Two recent studies find that being diagnosed with attention deficit hyperactivity disorder (ADHD) in childhood may predict a child’s likelihood of later dependence on nicotine, alcohol or other drugs.
One new paper, which was published this month in Clinical Psychology Review, was a review of 27 previous studies that followed 4,100 children with ADHD and 6,800 kids without the disorder, from childhood to young adulthood. Psychologists at University of California, Los Angeles, and University of South Carolina, Columbia, found that kids diagnosed with ADHD were three times more likely to become dependent on nicotine, twice as likely to use cocaine and 1.5 times more likely to use marijuana, compared with kids who did not have the behavioral disorder.
(More on TIME.com: Study: Preterm Birth Raises the Risk of Childhood ADHD)
The other paper, led by Dr. Alice Charach, a child psychiatrist at The Hospital for Sick Children in Toronto, was also a review of previous research (the two meta-analyses included 10 of the same studies), but came to a somewhat weaker conclusion. It found a significant association between childhood ADHD and nicotine use in adolescence as well as alcohol use in young adulthood, but a less certain link with illegal drug use.
Reported Scientific American:
In contrast, Charach’s team — which published its review in the January issue of the Journal of the American Academy of Child & Adolescent Psychiatry — also found an increased risk for marijuana and other drugs, but decided the results of the individual studies examined were too varied to reach a strong conclusion. Overall, however, “the similarities outweigh the differences” between the two meta-analyses, Charach says. Steve Lee, lead researcher on the U.C.L.A. review, agrees, “I think both studies are collectively persuasive.”
(More on TIME.com: Does Your Baby Cry Too Much at Night? It Could Signal Future Behavior Problems)
Why exactly ADHD may increase kids’ risk of substance dependence is unclear, but the researchers suggest it may have to do with the stress and anxiety that often accompany the disorder. Kids with ADHD have trouble focusing at school and controlling their impulsive urges, so they don’t make friends as easily as other children and have difficulty learning. It’s possible that substance use may help relieve some of that stress. Alternatively, there may be an underlying reason that kids are predisposed to both ADHD and substance use.
(More on TIME.com: The Lab Rat: A Better Way to Diagnose ADHD)
Parents should remember, however, that an ADHD diagnosis is by no means a guarantee of later drug use. What’s more, given that ADHD is typically identified early — affecting about 5% to 7% of school-age children, and appearing around age 8 or 9 — it gives parents time to start talking to their kids about making good choices early on.
But as children enter their teenage years, the authors advise parents to remain vigilant for signs of drug abuse like changes in children’s choice of friends, mood swings or depression, and declines in academic performance.