This narrative review covered studies that followed people with ADHD from childhood into adulthood. Some followed children seen at clinics, such as the Multimodal Treatment Study of ADHD (MTA). Others followed whole populations or birth cohorts. ADHD seems to last more often in clinic samples, the authors say.
How often ADHD lasted varied widely. The lowest rate was 4%, in a US clinical study of referred boys. The highest was 76%, in a UK clinical study of children and teens. In the MTA, one definition gave 1.9%. Another gave 61.4%. The authors link this spread to diagnostic criteria, who was in the sample, age at assessment, and the information source. They say each factor's role is hard to separate statistically.
The review reports that the main predictors of ADHD lasting were severity, co-occurring conduct disorder and major depression, and ADHD treatment. The authors state that the treatment link is confounded by severity. Among children with ADHD, severity and conduct disorder were the most important predictors of poor adult outcomes, though the authors say poor adult outcomes are unquestionable but their childhood predictors are much less clear.
In three population studies, a large share of adult cases began after childhood. In New Zealand it was 87%. In Brazil it was 87.4%. In the UK it was 67.5%. A register study found that people diagnosed at 18 or older had a higher death rate than the general population, with a larger gap than people diagnosed younger.
The numbers Stats and what the terms mean
The statistics behind the plain-language claims above.
- Register study, year not reported: death rate of people diagnosed with ADHD at 18 or older compared with the general population, mortality rate ratio 4.25 (95 % confidence interval 3.05 to 5.78).
- Register study, year not reported: death rate of people diagnosed at 5 or younger compared with the general population, mortality rate ratio 1.86.
- Register study, year not reported: death rate of people diagnosed between 6 and 17 years of age compared with the general population, mortality rate ratio 1.58. What the terms mean:
- Mortality rate ratio How many times higher the death rate was in one group than in the general population, so 1 means no difference.
- 95 % confidence interval The range of values the data are consistent with.
Source: Caye A, Swanson J, Thapar A, et al.. Life Span Studies of ADHD—Conceptual Challenges and Predictors of Persistence and Outcome. Current Psychiatry Reports (2016). doi:10.1007/s11920-016-0750-x