New research published in Drug and Alcohol Dependence has found a complicated and counterintuitive relationship between cannabis use among adolescents and depression. The study found that adolescents who had used cannabis at any point were more likely to show symptoms of depression, but more frequent consumption was associated with reduced odds of depression among cannabis users.
“Depression and cannabis use often co-occur, but the reasons for this are still not fully understood. In this study, we attempted to determine whether frequency of cannabis use was associated with depressive symptoms,” said study author Natalie Gukasyan (@N_Gukasyan), a postdoctoral fellow at Johns Hopkins University School of Medicine.
“We chose to look at an adolescent population because this is a sensitive developmental period and is often the age of onset for both mood disorders and cannabis use. Given that prior studies have suggested that cannabis use may increase the risk of depression, we expected to find the highest rates of depression in those that used cannabis most frequently.”
The researchers examined data from 90,314 American adolescents who participated in the National Survey on Drug Use and Health. They found that depression was more prevalent among adolescents with any history of cannabis use compared to those with no history of cannabis use.
But among cannabis users, those who used the drug more frequently tended to have lower rates of depression than those who used it less frequently. Among users, 33.1% reported using cannabis 1 to 12 days in the past year, 14.6% reported using cannabis 13 to 51 days in the past year, and 32.7 % reported using cannabis more than 52 days in the past year.
“Any history of cannabis use in an adolescent, even if it was over a year ago, is associated with a higher risk of past year and lifetime major depressive episode. However, when we analyzed adolescents with any history of cannabis use, the higher frequency users had lower risk of depression compared to lower frequency users when other factors were accounted for,” Gukasyan told PsyPost.
“Among the subset of adolescents with any history of cannabis use, the highest rate of past year major depressive episode was found in those that had last used cannabis over a year ago.”
After controlling for other factors, the researchers found that heavy cannabis use was not associated with significantly different odds of past year depression compared to never users.
“It is difficult to draw conclusions about why we observed this pattern,” Gukasyan said. The researchers believe the findings could reflect differences in motives for using cannabis, “with some adolescents using for subjective relief of depression, and others using for social or other factors.”
Differences in access to treatments for depression could also play a role, as could some methodological limitations.
“This was based on self-reported data, which is subject to recall and other types of bias. Cannabis use frequency may not be perfectly correlated to amount or dose of cannabis used – e.g. a daily smoker might use the same absolute amount of cannabis as someone who smokes a large quantity once per week, yet these individuals could have been analyzed in separate groups,” Gukasyan explained.
“This analysis cannot conclude anything about the future risk of depression in cannabis users. Other studies, including prospective studies, have found that cannabis use during adolescence predicted higher likelihood of developing major depressive disorder and other mental health issues in adulthood.”
The study, “Relationship between cannabis use frequency and major depressive disorder in adolescents: Findings from the National Survey on Drug Use and Health 2012–2017“, was authored by Natalie Gukasyan and Eric C. Strain.