Adults tend to use cannabis more frequently if they had elevated depressive symptoms in adolescence, but this does not appear to be the case among adults with a history of attention-deficit/hyperactivity disorder (ADHD), according to new research.

The findings have been published in the Journal of Abnormal Child Psychology.

“This study was one part of a larger project investigating how important developmental changes relate to substance use and disorder for young people who were diagnosed with attention-deficit/hyperactivity disorder as children,” said study author Andrea L. Howard, an associate professor of psychology at Carleton University.

“We have massive amounts of data on a large sample of children with ADHD who were followed from about age 8 into their mid-twenties, and we wanted to learn more about links between depression and substance use over time.”

The researchers examined data from the Multimodal Treatment Study of ADHD, a longitudinal study that initially recruited hundreds of children and followed them into adulthood. Their sample included 547 children diagnosed with ADHD and 258 age- and sex-matched comparison children.

Howard and her colleagues were particularly interested in this data because it included assessments of substance use, depressive symptoms, ADHD symptom persistence in adulthood, and several sociodemographic variables.

The researchers found that depressive symptoms were linked to the use of drugs and alcohol in adolescence. But depression did not appear to exacerbate the effects of childhood ADHD on substance use.

“There are two important takeaways from this study: First, we did find that feeling depressed at any particular age in adolescence was associated with using substances more heavily, but this association was small and applied to people with and without ADHD. In other words, there was no special depression-related risk for substance use associated with having a childhood history of ADHD,” Howard explained to PsyPost.

“Second, we found that depression in adolescence didn’t really predict adult substance use. The one exception was for cannabis (marijuana), where we saw the expected association only for young people without a history of ADHD: They tended to use cannabis less often if they were less depressed as teens.”

“What initially surprised us was that adolescent depression was totally unrelated to young adult cannabis use for those with a history of ADHD — they were using cannabis at fairly high rates no matter what. This led us to speculate on some of the reasons for generally widespread use, including the fairly widespread notion (that has not been demonstrated empirically) that cannabis might help reduce ADHD symptoms and related impairments,” Howard said.

But — like all research — the study includes some limitations.

“Our findings are consistent in some ways with other published work, but the exact analyses we did for this study have not been replicated in other data, so there is always the possibility that these findings are ‘false positives.’ I would be especially cautious about our finding related to adolescent depression and adult cannabis use, because we only found this for one substance out of four,” Howard explained.

The study, “Depression and ADHD-Related Risk for Substance Use in Adolescence and Early Adulthood: Concurrent and Prospective Associations in the MTA“, was authored by Andrea L. Howard, Traci M. Kennedy, Erin P. Macdonald, John T. Mitchell, Margaret H. Sibley, Arunima Roy, L. Eugene Arnold, Jeffery N. Epstein, Stephen P. Hinshaw, Betsy Hoza, Annamarie Stehli, James M. Swanson, and Brooke S. G. Molina.