Growing out of ADHD?
Attention Deficit Hyperactivity Disorder (ADHD), characterised by pervasive inattention, hyperactivity and impulsivity, is one of the most common childhood psychological disorders affecting around 3-5% of all children. Over the last week there have been headlines suggesting that ‘kids may outgrow ADHD‘ and ‘by age 18, most kids ADHD is gone‘ based on a UK research study. Let’s look at the evidence for this and examine this claim in the context of the broader literature.
What did the study involve?
The study was actually focused on sleep quality in children with ADHD rather than the persistence of ADHD symptoms. The key aim of the study was to examine genetic and environmental influences on sleep quality over time in children and adolescents with the disorder. The participants were members of the Environmental Risk (ERisk) Longitudinal Twin Study, which has tracked the development of a birth cohort of 2,232 British children.
The researchers examined ADHD diagnoses at age 7, 10, 12 and 18. From the initial sample, 2,066 were interviewed at age 18. In this sample, 247 participants (12.1%) met criteria for ADHD in childhood. 12.1% is an unusually high proportion to have met criteria for ADHD in childhood. This number is much higher than common reports in the literature based on UK samples. For example, a group of researchers from the University of Exeter Medical School looked at figures including ADHD diagnoses, from the UK Millennium Cohort Study, which is a sample of more than 19,000 children representative of the UK population; 1.4% of parents reported a diagnosis of ADHD in that UK study.
In the recent paper, the researchers reported that 193 children showed ‘remitted ADHD’ – that is they showed ADHD symptoms in childhood but not at a diagnostic level as 18 year olds. In an article on the topic, the lead researcher stated that ‘78% of the children in our study who had ADHD as a child no longer had the disorder when they were 18’. Subtracting the 9.3% (193 children) who are reported as having remitted from the 12.1% reported as having ADHD as children leaves just under 3% which is much more like the figure that is typically reported of ADHD prevalence. There seems to be something different about the childhood sample in comparison to other samples. The sample itself is a twin sample which the authors themselves note may not readily lend to generalising to the typical non-twin population. The sample also included those deemed ‘at risk’ (teenage mothers with twins) who were specifically recruited to the study although the authors note that the overall sample had a socio-economic representation reflecting that nationwide.
In the paper the researchers refer to a group of adults (age 18) who met criteria for ‘adult-onset ADHD’. This was a sizeable group of 112 18-year-olds. ADHD is a developmental disorder that is typically observed from early in childhood so again this sizeable group suggests that the sample is somewhat different to those reported in the general ADHD literature.
Does ADHD resolve over time?
Although this study suggests that a significant proportion of children with ADHD no longer show those symptoms as adults at a diagnostic level, the bulk of research suggests that ADHD persists into adulthood with an estimated 2-4% of adults still presenting symptoms (e.g. NICE, 2008; Polanczyk & Rohde, 2007). It is well established that some symptoms will wane and this is reflected in a change in diagnostic criteria used to diagnose adults with ADHD in the last revision of the common diagnostic manual used (DSM-V). The NHS advice that “the symptoms of ADHD usually improve with age, but many adults who are diagnosed with the condition at a young age continue to experience problems” reflects the conclusions of the bulk of the literature.
Gregory A. M. et al. (2016). ADHD and Sleep Quality: Longitudinal Analyses From Childhood to Early Adulthood in a Twin Cohort.
Journal of Clinical Child & Adolescent Psychology. DOI: 10.1080/15374416.2016.1183499
Russell, G. et al. (2014). Prevalence of Parent-Reported ASD and ADHD in the UK: Findings from the Millennium Cohort Study. Journal of Autism and Developmental Disorders. DOI: 10.1007/s10803-013-1849-0