Children with ADHD Likelier to Use Marijuana, Drugs Later in Life

Brooke Molina, PhD

In adolescents and young adults with attention deficit hyperactivity disorder (ADHD), the frequent use of marijuana and cigarettes increases the risk of substance use later in life, according to a prospective, longitudinal study in the Journal of Child Psychology and Psychiatry.

“We found particularly high rates of marijuana use and cigarette smoking by adulthood in individuals with attention deficit hyperactivity disorder who used marijuana during adolescence,” lead investigator Brooke Molina, PhD, of the University of Pittsburgh told MD Magazine. “Given the current climate with so much changing regarding marijuana laws, we should be paying closer attention to this area of concern.”

A total of 547 children with ADHD (mean age 8.5 years) and 258 controls without ADHD were included in the prospective study. Investigators administered the Substance Use Questionnaire up to 8 times over 16 years. The questionnaires were completed by participants from age 10 to age 25 to determine the use frequency of marijuana, cigarettes, alcohol, and illicit drugs. The population was fairly heterogeneous, involving individuals of difference races and socioeconomic backgrounds who received care at 6 healthcare centers across the US and Canada.

Once children reached adulthood, those with ADHD were more likely to engage in weekly marijuana use compared to healthy controls (32.8% vs 21.3%) and more likely to smoke cigarettes daily (35.9% vs 17.5%). Participants with ADHD were also more likely to be users of all studied substances earlier in life than healthy controls (57.9% vs 41.9%).

In addition, the use of alcohol and non-marijuana illicit drugs increased at a slightly faster rate among adolescents with ADHD as compared to controls. Based on the longitudinal and cumulative data, the investigators found that early substance use was a noticeable predictor for faster substance use increases as well as more frequent substance use in adulthood for individuals with or without ADHD.

This study represents the first longitudinal analysis of substance use risk in children with ADHD, particularly in regard to marijuana use. Future longitudinal research with a greater patient population across different regions of the world may be necessary to validate these results.

Currently, the increasing availability of cannabis holds potential complications when it comes to the future health risk of children, particularly those with ADHD. The study results indicate a need for earlier screening strategies to help identify substance use in children and adolescents with ADHD. In doing so, clinicians can actively participate in the effort to reduce the likelihood of substance use or abuse later in life.

“We can’t just see what happens—we have to monitor the risk early and do our best to steer these children to healthy outcomes,” said Molina. “Children and teenagers who are involved in healthy activities as opposed to having too much free time on their hands can end up making healthier choices.”

According to Molina, things such as staying physically active and performing well in school are important activities that should be reinforced to help prevent substance use or abuse.

The study, “Substance use through adolescence into early adulthood after childhood-diagnosed ADHD: findings from the MTA longitudinal study,” was published in the Journal of Child Psychology and Psychiatry.