Attention deficit hyperactivity disorder: 40 years consistent work

Mr Whitely has failed to mention two of our relevant studies. Our 1997 paper, ‘ADHD: A category or a continuum? Genetic analysis of a large-scale twin study’, showed that heritability was robust across definitions of attention deficit hyperactivity disorder (ADHD) as part of a continuum or as a disorder with various symptom cut-offs, suggesting that ADHD was best viewed as the extreme of a behaviour that varies genetically throughout the entire population (Levy et al., 1997). This is similar to anxiety or blood pressure, where appropriate cut-off levels between normality and pathology may vary according to patient circumstances, and current practice. The study was based on Diagnostic and Statistical Diagnostic and Statistical Manual of Mental Disorders–Third Edition (DSM-III) which used a dimensional measure of ADHD and should be repeated for Diagnostic and Statistical Manual of Mental Disorders–Fourth Edition (DSM-IV) subtypes. Nonetheless, use of dimensional measures with cut-off points for pathology is not uncommon, such as for depression and anxiety in psychiatry and blood pressure in medicine, despite the difficulties posed by defining cut-off levels.

More important in the present context is a study reported by Levy and Hobbes in 1982: ‘A 30-month follow-up of hyperactive children’. The study retrospectively followed up 26 children referred for assessment of ADHD, aged 48–92 months (average 72 months) and assessed by clinical diagnosis, maternal and clinician ratings and a Continuous Performance Task and IQ measures. Three ‘hyperactive’ groups were demonstrated: those maintained on medication, those taken off medication by the end of the study and those not medicated. The psychometric and family structure measures showed that the ‘younger hyperactives’ were children with significant verbal or performance IQ discrepancies, that could improve with age, while the ‘older hyperactives’ had a median IQ of 87 and were shown less likely to improve with age. Of those not treated with medication, 75% were from single-parent families. The study suggested important developmental, psychometric, social and family influences on diagnosis and treatment.

In terms of the International Consensus Statement, those who signed it believed there was a consensus at that time. I believe my clinical and research work over 40 years reflects considerable persistence and a consistent approach.

See Debate by Whitely, 2015, 49(6): 497–498.