Major Finding: School-age children with ADHD are at increased risk of developing substance use in late adolescence, including drug use or dependence and cigarette smoking. The only significant independent risk factor for later substance use among children with ADHD was conduct disorder.
Data Source: Ten-year prospective, longitudinal case-control family study of ADHD youth (n = 361) and controls (n = 417) first assessed by comprehensive interview at about age 11 and, for most recent findings, at about age 20.
Disclosures: Dr. Wilens receives research support from numerous pharmaceutical companies that make medications used to treat ADHD. This study was funded exclusively by government grants, including from the National Institute of Mental Health.
LOS ANGELES — Early conduct disorder in children with attention-deficit/hyperactivity disorder (ADHD) predicts substance use disorders in adolescence and early adulthood, according to researchers who conducted a long-term prospective study on 778 children.
“I'm a child psychiatrist. I treat kids and work with families. I'd like to know in 10-year-olds, whom do I worry about?” said Dr. Timothy E. Wilens, a pediatric psychopharmacologist at Massachusetts General Hospital in Boston and lead investigator of a 10-year, prospective study of 361 children with ADHD and 417 matched controls.
Children aged 10-11 years and their families underwent extensive interviews, and at periodic intervals over the subsequent decade, culminating in a follow-up evaluation when subjects were in their early 20s.
His overall hypothesis—that ADHD in school-age children would confer an elevated risk of later substance use—was supported, with significant hazard ratios for any substance use of 2.15; alcohol use or dependence, 2.19; drug use or drug dependence, 4.12; and cigarette smoking, 3.21.
As expected, conduct disorder in a child with ADHD “solidly” and independently predicted substance use (hazard ratio, 5.26), including alcohol use or dependence (2.85), drug use or dependence (2.36), and cigarette smoking (2.74).
“We know conduct disorder is big,” he said at the annual meeting of the American Academy of Addiction Psychiatry.
“What you may not know is that you can identify it in a 10-year-old pretty clearly, and if you see it in a 10-year-old, you know you're going to have a problem in adolescence.”
What failed to materialize in the study was a hypothesized link to other independent risk factors for eventual substance use in children with ADHD.
Early difficulties with socialization, family environment, school performance, full-scale IQ or the digit span subtest, arithmetic skills, and a family history of ADHD or substance use all failed to significantly increase the risk of substance use over and above the baseline risk faced by children with ADHD.
Similarly, neither depression nor anxiety independently increased risk for substance use.
“Remember, we have a bit of a ceiling effect here,” cautioned Dr. Wilens, who nonetheless expressed surprise at the results.
One strong trend that failed to reach significance because of a small sample size was a possible link between bipolar disorder and later substance use in children with ADHD.
Previous studies conducted by Dr. Wilens and his group also have drawn associations between substance use among older children with ADHD when they have experienced parental substance use during certain vulnerable developmental stages, he said.
Overall, however, Dr. Wilens said the study suggests that children with ADHD who do not have conduct disorder or severe mood dysregulation face a baseline elevated risk of substance abuse that is not exacerbated by other comorbidities.
He drew attention to a large body of research showing that substance use initiation is delayed if children with ADHD are well managed with medication, although the protective effects of medication are lost in adulthood.
“Aggressively treating the ADHD is really critical,” he said.
He also advised careful assessment of potential conduct disorder in young children, which may present as a history of aggressiveness, bullying, a dearth of positive interactions with other children, harm to animals or younger children, a problematic response to parental discipline, and a lack of empathy.
Minor property damage such as breaking windows might be part of the picture in a 10-year-old, but conduct disorder is likely to look different in younger children, Dr. Wilens said.
“You're not going to see them stealing a car.”