The relationship between attention-deficit hyperactivity disorder (ADHD) and substance use in children is hotly debated. ADHD symptoms include inattention, hyperactivity/impulsivity and conduct disorders, and there’s considerable interest in finding out which of these predicts early substance use. If we have reliable evidence that answers this question we can make informed decisions about treating ADHD and potentially reducing future substance misuse.
A new prospective cohort study uses data from a Swedish database of 1,480 pairs of twins born in 1985-86. The study looks at the different ADHD symptoms to see which increase the risk of substance misuse in young teenagers and whether the risk is greater in individuals with persistent symptoms.
The authors measured ADHD symptoms and conduct problems at two stages:
- Age 8-9 years
- Age 13-14 years
Risk factors were measured at both stages using parent reported checklists, parent completed questionnaires and patient self-reports, which have not been formally validated.
The outcomes of interest were tobacco, alcohol and illicit drug use in the last year:
- Tobacco ‘sometimes’ use was ‘1-2 times’ or ‘once in a while’, more frequent use was ‘often’
- Feeling intoxicated from alcohol ‘1-10 times’ was ‘sometimes’ use, more frequent use was ‘often’
- Illicit drug use was not subdivided in this way
Here’s what they found:
- Hyperactivity/impulsivity at ages 8–9 is independently associated with occasional tobacco use at ages 13–14
- Hyperactivity/impulsivity that persists between ages 8–9 and 13–14 also predicts sometimes alcohol use at ages 13–14
- Inattention at ages 8–9 or persistent inattention to ages 13–14 are not independently associated with early-onset substance use
The authors concluded:
Our results indicated that hyperactivity/impulsivity, but not inattention, is an important early predictor for early-onset substance use, and a shared genetic susceptibility is suggested to explain this association.
Chang Z, Lichtenstein P, Larsson H. The effects of childhood ADHD symptoms on early-onset substance use: a Swedish twin study. J Abnorm Child Psychol. 2012 Apr;40(3):425-35. [PubMed abstract]