Adolescent cannabis use was linked to depression, but more frequent use did not always mean worse depression | Research

The takeaway

Among nearly 88,000 adolescents in a national survey, any cannabis use history was associated with higher rates of depression and suicide attempts, but the relationship between use frequency and depression was unexpectedly non-linear.

Adolescent mental health clinicians, parents, and substance use epidemiologists.

Any cannabis use linked to more depression, but frequency pattern was non-linear

What the researchers found

Adolescents with any cannabis use history had significantly higher rates of major depressive disorder and past-year suicide attempts. However, the association between use frequency and depression was counter to expectations: past-year users did not consistently show worse depression than those who used over a year ago.

Why it matters

The non-linear relationship between cannabis use frequency and depression challenges simple dose-response assumptions and suggests the cannabis-depression relationship is more complex than "more use equals more depression."

The numbers in context

14,873 cannabis users vs 73,079 never-users. Cannabis users had significantly higher rates of lifetime MDD, past-year MDD, MDD with severe impairment, and past-year suicide attempts (all p values significant).

How the study worked

Analysis of the National Survey on Drug Use and Health (2012-2017). 14,873 adolescents with cannabis use history were compared to 73,079 never-users using weighted logistic regression controlling for demographics and other substance use.

What this study cannot tell us

Cross-sectional design cannot establish whether cannabis use preceded depression or vice versa. Self-reported data in adolescents may be unreliable. The frequency-depression pattern requires replication and further investigation.

How to read the evidence

Strong: very large nationally representative sample with statistical controls, though cross-sectional design.

When this study was published

Published in 2020 in Drug and Alcohol Dependence.

The bigger picture

The unexpected pattern between frequency and depression suggests that factors beyond simple exposure, such as reasons for use, social context, or self-medication, may drive the association between cannabis use and depression in adolescents.

Questions still open

Does the non-linear pattern suggest that some adolescents use cannabis to cope with pre-existing depression? Could different motivations for use explain the unexpected frequency-depression relationship?

Common questions

Does cannabis cause depression in teenagers?

This study found an association but cannot prove causation. Adolescents who used cannabis had higher rates of depression, but it is unclear whether cannabis caused the depression, the depression led to cannabis use, or both share common risk factors.

What was unexpected about the results?

The researchers expected a straightforward dose-response pattern where more frequent cannabis use would predict worse depression. Instead, the pattern was non-linear, with past-year users not consistently showing worse outcomes than those who used more than a year ago.

Read the original research

Relationship between cannabis use frequency and major depressive disorder in adolescents: Findings from the National Survey on Drug Use and Health 2012-2017.

Drug and alcohol dependence, 208, 107867

View on PubMed ↗Publisher’s paper ↗

Citation

Gukasyan, Natalie; Strain, Eric C. (2020). Relationship between cannabis use frequency and major depressive disorder in adolescents: Findings from the National Survey on Drug Use and Health 2012-2017.. Drug and alcohol dependence, 208, 107867. https://doi.org/10.1016/j.drugalcdep.2020.107867