Hodgens, & Patterson, 2013). Barkley (2013) compared groups of children/adolescents with SCT-only, ADHD-only, ADHD + SCT, and typical children and found that the two groups with SCT had higher rates of depression than typicals, which was not true for the ADHD-only group. The SCT groups did not, however, have higher rates of anxiety (Barkley, 2013). The conclusion thus far is that there is an association between SCT and internalizing disorders, particularly depression, but that they are not completely overlapping constructs. SCT and Executive Function (EF) in Children and Adolescents Several studies have examined the extent to which SCT contributes to the prediction of EF deficits in youth after accounting for inattentive symptoms. Using parent ratings on the Barkley Deficits in Executive Functioning Scale Children and Adolescents (-CA), a questionnaire measure of EF, Barkley showed that the set of Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM- 5; APA, 2013) ADHD inattentive symptoms explained by far the greatest proportion of the variance, with SCT contributing only a very small additional percentage approximately 5% of the variance on the self-organization/ problem-solving dimension (Barkley, 2012a, 2013). Similar results were reported by Becker and Langberg (2014), in a study of 52 adolescents with ADHD using the metacognitive index of the teacher- and parent-rated Behavior Rating Inventory of Executive Function (BRIEF), which encompasses initiation, working memory, planning, organization, and self-monitoring (Gioia, Isquith, Guy, & Kenworthy, 2000). However, a Spanish study of 76 youth aged 6 to 17 found that correlations between SCT and several EF domains measured on the BRIEF (emotional control, working memory, planning/organization, and organization of materials) remained significant after controlling for ADHD symptoms (Araujo Jiménez, Jané Ballabriga, Bonillo Martin, Arrufat, & Serra Giacobo, 2015). None of these three studies accounted for the effects of depression and anxiety in their regression analyses, but all found a modest independent correlation between SCT and some, but not all, domains of EF. Among studies that did consider internalizing comorbidity, a study of 165 children aged 7 to 11 with ADHD-I found a correlation between organization problems measured by the Children s Organizational Skills Scale and one of the three SCT factors sleepy/tired that remained significant after partialing out the effect of depression severity across both parent and teacher reports (Abikoff et al., 2013; McBurnett et al., 2014). A smaller study of children aged 7 to 12 compared 19 children with ADHD-I and SCT to 68 children with ADHD but not SCT and reported that children with SCT and ADHD-I had fewer problems with sustained attention but greater problems with EF as measured by the BRIEF (Capdevila-Brophy et al., 2014). After adjusting for anxiety and depression, only the relationship between high SCT and deficits in self-monitoring remained stronger than in the low SCT group. Contrasting with these findings are the results of several large studies using neuropsychological test measures of EF s, which did not find significant correlations with SCT (Bauermeister, Barkley, Bauermeister, Martinez, & McBurnett, 2012; Wahlstedt & Bohlin, 2010; Willcutt et al., 2014).

4 Leikauf and Solanto NP3 In summary, studies measuring EFs using self-report rating scales in children and young adults tend to find a relationship with SCT, though generally a weaker relationship than that between EF and ADHD-I symptoms. This relationship is not found when using neuropsychological tests of EF, which may reflect the lesser ecological validity of EF tests compared with EF rating scales in both children (Isquith, Roth, & Gioia, 2013) and adults (Barkley & Fischer, 2011; Barkley & Murphy, 2010). SCT in Adults Several studies have examined the relationship between SCT and EF in large samples of undergraduate psychology college students, and two have studied adults beyond college age. In a study of 768 college students, SCT emerged as a separate factor, independent of ADHD symptoms (Becker et al., 2014) and was associated with depression and anxiety in another study of 158 students (Flannery, Becker, & Luebbe, 2014). Furthermore, SCT predicted unique variance in social impairment, an effect that was mediated via emotional dysregulation (Flannery et al., 2014). Interestingly, Wood reported that high SCT occurred without ADHD in 9.8% of their sample of 458 students (Wood, Lewandowski, Lovett, & Antshel, 2014), consistent with the possibility that SCT may exist as a separate disorder. Two studies examined the relationship between SCT and EF in large samples of college students (Jarrett, Rapport, Rondon, & Becker, 2014; Wood et al., 2014). Symptoms of ADHD, depression, anxiety, as well as EF and SCT were assessed via self-report. Both studies showed that SCT contributed unique variance to EF subscales of Self-Organization/ Problem Solving and Emotional Self-Regulation on the Barkley Deficits in Executive Function Scale (; Jarrett et al., 2014), whereas ADHD inattentive symptoms more strongly predicted self-management to time. SCT contributed to the Total EF score more than (Wood et al., 2014) or equally (Jarrett et al., 2014) with ADHD-I. Jarrett et al. (2014) also tested participants on visual working memory, set-shifting, and attention and found no relationship between these neuropsychological test results and either SCT or ADHD symptoms. Only two studies of which we are aware have studied SCT in adults beyond college age. In one, Barkley (2012b) recruited a representative sample of 1,249 U.S. adults, between 18 and 96 years of age. Participants were divided into those with and without ADHD (on the basis of a self-rated scale of DSM-IV ADHD symptoms) and those high and low in SCT (based on a nine-item self-rated scale comprised of items from earlier studies of children). This procedure identified 46 participants with ADHD but without SCT and 39 with both ADHD and SCT. A subgroup of 33 was found to have SCT but not ADHD, corroborating findings in youth that suggested that SCT may occur without ADHD (Barkley, 2013). As was reported for children, SCT did not appear to sort strictly with the ADHD-I subtype, occurring in 68% of those with ADHD-I, 65% of those with ADHD-C, and 10% of those with ADHD-HI. Selfreported occupational impairment was higher in those with SCT-only than in those with ADHD-only and highest in those with both. Educational impairment was equivalent in those with SCT, with or without ADHD, and higher than in those with ADHD-only. More clearly than in youth, SCT conferred impairment in EF (on the ) over and above that associated with ADHD. Specifically, those with both ADHD and SCT were more impaired in time management, self-organization, self-restraint (inhibition), regulation of emotion, and motivation than were those with ADHD or SCT alone. A second study found a negative association between SCT and quality of life in a non-clinical, community sample of 983 adults (Combs et al., 2014). Although this study did not assess EF directly, the broad quality-of-life measure suggested the presence of functional impairment. These results, taken together, suggest that the symptoms of SCT negatively affect EF more in adults than in youth. However, the relationship with internalizing disorders is not yet clear. In summary, although SCT is relatively well-studied in children and adolescents, there is a paucity of data concerning ADHD in adults, particularly with respect to relationships with internalizing disorders and with executive functioning. Furthermore, because research to date in adults has measured SCT in population- or community-based samples, it is particularly important to examine these issues in clinically referred and comprehensively evaluated adults. We therefore tested the following hypotheses to better characterize SCT in a sample of clinically referred and diagnosed adults with ADHD: Given the nature of SCT and given previous research in children, we postulated that SCT would be more highly correlated with the inattentive dimension of ADHD symptoms than with the hyperactive/impulsive dimension. Based on studies in youth, and on our own clinical observations, we predicted that among clinically diagnosed adult participants with ADHD and high SCT, there would be a higher percentage of ADHD-I than among those with ADHD and low SCT. We predicted that adults with ADHD and high SCT scores would have both higher rates of clinical diagnosis of depression or anxiety and higher scores on dimensional ratings of internalizing disorders compared with adults with ADHD and low SCT scores. Finally, we hypothesized that SCT would predict greater impairments in EFs after controlling for severity of ADHD symptoms and internalizing symptomatology. Method Participants were drawn from among adults referred to, and comprehensively evaluated at, a specialty service for ADHD at a tertiary referral medical center in an urban

5 NP4 Journal of Attention Disorders 21(6) setting of a large metropolitan area. The institutional review board (IRB) at the medical center approved the study. Participants constituted all individuals evaluated between August 2012 and March 2014, who met criteria for a DSM-IV or DSM-5 diagnosis of ADHD via two unstructured clinical interviews that established current and lifetime symptoms of ADHD and other possible differential or comorbid diagnoses. In the first visit, evaluators ascertained current symptoms, context, and impairment. In the second, they obtained developmental, academic, and social history from childhood through adulthood to examine onset and trajectory of symptoms of ADHD and any other presenting symptoms (and associated impairment) to determine the relative primacy of ADHD and comorbid symptoms. Evaluations were performed by experienced staff clinicians. Most interviews were conducted prior to release of DSM-5, therefore Diagnostic and Statistical Manual of Mental Disorders (4th ed., text rev.; DSM-IV-TR; APA, 2000) definitions were used. The DSM-based clinical diagnosis of ADHD was corroborated by a T score equal to or greater than 63 (i.e., 1.3 SD above the mean) on the Conners Adult ADHD Rating Scale Self-Report Long Form (CAARS) Subscale E (CAARS-E), DSM-IV Inattentive Symptoms. Study participants did not include anyone with history of schizophrenia, bipolar disorder, or borderline personality disorder; history of neurological disorders such as epilepsy, mental retardation, or traumatic brain injury; active substance abuse; or report of active suicidal ideation. Of evaluated participants, one was deemed ineligible due to diagnosis of thought disorder (judged equivalent to psychotic disorder, not otherwise specified) and one for a history of traumatic brain injury. No evaluated participants met criteria for other exclusionary diagnoses. Eighteen participants were excluded because they did not meet ADHD and/ or \CAARS-E inclusion criteria. A depressive disorder was counted as present if a participant met criteria for any of the disorders that fall within the depressive disorders category in DSM-5 except depressive disorder due to another medical condition or Substance/ Medication-Induced Depressive Disorder. Similarly, an anxiety disorder was counted as present if a participant met criteria for any of the disorders that fall within the anxiety disorders category in DSM-5 except anxiety disorder due to another medical condition or substance/medication-induced anxiety disorder. All participants completed the following clinical rating scales: the CAARS, from which two subscales were used for this study CAARS-E and Subscale F, DSM-IV Hyperactive-Impulsive Symptoms (CAARS-F) (DSM-IV Hyperactive-Impulsive Symptoms; Conners, Erhart, & Sparrow, 1999); Barkley s nine-item SCT rating scale (Barkley, 2012a); the Beck Depression Inventory II (BDI-II; Beck, Steer, & Brown, 1996); and State-Trait Anxiety Inventory (STAI; Spielberger, Gorsuch, Lushene, Vagg, & Jacobs, 1983) as dimensional measures of internalizing disorder symptoms; and the Self-Report, from which all subscales were used: Self-Management to Time, Self- Organization/Problem Solving, Self-Motivation, Self- Regulation of Emotions, Total Executive Function (EF), and ADHD-EF index this last, index subscale indicates the likelihood that the respondent has ADHD (Barkley, 2011). All data analyses were conducted using SPSS software, Version 23. SCT was examined both as a categorical variable and as a continuous/dimensional variable. For SCT as a categorical variable, an SCT symptom was considered to be present if rated as 2 (pretty much) or 3 (very much) on a scale of 0 to 3. Those with five or more symptoms were considered high SCT. The validity of this division is supported by the fact that it matched the criterion identified as the 95th percentile for SCT symptom burden in a recent large, non-clinical sample of adults and therefore was used as a cutoff for high SCT in that study (Barkley, 2012b). High and low SCT groups were compared on demographic characteristics and categorical diagnoses using Pearson s chi-square. Pearson correlations were conducted to examine the relationships among SCT, ADHD symptoms, internalizing symptoms, and executive dysfunction. Hierarchical linear regression was conducted to ascertain the predictive utility of SCT vis-à-vis executive dysfunction after considering the contributions of ADHD symptoms and internalizing symptoms. Independent variables were forced into the analysis in the following order: Block 1: Age; Block 2: CAARS-E; Block 3: CAARS-F; Block 4: Internalizing symptoms as captured in the total scores on the BDI-II and STAI indices; and Block 5: SCT. A separate model was constructed for each of the EF subscales. Results Demographic statistics are reported in Table 1. The final sample consisted of 102 participants ranging in age from 18 to 64 (M = 37.8, SD = 11.6 years), of whom 48 had a symptom score less than 5 and were considered low SCT. The remaining 54 participants were considered high SCT. The mean SCT score in the low SCT group was (SD = 3.0), while the mean SCT score of the high SCT group was (SD = 3.36). In the sample as a whole, 62 (61%) were classified as ADHD-I and 37 (36%) as ADHD-C. One participant had ADHD-HI and two had unspecified ADHD. Most participants (93%) self-identified as Caucasian, and 81% had at least a bachelor s degree. The high SCT group participants were significantly younger than the low-sct group: mean age was years (SD = 10.5 years) versus years (SD = 11.8 years), respectively, t(100) = 2.97, p =.004. Age was therefore used as a covariate in subsequent analyses. The high SCT group also had significantly fewer advanced degrees, but this was not included as a covariate because it was judged likely to be an outcome of SCT, given

6 Leikauf and Solanto NP5 Table 1. Demographic Characteristics. Characteristic Frequency (%) High SCT (n = 54) Low SCT (n = 48) Pearson χ 2 Gender Male 28 (52) 30 (63) Female 26 (48) 18 (37) Race/ethnicity Asian 1 (2) 3 (6) Black, non- 1 (2) 1 (2) Hispanic Black, Hispanic 0 0 White, non- 51 (94) 41 (86) Hispanic White, Hispanic 0 3 (6) Multiple 1 (2) 0 Education High school or 10 (19) 8 (17) equivalent Technical 1 (2) 0 Bachelor s 32 (59) 17 (35) Master s 8 (15) 10 (21) Doctorate or 3 (5) 12 (25) professional Unknown 0 1 (2) Marital status Married 22 (41) 27 (57) Divorced 4 (7) 2 (4) Never married 26 (48) 16 (33) Cohabiting 2 (4) 3 (6) Note. SCT = sluggish cognitive tempo. the previously reported functional impairments in adults (Barkley, 2012b; Combs, 2014). The groups did not differ significantly in gender, race/ethnicity, or marital status. High and low SCT groups were compared with respect to proportions of ADHD subtype diagnoses and of comorbid internalizing disorder diagnoses (Table 2). Rates of ADHD subtypes were closely comparable in the two groups: 41% and 31% for ADHD-C in the high and low SCT groups, respectively, versus 59% and 63% for ADHD-I. There was no significant difference between the low and high SCT groups in the proportions of individuals with depressive or anxiety disorders. The zero-order correlations between these variables are presented in Table 3. Results of hierarchical multiple regression analyses are presented in Table 4. Standardized beta coefficients associated with the full model equation for each variable are presented in Table 5. All variance inflation factor (VIF) values indicated acceptable levels of multicollinearity (1 < VIF < 4, for all independent variables across all models). Significance of the change in F (Table 4) indicated that after entering age, CAARS-E contributed p Table 2. Frequencies of ADHD and Internalizing Diagnoses in High and Low SCT Groups. DSM diagnosis Frequency (%) High SCT (n = 54) Low SCT (n = 48) Pearson χ 2 ADHD subtype Combined 22 (41) 15 (31) Predominantly 32 (59) 30 (63) Inattentive Hyperactive-impulsive 0 1 (2) Unspecified 0 2 (4) Internalizing disorders Depressive disorder 22 (41) 16 (33) Anxiety disorder 18 (33) 12 (25) Depressive or anxiety disorder 24 (44) 20 (42) Note. SCT = sluggish cognitive tempo; ADHD = Attention-Deficit/ Hyperactivity Disorder; DSM = Diagnostic and Statistical Manual. significantly to the models for all subscales and indices. CAARS-F added additional variance to the equations for self-organization/problem solving, self-restraint, and self-regulation of emotions. The internalizing scales, entered next, contributed significant variance to self-motivation, self-regulation of emotions, and Total EF, but not to the ADHD-EF index. Finally, and most importantly for our hypotheses, both the significance of change in F values (Table 4) and the standardized coefficients (Table 5) indicated that SCT contributed unique variance to the measurement of self-organization/problem solving and total EF summary score, but not to the other subscales of time management, self-restraint, self-motivation, or the index score. This pattern of results held true whether SCT was entered before or after entry of internalizing symptoms (not shown). When entered last in the model, after SCT, internalizing symptomatology continued to significantly predict selfmotivation and self-regulation; however, it no longer predicted to Total EF, indicating that SCT accounted for more of the variance in Total EF. Inspection of the standardized coefficients (Table 5) indicates that among the internalizing scales, BDI-II and STAI-State have significant predictive power for self-motivation (STAI-State in the negative direction) whereas STAI- Trait has significant predictive power for self-regulation of emotions. Partial correlations were conducted to ascertain with which internalizing variables SCT was most highly correlated. Results revealed significant correlations between SCT and STAI-Trait after controlling for STAI-State and BDI-II (r =.23, p =.026). Furthermore, correlations between SCT and BDI-II and STAI-State were each nonsignificant after controlling for the other internalizing scale, indicating that the primary comorbidity between SCT and internalizing symptoms is with trait anxiety. p

7 Table 3. Zero-Order Correlations (Pearson s r) Between Independent Variables and Subscales. Age ADHD-I ADHD- HI BDI-II STAI- State STAI- Trait SCT Time Organization Restraint Motivation Age 1 ADHD-I ADHD-HI ** 1 BDI-II * STAI-State ** ** 1 STAI-Trait **.225*.696**.793** 1 SCT.247*.310** *.271*.366** 1 Time.271*.280* Organization ** *.259*.276* Restraint **.552** **.273* Motivation * * ** 1 Emotion **.406**.419**.520**.576**.268* **.510** Total EF ** **.258*.396**.339**.507**.587**.405**.367**.589** 1 ADHD index **.256*.219*.351**.355** ** ** **.377** 1 Emotion Total EF ADHD index Note. Sample size for all correlations is 82 (complete cases). Internalizing scales includes BDI-II, STAI-State, and STAI-Trait. = Barkley Deficits in Executive Functioning Scale; ADHD-I = Conners Adult ADHD Rating Scale Self-Report Long Form Subscale E, DSM-IV Inattentive Symptoms; ADHD-HI = Conners Adult ADHD Rating Scale Self-Report Long Form Subscale F: DSM-IV Hyperactive/Impulsive Symptoms; BDI-II = Beck Depression Inventory II; STAI = State-Trait Anxiety Inventory; SCT = sluggish cognitive tempo; time = Self-Management to Time; organization = Self-Organization/Problem-Solving; emotion = Emotional Self-Regulation; EF = executive function. *p <.05. **p <.01. NP6

8 Table 4. Hierarchical Multiple Regression Models Predicting Subscale Scores From Age, ADHD Symptoms, Internalizing Symptoms, and SCT. subscale Predictor Self-Management to Time Self-Organization/Problem Solving Self-Restraint Self-Motivation Self-Regulation of Emotions Total EF ADHD index Age R ΔF 6.33* df(1,2) 1,84 1,84 1,84 1,84 1,84 1,84 1,80 ADHD-I R ΔF 5.89* 11.30** 15.22*** 5.59* 10.30** 12.07** 9.43** df(1,2) 1,83 1,83 1,83 1,83 1,83 1,83 1,79 ADHD-HI R ΔF * 29.05*** ** df(1,2) 1,82 1,82 1,82 1,82 1,82 1,82 2,78 Internalizing Scales R ΔF * 9.66*** 2.87* 1.88 df(1,2) 3,79 3,79 3,79 3,79 3,79 3,79 3,75 SCT R ΔF * * 0.57 df(1,2) 1,78 1,78 1,78 1,78 1,78 1,78 1,74 Note. Sample size for all analyses is 86 except for ADHD-EF index, for which sample size is 82. Internalizing scales are the Beck Depression Inventory-II and State-Trait Anxiety Inventory. = Barkley Deficits in Executive Functioning Scale; DSM-IV = Diagnostic and Statistical Manual of Mental Disorders, 4th edition; BDI-II = Beck Depression Inventory II; STAI = State-Trait Anxiety Inventory; SCT = sluggish cognitive tempo; EF = executive function; ADHD-I = Conners Adult ADHD Rating Scale Self-Report Long Form Subscale E, DSM-IV Inattentive Symptoms; ADHD-HI = Conners Adult ADHD Rating Scale Self-Report Long Form Subscale F: DSM-IV Hyperactive/Impulsive Symptoms. *p <.05. **p <.01. ***p <.001. NP7

9 Table 5. Standardized Beta Values for Variables in Full Hierarchical Regression Model Predicting Subscale Scores From Age, ADHD Symptoms, Internalizing Symptoms, and SCT. Predictor subscale Self-Management to Time Self-Organization/Problem Solving Self-Restraint Self-Motivation Self-Regulation of Emotions Total EF Summary Score ADHD-EF index Age.24* ADHD-I.27*.33**.20.28* ADHD-HI.14.26*.50***.06.29** BDI-II ** STAI-State * STAI-Trait * SCT Total.09.29* *.09 Total R Note. Sample size for all analyses is 86 except for ADHD-EF index, for which sample size is 82. = Barkley Deficits in Executive Functioning Scale; SCT = sluggish cognitive tempo; EF = executive function; ADHD-I = Conners Adult ADHD Rating Scale Self-Report Long Form Subscale E, DSM-IV Inattentive Symptoms; ADHD-HI = Conners Adult ADHD Rating Scale Self-Report Long Form Subscale F: DSM-IV Hyperactive/Impulsive Symptoms; BDI-II = Beck Depression Inventory II; STAI = State-Trait Anxiety Inventory; DSM-IV = Diagnostic and Statistical Manual of Mental Disorders, 4th edition. p <.10. *p <.05. **p <.01. ***p <.001. NP8

10 Leikauf and Solanto NP9 Discussion The results of this study of SCT in a clinically referred sample of adults with ADHD of a wide age range demonstrate that SCT correlates significantly with ADHD inattentive symptoms, internalizing symptoms, and EF deficits. Our results supported a stronger association between SCT and inattentive symptoms than between SCT and hyperactiveimpulsive symptoms, as has been previously described in children (Frick et al., 1994; Lee et al., 2014). However, as in the previous study of adults, the rates of clinical diagnosis of ADHD-I and ADHD-C did not differ significantly between the high SCT and low SCT groups (Barkley, 2012b). Previous studies in children have thus far generally found higher SCT ratings in ADHD-I than ADHD-C (Garner et al., 2010; Willcutt et al., 2014), but not to a degree sufficient to increase accuracy of subtype identification (Harrington & Waldman, 2010). Correlations between SCT and dimensional measures of depression and anxiety were significant, but rates of mood and anxiety disorders did not significantly differ between participants high and low in SCT. This finding extends to adults the connection between SCT and internalizing symptoms previously observed in children (Becker et al., 2014; Capdevila-Brophy et al., 2014; Garner et al., 2010; Garner et al., 2013; Lee et al., 2014; Willcutt et al., 2014). Results of hierarchical regression revealed that DSM-IV Inattentive symptomatology was the only variable that contributed to all EF subscales and was the sole variable that predicted self-management to time. After accounting for inattentive symptoms, DSM-IV Hyperactive/Impulsive symptomatology contributed additional variance to EF subscales related to self-restraint and self-regulation, both of which are associated with poor impulse control. After consideration of ADHD symptoms, internalizing symptoms contributed additional unique variance to self-regulation of emotions and self-motivation. The characteristics measured by self-regulation of emotion and self-motivation on the thus appear to be largely emotionally driven and are more highly associated with internalizing psychopathology than with ADHD-related executive dysfunction. Given our initial specific aims, the most noteworthy finding to emerge from this study is the significant relationship between SCT and executive dysfunction as measured by the Self-Organization/Problem-Solving subscale and the Total EF Summary subscale. Our study replicates the previous findings of a relationship between SCT and deficits in self-organization/problem solving in college students (Jarrett et al., 2014) and the parallel, though weaker, findings in children and adolescents (Barkley, 2013). Organization was also among the EF deficits found to be associated with SCT symptoms by some groups using the BRIEF (Araujo Jiménez et al., 2015; Becker & Langberg, 2014). Importantly, the current study demonstrates the predictive utility of SCT vis-à-vis these indices of executive dysfunction over and above correlations between SCT and ADHD or internalizing symptoms. The beta coefficients from the hierarchical regression models also indicate that specific internalizing symptoms had specific associations with different subscales. Namely, BDI-II and STAI-State were predictive of self-motivation (STAI-State in the negative direction) and STAI-Trait of self-regulation of emotions. It is interesting in this context that among the internalizing variables, SCT was primarily correlated with trait anxiety, rather than with depression or with state anxiety. These findings were not directly related to our hypotheses regarding SCT, but nevertheless contribute to a better characterization of specific relationships between subscales and non-adhd Symptom scales. In summary, the current study adds to a growing body of evidence that SCT contributes additional impairment in EF that is not accounted for by comorbid ADHD or internalizing symptoms and that this impairment is primarily in the domain of organization and problem solving. This finding may help to explain the functional impairment in work and education associated with SCT in adults (Barkley, 2012b) as well as the report of a negative association between SCT and quality of life in adults (Combs, 2014). Furthermore, it is consistent with our finding in this sample of lower educational attainment in adults with high SCT. This finding needs further replication before firm conclusions can be made regarding any specific relationship between SCT symptoms and educational attainment in adults with ADHD. Overall, these results demonstrate that SCT in adults is not exclusively a proxy for ADHD symptom severity or internalizing symptomatology. Rather, SCT symptoms predict independent executive functioning impairment above and beyond that predicted by ADHD and internalizing symptoms. Limitations of this study include the fact that structured diagnostic interviews were not used to establish diagnoses and that symptoms were measured by self-report. However, the use of CAARS-E symptoms as an inclusion criterion adds validity to the clinical diagnoses. In addition, the results found for this well-educated, treatment-seeking sample may not be fully generalizable to the entire population of adults with ADHD. Conclusions also cannot be generalized to persons without ADHD. Authors Note John E. Leikauf is now at the Department of Psychiatry and Behavioral Sciences, Stanford University. Mary V. Solanto is now at the Department of Psychiatry, New York University School of Medicine. Acknowledgments The authors thank Eva Petkova, PhD, of the Department of Child and Adolescent Psychiatry, New York University School of Medicine, for biostatistical consultation

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