Emotional and behavioural problems in young children with autism spectrum disorder

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1 DEVELOPMENTAL MEDICINE & CHILD NEUROLOGY ORIGINAL ARTICLE Emotional and behavioural problems in young children with autism spectrum disorder SUSIE CHANDLER 1,2 PATRICIA HOWLIN 2,3 EMILY SIMONOFF 2,4 TONY O SULLIVAN 5 EVELIN TSENG 6 JULIET KENNEDY 7 TONY CHARMAN 2 GILLIAN BAIRD 1 1 Paediatric Neurosciences, Newcomen Centre, Guy s & St Thomas NHS Foundation Trust, King s Health Partners, London; 2 Institute of Psychiatry, Psychology & Neuroscience, King s College London, London, UK. 3 Faculty of Health Sciences, University of Sydney, Sydney, NSW, Australia. 4 National Institute for Health Research (NIHR) Biomedical Research Centre for Mental Health, Institute of Psychiatry, Psychology & Neuroscience, King s College London, London; 5 Kaleidoscope Lewisham Centre for Children and Young People, Lewisham & Greenwich NHS Trust, London; 6 Bromley Healthcare CIC Ltd, London; 7 The Nuffield Orthopaedic Centre, Oxford University Hospitals NHS Trust, Oxford, UK. Correspondence to Gillian Baird at Children s Neurosciences Centre, Block D, St Thomas Hospital, Westminster Bridge Road, London SE1 7EH, UK. gillian.baird@gstt.nhs.uk This article is commented on by Smith on pages of this issue. PUBLICATION DATA Accepted for publication 18th May Published online 16th June ABBREVIATIONS ASD Autism spectrum disorder DBC Developmental Behaviour Checklist DBC-P Developmental Behaviour Checklist Primary Carer Version DBC-T Developmental Behaviour Checklist Teacher Version SCQ Social Communication Questionnaire AIM To assess the frequency, pervasiveness, associated features, and persistence of emotional and behavioural problems in a community sample of young children with autism spectrum disorder (ASD). METHOD Parents (n=277) and teachers (n=228) of 4- to 8-year-olds completed the Developmental Behaviour Checklist (DBC). Intellectual ability and autism symptomatology were also assessed. A subsample repeated the DBC. RESULTS Three-quarters of the cohort scored above the clinical cut-off on the Developmental Behaviour Checklist Primary Carer Version (DBC-P) questionnaire; almost two-thirds of these scored above cut-off on the Developmental Behaviour Checklist Teacher Version (DBC-T) questionnaire. In 81%, problems persisted above threshold 14 months later. Higher DBC-P scores were associated with greater autism symptomatology, higher deprivation index, parental unemployment, and more children in the home but not with parental education or ethnicity, or child s age or sex. Children with IQ>70 scored higher for disruptive behaviour, depression, and anxiety symptoms; those with IQ<70 scored higher for self-absorption and hyperactivity. INTERPRETATION The DBC identifies a range of additional behaviour problems that are common in ASD and which could be the focus for specific intervention. The results highlight the potential benefit of systematic screening for co-existing problems. Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by impairments in reciprocal social interaction, communication, and repetitive, stereotyped interests and behaviours. 1 Recent estimates suggest a prevalence rate of over 1%. 2 ASD is associated with high comorbidity and significant costs to individuals, families, and services. 3 Emotional and behavioural problems in ASD are frequent, 4 and rates of social anxiety, attentiondeficit hyperactivity disorder and oppositional disorder are elevated compared both with the general population 5 and with children with intellectual disability. 6 8 Functional problems in sleeping, eating, and toileting are also increased. High rates of behavioural and emotional disturbance are evident from pre-school onwards 9 and many children have two or more comorbid problems. 10,11 In non-asd populations with and without intellectual disability, prevalence and types of emotional and behavioural difficulties are associated with age, sex, IQ, ethnic group, and social disadvantage. 5,7 In ASD these factors are less clearly linked to psychiatric co-morbidity 6,11 although the type of difficulty does vary with IQ, age, and sex. 6 Psychiatric disorders also have a high prevalence in adults 12 and, together with functional problems, can have as great an adverse impact as core ASD symptoms. There is, nevertheless, a range of evidence-based interventions that could reduce the effects of these problems. 13 Hence systematic assessment of emotional/behavioural difficulties by clinicians is crucial. This paper describes the use of parent and teacher questionnaires to assess comorbid emotional and behavioural problems in a community sample of young children (age 4 9y) with ASD. METHOD The study was approved by Guy s Hospital Research Ethics Committee (08/H0804/37) and Bromley and Lewisham Local Research Ethics Committees (RDLEWBR 428). Recruitment procedures The target population comprised all children born between 1 September 2000 and 1 September 2004 (aged 4 8y at 202 DOI: /dmcn Mac Keith Press

2 time of recruitment) with a diagnosis of ASD made by the local multidisciplinary teams and living in two London boroughs with a broad range of socio-economic circumstances and ethnic backgrounds. In both boroughs, children suspected of having ASD receive a neurodevelopmental assessment from the community paediatrician. A few are diagnosed at this appointment but most are referred onto the multidisciplinary communication clinic. After a speech and language assessment and report from nursery/school, children then attend the multidisciplinary clinic consisting of a paediatrician, a speech and language therapist, or psychologist for a formal assessment of features specific to ASD. Measures include the Autism Diagnostic Interview-Revised, 14 Developmental, Diagnostic and Dimensional Interview, 15 Diagnostic Interview for Social Communication Disorder, 16 or local pro forma and the Autism Diagnostic Observation Schedule. 17 Eligible families (n=447) were mailed invitations to participate together with consent forms. Consenting families were mailed the questionnaire pack. Non-responders were telephoned and r ed. If they still failed to respond, researchers telephoned again and offered to r the questionnaires or complete them with parents over the telephone or at home. To assess pervasiveness of problems, teachers were asked to complete the teacher version of the questionnaire. To assess the persistence of difficulties a subset of parents completed the questionnaire on two occasions (times 1 and 2). For the assessment at time 2, females were over-sampled to provide adequate numbers for analysis (further details in Appendix S1, online supporting information). Measures Emotional and behaviour problems A focus group of eight parents with children with ASD aged younger than 10 years was recruited to determine which of several questionnaires, commonly used in clinical practice in the UK, best described their child s emotional and/or behavioural problems and was most acceptable to them (details in Appendix S2, online supporting information). The Developmental Behaviour Checklist (DBC 18 ) was selected as the preferred instrument for the study. Parents rated it positively in terms of acceptability, ease of use, clarity of questions, scoring, and range of questions, and there are parallel parent and teacher versions that allow assessment of problems across settings. The DBC Primary Carer Version (DBC-P) is a 96-item behaviour checklist covering a broad range of behaviours, each rated as 0 ( not true as far as I know ), 1 ( somewhat or sometimes true ), or 2 ( very or often true ). It has satisfactory internal consistency, interrater and test retest reliability, and concurrent validity with other psychopathology measures, particularly in samples of children and adolescents with intellectual disability. 19,20 The DBC has five empirically derived subscales (Disruptive/Antisocial; Selfabsorbed; Communication Disturbance; Anxiety; Socialrelating), and four scales that can be used to identify What this paper adds Three-quarters of 4- to 8-year-olds with autism have parent-reported emotional and behavioural problems. Two-thirds of these also have teacher-reported problems. Problems persist over time in 80%, and identification is possible at 4 to 5 years. The Developmental Behaviour Checklist assesses a wide range of difficulties in children with autism spectrum disorder (ASD). Systematic use of such a questionnaire is recommended in routine clinical care of children with ASD. specific psychiatric syndromes (Autism Screening Algorithm; Depression scale; Hyperactivity scale, and Anxious Behaviour Rating Scale). The total behaviour problem score (range 0 192) indicates overall level of disturbance; a cut-off score of at least 46 is recommended for identifying clinically significant emotional and/or behavioural problems. The DBC Teacher Version (DBC-T) has 94 items; a total score of at least 30 is recommended as the cut-off for identifying caseness. Autism symptomatology Autism symptomatology was measured using the parentrated Social Communication Questionnaire Lifetime version (SCQ). 21 It comprises 39 items scored 0 or 1; a cut-off of more than 15 is recommended for identifying potential cases of ASD. Demographic characteristics Demographic characteristics were collected by means of a parent questionnaire. Postcode data were used to access a deprivation index (The English Indices of Deprivation 2007), 22 which ranks small geographical areas across England according to deprivation level, based on income, education, employment, and living environment (a higher index score means greater deprivation). Child assessments IQ was measured by the research team, trained and experienced in psychometric assessments, using either the Wechsler Intelligence Scale for Children, 23 Wechsler Preschool and Primary Scale of Intelligence, 24 or Mullen Scales of Early Learning 25 depending on chronological age and developmental level (Appendix S2). Parents were also asked, At what age do you think your child is functioning overall?. The British Picture Vocabulary Scale 26 was used to measure receptive language for children who had sufficient language to access the test. Data analysis Statistical analyses used STATA 11 (StatCorp, College Station, TX, USA, 2009). For some analyses IQ was treated as continuous and for others as a dichotomous variable (<70/>70). For sleeping, eating, and toileting problems, the somewhat / sometimes and very often / often categories of the DBC were combined to create a dichotomous score. Associations between DBC-P/T scores and background factors (number of children at home; parent education, Emotional and Behavioural Problems in ASD Susie Chandler et al. 203

3 employment, and ethnicity) were examined using multiple linear regression. Multinomial logistic regression was used to explore factors associated with discrepancies (i.e. above/ below clinical cut-off) between primary carer (hereafter referred to as parent) and teacher questionnaires, and to explore factors associated with changes in parent questionnaires (i.e. above/below clinical cut off) at times 1 and 2 (see Appendix S1 for full details). RESULTS Participant characteristics Responses were received from 362 of 447 (81%) families (see Figure S1, online supporting information). Parental questionnaires were completed on 277 children (62%), half by post, the remainder by telephone or home visit. Nonparticipating families had a higher mean deprivation index (t[443])=3.39, p<0.001) and contained a higher proportion of males (v 2 [1, n=447]=5.36, p=0.021) (see Appendix S3, online supporting information, for details of participants and non-participants at initial assessment). Mean age of child participants at recruitment was 6 years (SD 1y 1mo) and at first assessment 6 years 10 months (SD 1y 2mo). Most (77%, n=214) attended mainstream school; 44 attended special schools; 15 attended special units within mainstream schools; three were home-schooled; one attended mainstream nursery. The clinical records of any child with a low score on the SCQ score (i.e. total <10; n=28) were checked with local clinicians; diagnosis was confirmed in all cases and none was excluded from the sample. Cognitive assessments were completed for 258 children. Full-scale IQ scores were calculated for 211 (67 on the Wechsler Intelligence Scale for Children; on the Wechsler Preschool and Primary Scale of Intelligence 24 ). For children tested on the Mullen Scales of Early Learning, 25 the composite standard score was used when possible (n=13); for those above the Mullen Scales of Early Learning age range (n=34), age-equivalents were used to derive a ratio IQ. Those with a Mullen Scales of Early Learning ratio IQ<20 (n=11) were assigned an IQ of 19 to reflect their very low ability. Parental estimates of functional age were also used to generate a parent-estimated developmental quotient for 15 children (details in Appendix S4, online supporting information). The mean IQ estimate for the sample was 72.7; 35% had an IQ<70; 21.6% had an IQ<50. Missing cognitive data were because of lack of parental consent or child compliance issues. DBC-P scores are presented in Table I. The internal consistency of each of the subscales (Disruptive/Antisocial, Self-absorbed, Communication Disturbance, Anxiety, Social Relating), the Autism Screening Algorithm, Depression and Hyperactivity scales, and Anxious Behaviour Table I: Mean DBC-P and DBC-T scores by IQ group and sex IQ<70 (n=96) IQ 70 a (n=177) Males (n=227) Females (n=50) Total sample (n=277) Mean scores (SD) DBC-P Total behaviour problem score 72.3 (24.8) 70.2 (32.1) 71.6 (30.4) 69.1 (25.6) 71.2 (29.6) Disruptive/Antisocial 19.5 (9.1) b 23.2 (11.4) b 22.1 (11.0) 21.5 (10.0) 22.0 (10.8) Self-absorbed 27.4 (11.5) c 19.9 (11.5) c 22.8 (12.2) 21.8 (11.4) 22.6 (12.0) Communication disturbance 10.6 (4.7) 11.1 (5.1) 11.2 (5.1) 10 (4.6) 11.0 (5.0) Anxiety 7.2 (3.5) 8.2 (4.5) 7.8 (4.2) 8.0 (4.0) 7.8 (4.2) Social relating 6.7 (2.8) 6.0 (3.3) 6.3 (3.3) 6.1 (2.9) 6.3 (3.2) Autism screening algorithm 31.0 (9.8) c 25.8 (11.4) c 28.1 (11.3) 26.5 (10.4) 27.8 (11.1) Depression scale 5.2 (3.1) b 6.4 (3.8) b 6.0 (3.7) 6.1 (3.0) 6.0 (3.6) Hyperactivity scale 8.3 (2.8) b 7.4 (3.3) b 7.8 (3.2) 7.3 (2.8) 7.7 (3.1) Anxious Behaviour Rating Scale 5.1 (3.1) b 6.3 (3.6) b 5.9 (3.5) 5.9 (3.6) 5.9 (3.5) Sleeps too little/disrupted sleep (%) Has nightmares/night terrors/sleepwalks (%) 27.1 b 45.5 b Fussy eater/has food fads (%) Gorges on food (%) 31.3 b 18.6 b Urinates outside the toilet (%) Soils outside the toilet/smears (%) 39.6 c 15.8 c DBC-T Total behaviour problem score 45.7 (18.4) c 34.0 (21.4) c 38.6 (20.2) 36.2 (24.6) 38.1 (21.1) Disruptive/Antisocial 11.8 (7.2) 11.3 (8.9) 11.5 (8.4) 11.1 (8.4) 11.4 (8.3) Self-absorbed 17.3 (8.9) c 9.0 (7.5) c 12.1 (8.4) 11.3 (10.8) 12.0 (8.9) Communication disturbance 6.7 (3.9) c 4.5 (3.7) c 5.5 (3.9) 4.5 (4.1) 5.3 (3.9) Anxiety 3.8 (2.5) 3.2 (2.7) 3.3 (2.6) 4.0 (2.8) 3.4 (2.6) Social relating 5.9 (3.3) b 4.4 (3.3) b 5.0 (3.4) 4.3 (3.4) 4.9 (3.4) Autism screening algorithm 20.7 (9.0) c 12.6 (8.9) c 15.7 (9.2) 14.6 (11.8) 15.5 (9.8) Depression scale 2.9 (2.2) 3.1 (2.5) 2.9 (2.4) 3.6 (2.5) 3.0 (2.4) Hyperactivity scale 6.0 (3.1) c 4.5 (3.4) c 5.2 (3.3) 4.2 (3.4) 5.0 (3.4) Anxious Behaviour Rating Scale 2.7 (2.3) 2.8 (2.5) 2.7 (2.3) 3.3 (2.6) 2.8 (2.4) a Total n with IQ data=273 (four cases missing IQ data). b Student s t-test (means comparison) or v 2 (% comparison), p<0.05. c Student s t-test (means comparison) or v 2 (% comparison), p< DBC-P, Developmental Behaviour Checklist Primary Carer Version; DBC-T, Developmental Behaviour Checklist Teacher Version. 204 Developmental Medicine & Child Neurology 2016, 58:

4 Rating Scale was good to excellent (Chronbach s a range , mean 0.80). Mean total behaviour problem score was 71.2 (SD 29.6); 79% scored above cut-off (95% at age 4; 83% at age 5; 76% at age 6; 75% at age 7; 80% at age 8), significantly higher than the 41% who scored above cut-off in the Australian normative intellectual disability sample aged 4 to 8 years (Skuse et al. 15 )(p<0.001). There was no significant difference in total problems scores for children with IQ above or below 70 (t[271]= 0.56, p=0.58) but there were some group differences in subscale scores. Thus, children with IQ>70 scored higher on the scales for Disruptive/Antisocial behaviour (t[271]= 2.70, p=0.007), Depression (t[271]= 2.55, p=0.012), and Anxious behaviour (t[271]=2.30, p=0.004). Children with IQ<70 scored more highly on the Self-absorbed (t[271]= 2.70, p<0.001) and Hyperactivity scales (t[271]=2.30, p=0.022). Seventy per cent of the sample were reported to be fussy eaters/have food fads; disrupted sleep was reported in 59% and soiling/smearing in 24%. Soiling/smearing was more common in younger children (i.e. <7y vs >7y, v 2 =3.84, p=0.050); no other sleeping/eating/toileting problems were associated with age (all p>0.2). No significant sex differences were found between total or subscale scores (all p>0.3). There was no correlation between total DBC-P score and age, IQ, British Picture Vocabulary Scale standard score, or sex (all correlations <0.10; see Table II). However, there was a significant correlation with greater autism symptoms on the SCQ (r=0.58; p<0.001), and with higher deprivation index score (although the correlation was small; r=0.15; p=0.01). Multiple regression also showed DBC-P score to be associated with parental unemployment (b= p=0.008) and more children in the home (b=5.94, p=0.008). There was no association between DBC-P score and parental education (p=0.48) or ethnicity (p=0.14). Almost half (44%) the parents indicated that they had sought help for their child s behaviour or emotional problems. Most (86%) of those who had sought help had children who scored above the DBC-P clinical cut-off. However, over one-third (37%) of those whose children scored above cut-off had not sought any help. Teacher reports of emotional and behaviour problems DBC-T data were available for 228 of the children with parent data (see Table I). Missing data were largely due to teachers not returning the questionnaire. Children lacking teacher data were slightly older than those with teacher data (mean 7y 1mo, SD 1y 1mo and mean 6y 8mo, SD 1.2 respectively, t[275]=2.1, p=0.04), but they did not differ in terms of SCQ score (p=0.76) or sex (p=0.12). Mean total score on the DBC-T was 38.1 (SD 21.1); 62% scored above the cut-off for major emotional and/or behavioural disturbance. Mean total and subscale scores for this ASD sample were significantly higher than those for the normative intellectual disability sample 15 (p<0.05 in Table II: DBC-P and DBC-T total scores: Pearsons correlations with age, IQ, SCQ, deprivation index, and regression analysis for effect of background factors n r value p value DBC-P total score with: BPVS standard score Child s age SCQ total score < DBC-T total score Deprivation index DBC-T total score with: IQ < BPVS standard score Child s age SCQ total score Deprivation index DBC-P total score (n=250) Coefficient (SE) t p value Parent education 3.03 (3.80) Parent employment (4.30) Ethnicity (3.79) Number of children 6.42 (2.25) DBC-T total score (n=205) Parent education 2.47 (2.96) Parent employment 1.15 (3.30) Ethnicity 1.54 (2.91) Number of children 5.40 (1.75) DBC-P, Developmental Behaviour Checklist Primary Carer Version; DBC-T, Developmental Behaviour Checklist Teacher Version; SCQ, Social Communication Questionnaire; BPVS, British Picture Vocabulary Scale. each case). Teachers rated children with IQ<70 as being more self-absorbed (t[226]=7.48 p<0.001), and having more problems with communication (t[226]=4.22, p<0.001) and social-relating (t[226]=3.2, p=0.002) than those with IQ>70 (see Table I). There was no significant relationship between IQ and DBC-T Disruptive/Antisocial or Anxiety subscale scores (p=0.67 and 0.08 respectively). No sex differences were found on DBC-T subscale scores (Student s t-tests, all p>0.1). Unlike the parent ratings, total DBC-T score was negatively correlated with IQ (r= 0.34; p<0.001) and British Picture Vocabulary Scale standard scores (r= 0.23; p=0.002) although these correlations were weak to moderate (see Table II). There was no correlation between DBC-T scores and autism severity (SCQ; r=0.06; p=0.33). Multiple linear regression showed higher DBC-T scores were associated with greater family size/more children (F 4,200 =2.75, p=0.03, b= 5.38, p=0.002) but not with any other family factors or school placement. Agreement between parent and teacher reports Two-thirds (64%) of children above clinical cut-off on the DBC-P were also above the cut-off on the DBC-T, indicating that significantly more parents than teachers rated children as having emotional/behavioural problems (onesample proportion test, z[n=228]= 6.2, p<0.001). There was no significant correlation between DBC-P and DBC-T total scores (r=0.07, p=0.29). The discrepancy between caseness (reaching cut-off) on the DBC-P and the DBC-T was examined using multinomial regression for Emotional and Behavioural Problems in ASD Susie Chandler et al. 205

5 Table III: Developmental Behaviour Checklist Primary Carer Version scores at times 1 and 2 (n=93) Mean score (SD), time 1 Mean score (SD), time 2 r value Total behaviour 71.8 (27.5) b 59.4 (2.6) b 0.79 c problem score Disruptive/Antisocial 21.8 (10.3) b 17.8 (9.6) b 0.79 c Self-absorbed 23.5 (12.2) b 19.2 (10.8) b 0.78 c Communication 10.7 (4.7) b 9.1 (2.8) b 0.66 c Disturbance Anxiety 8.1 (3.9) b 6.6 (3.4) b 0.75 c Social Relating 6.3 (3.0) a 5.6 (2.8) a 0.51 c Autism Screening 28.0 (10.6) b 24.0 (10.5) b 0.78 c Algorithm Depression scale 6.0 (3.4) b 4.7 (2.9) b 0.78 c Hyperactivity scale 7.7 (3.1) b 6.8 (3.2) b 0.70 c Anxious Behaviour Rating Scale 6.0 (3.3) b 5.2 (3.1) b 0.77 c a Paired Student s t-test, p<0.05. b Paired Student s t-test, p< c Pairwise correlation, p< each of the four possible concordance/discordance categories (see Appendix S1 for details). Being above cut-off on the DBC-P but not the DBC-T, relative to being above cut-off on both, was associated with living in a home with more children (Wald[1]=17.4, p<0.001), higher IQ (Wald [1]=11.4, p<0.005), and female sex (Wald[1]=9.4, p<0.005). Persistence of emotional and behavioural problems over time Ninety-three families repeated the DBC-P after an average interval of 14 months (SD 4.6; range 2 23). They did not differ from the other 184 in terms of age or deprivation index (Student s t-tests, p=0.12 and 0.17 respectively) but they had a slightly lower mean IQ (67.6 vs 75.3, p=0.02) and differed, by design, in the percentage of males (57% vs 77%, v 2 =58.9, p<0.001) because females were deliberately oversampled to obtain sufficient numbers for analysis of sex. There was a reduction in total and subgroup scores from time 1 to time 2 (see Table III) but 81% of those above cut-off initially remained above cut-off at time 2. Scores at time 1 and time 2 were highly correlated (r[93] =0.79 p<0.001). Three children below cut-off at time 1 scored above cut-off at time 2; 14 children were above cutoff at time 1 but not time 2. Multinomial regression analysis on time 1/time 2 concordance (see Appendix S1) indicated that scoring above DBC-P cut-off at time 1 but not time 2 relative to those scoring above cut-off at both timepoints was associated with lower SCQ total (Wald[1]=6.12, p=0.013). No family variables (including whether or not parents reported seeking help for the problems at time 1) were related to change over time (i.e. DBC-P at time 1, DBC-P at time 2). DISCUSSION As in previous research, 6,11 the present study identified high levels of emotional and behavioural problems in young children with ASD. Three-quarters scored above clinical cut-off on the DBC-P. High rates of functional problems were also reported compared with children of similar age; for example disrupted sleep in 59%, 70% fussy eaters, and 24% and 34% respectively having soiling and urinating problems (despite being toilet-trained). Two-thirds of children with ASD who were above the DBC-P cut-off were also above cut-off on the teacher report, indicating pervasiveness of problems. Problems were persistent. Most children (81%) initially above cut-off remained above cut-off after an average period of 14 months, although total problem scores reduced somewhat over time, consistent with previous studies. 27,28 Nevertheless, less than half the parents/carers of these children had sought help for these difficulties. The lack of association between overall rate of parentreported emotional and behaviour problems and child factors (i.e. sex, IQ, language, age) is consistent with the literature in ASD 6,11 and different from both general population samples and clinical groups with and without intellectual disability. 5,7 However, in contrast to Simonoff et al., 11 severity of ASD in this study was associated with parental report of problems (although not teacher report). Possible explanations are differences in age of the participants and the measures used. Consistent with studies of the general population 5 and of intellectual disability 7 and some studies of ASD, 29 although not all, 11 psychosocial factors (higher deprivation, parental unemployment, and number of children in the home, but not parental education or ethnicity) were associated with higher parental ratings of emotional and behaviour problems. Also consistent with other studies, type of symptoms varied with IQ. Children with IQ<70 were more self-absorbed than others, 6 and children with IQ>70 scored more highly for depression, anxiety, 30 and attention-deficit hyperactivity disorder. 30 Higher DBC-T scores were associated with greater family size but no other family factors. Discrepancy between parental and teacher reports of overall problem severity (DBC-P>DBC-T) tended to be related to female sex, higher IQ, and larger family size. It is possible that children with higher IQ respond positively to the structure and expectations of school; alternatively, they may contain or suppress any anxiety or distress they experience in school and thus behave differently at home and in school. Different behaviour across home and school situations is well recognized in child psychopathology and there is anecdotal evidence that females with ASD may be more concerned to conform in school; therefore, parent experience is of greater behaviour problems. Type of school was not associated with either parent or teacher reports. The strengths of this study include a large, total-population-derived cohort (although non-participants included more males and had higher deprivation index, thus possibly underestimating total problems); young age of the children; standardized IQ scores available for almost all; data collected from both parents and teachers; and follow-up measures obtained for a subgroup of children. Limitations include no confirmation of clinical diagnoses using a 206 Developmental Medicine & Child Neurology 2016, 58:

6 research diagnostic assessment (although the SCQ was used); the small number of females available to assess possible sex differences; lack of an adaptive behaviour measure; and reliance on checklist data rather than clinician validation of symptoms. Furthermore, the DBC was developed for use with children with intellectual disability. Our sample included children across the full IQ range, indeed 65% had an IQ<70. Although it is possible that the DBC may not have been sensitive enough to detect all problems in children with higher IQs, we found no relationship between IQ and overall problem levels, and the variation in patterns of problems according to IQ was consistent with other studies. Autism is currently being diagnosed at ever-younger ages. 31 Our findings, alongside those of others, show that significant comorbid emotional and behaviour problems can be detected as early as age 4 to 5 years. These difficulties occur both at home and at school and persist over time. The identification of comorbid problems is important for parents and crucial in the management of ASD as the impact of these additional problems can be reduced using a range of evidence-based interventions. 13 Consistent with UK National Institute for Health and Care Excellence guidance, 13 systematic eliciting of co-occurring problems by clinicians as part of routine assessment and care in ASD is recommended. Although several behaviour measures exist, parents of children across the IQ range found the DBC easy to use and understand, and it covers a range of behaviours including sleeping, eating, and toileting problems. The availability of both Primary Carer and Teacher Versions increases its value for measuring problems in different settings. ACKNOWLEDGEMENTS We thank Lewisham Autism Support and the Complex Communication Diagnostic Service in Bromley for their support. We thank all the families and schools who participated. This paper represents independent research part funded by the National Institute for Health Research (NIHR) Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King s College London and Research Autism. The views expressed are those of the authors and not necessarily those of the National Health Service, the National Institute for Health Research, or the Department of Health. Funding source: Clothworkers Foundation, brokered by Research Autism. Grant number: R Autism M /12. The authors have stated that they had no interests that might be perceived as posing a conflict or bias. SUPPORTING INFORMATION The following additional material may be found online: Figure S1: The target population and response rate. Appendix S1: Data analysis. Appendix S2: Focus group procedure and questionnaire selection. Appendix S3: Sample characteristics and differences between participating and non-participating families. 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