1. Methods for testing trends in mental health – is it really possible to compare ‘like with like’? Dr Stephan Collishaw Cardiff University collishaws@cardiff.ac.uk NCRM Research Methods Festival, Oxford, July 2014

2. Outline Prevalence and burden Trends in diagnosis – need for epidemiological data Cross-cohort comparisons using symptom screens Issues to think about in comparing ‘like with like’ Results – adolescent mental health 1970s-2000s Replication and validation Trends in child mental health 1999-2008

3.  1 in 10 has a clinically significant psychiatric disorder  Impact on family life, friendships, learning  Suicide and self harm (3 rd leading cause of death)  Long-term prognosis  Most child/adolescent disorders persist to adulthood  >50% of adult mental disorders have onset <18 years  Parenting, employment, social exclusion, illness, mortality  Economic burden Child psychiatric disorders: Burden and prognosis Green et al., 2005; Kim-Cohen et al, 2003; Thapar et al., 2012; Windfuhr et al., 2008; Maughan et al., 2014

4. Diagnosis and treatment: autism, ADHD, depression, anxiety Increased help seeking, diagnosis and treatment Substantial increases in psychotropic medication Rates increased 3-5 fold per decade 1990s and 2000s Similar trends in many countries Getahun et al., 2013; Kosidou et al, 2010; Olfson et al., 2014; Stephenson et al, 2013

5. Trends in diagnosis and treatment Important for planning service provision But: Increases in referrals and diagnoses may be due to Increased public awareness & clinical recognition Changing diagnostic criteria and practice Treatment availability and perceived efficacy ‘Medicalisation’ of normal behaviour? Also: Majority still don’t access services Ford et al., 2007; Potter et al., 2012

6. Epidemiological evidence  Two major meta-analyses of depression and ADHD  Epidemiological studies using structured diagnostic interviews  Meta-analyses: no evidence of increase in depression or ADHD But  Variability in methods (samples, measures, diagnostic system)  Rates of depression range from 25%  ‘Noise’ and variability likely to make trends difficult to detect Costello et al., 2006; Polanczyk et al., 2014

7. ‘Like-for-like’ cross-cohort comparisons  Comparable representative cohorts with equivalent measures  e.g. UK cohorts since 1960s have included Rutter/SDQ  Threats to comparability  Selective attrition  Minor changes to questionnaire make a big difference  Disobedience: “applies somewhat” (33%) vs “sometimes” (75%)  Calibration can be effective for aligning non-identical instruments  Change in reporting Goodman et al., 2007

8. UK cross-cohort comparisons: 1974-1999 Collishaw et al, 2004 Large nationally representative surveys (NCDS, BCS70, BCAMHS) assessed in 1974, 1986, 1999 Age 15-16 Parent rated Rutter or SDQ Emotional problems Conduct problems Hyperactivity/inattention Calibration data used to align SDQ and Rutter questionnaires Study-specific weights using prior predictors of non-response

9. Emotional problems: high scores Cohort 3 vs. cohort 2 OR = 1.72 Collishaw et al, 2004 N = 10,499N = 868N = 7,293

10. Conduct problems: high scores Total OR = 1.56 per cohort Collishaw et al, 2004

11. Hyperactivity: mean scores Collishaw et al, 2004

12. Limitations Only parent reports Imperfection of Rutter/SDQ calibration? Crude measures Are population shifts also occurring at extremes? What about ‘change in reporting’? Need for replication and validation

13. Replication: The Youth Trends study (1986 & 2006) Two nationally representative surveys of English youth  1986: BCS70 age 16 (N = 9,766)  2006: HSE follow-up ages 16-17 (N = 747)  Identical self rated symptom screens (GHQ/Malaise) Questions  Increase in youth-reported symptoms  Variation in trends by severity? Collishaw et al, 2010

14. Adolescent emotional symptoms (youth reports) ES = 0.36; p <.001 ES = 0.13; p =.06 Collishaw et al., 2010

15. Trends by severity Collishaw et al, 2010 cohort differences significant at all thresholds, p<.01; Interaction p <.05

16. General shift in reporting? No change in hyperactivity Collishaw et al, 2010

17. Do trends reflect a change in reporting? Shift in informant ‘thresholds’? (e.g. different expectations about normal behaviour) Greater willingness to report problems than in the past? But Specificity of findings (no increase in hyperactivity) Validation using external criteria desirable…

18. Conduct problems: Age 30 outcomes NCDS & BCS70 cohorts Collishaw et al, 2004

19. Adolescent conduct problems and risk of pervasive adult dysfunction: 4+ adverse outcomes age 30 Collishaw et al, 2004

20.  1999: BCAMHS 7-year olds (n = 1034)  2004: BCAMHS 7-year olds (n = 648)  2008: MCS 7-year collection (n = 13,489)  Parent & teacher SDQ symptoms & impact  Weights used to adjust for attrition and stratified design Child mental health trends: 1999-2008 Sellers et al, in press

21. SDQ total and subscale mean scores all declined  Boys: total score effect size = -0.27  Girls: total score effect size = -0.12  Bigger drop in problem scores for boys than girls (p = 0.027)  Similar conclusions based on parent and teacher reports  Drop in children scoring in abnormal range (11%, 10%, 8%)  But: increase in impact of problems, e.g. classroom learning Child mental health trends: 1999-2008 Sellers et al, in press

22. Conclusions Comparing ‘like-with-like’ essential for testing trends Replication and validation important Long-term change in adolescent mental health Recent data: improvements in child mental health Latest data 2008, what has happened since?

23. Barbara Maughan (KCL) Andrew Pickles (KCL) Robert Goodman (KCL) Anita Thapar (Cardiff) Ruth Sellers (Cardiff) Frances Gardner (Oxford) Jacqueline Scott (Cambridge) Ginny Russell (Exeter) National Centre for Social Research; Department of Health Medical Research Council; Nuffield Foundation; Waterloo Foundation Acknowledgements

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