Externalizing disorders like conduct problems predicted cannabis use disorder, but depression and anxiety did not | Research

The takeaway

In 816 people followed from age 16 to 30, externalizing disorders (conduct problems, ADHD-like behaviors) from prior years predicted cannabis use disorder onset, but internalizing disorders did not.

Read this if you want to understand what predicts who develops cannabis dependence.

Externalizing disorders predicted CUD; depression and anxiety did not

What the researchers found

Researchers followed 816 participants through four diagnostic assessments between ages 16 and 30 to determine which psychiatric problems preceded the development of cannabis use disorders (CUDs). Using time-to-event analyses, they found that externalizing psychopathology from the developmental period just before CUD onset was a robust predictor.

Internalizing disorders (depression, anxiety) did not predict CUD onset in either unadjusted or adjusted analyses. This finding held even after controlling for other psychiatric comorbidities.

However, a large proportion of individuals who developed CUDs had no prior externalizing or internalizing psychopathology at all, indicating that psychiatric history is an incomplete predictor. The results suggest externalizing disorders are a useful risk marker but not the whole story.

Why it matters

Identifying who is at risk for developing cannabis use disorders can guide prevention efforts. The finding that externalizing behaviors (but not anxiety or depression) predict CUD onset suggests that prevention programs should focus on youth with behavioral problems rather than those with mood disorders.

The numbers in context

816 participants, ages 16-30. 4 assessment points. Externalizing disorders from proximal periods predicted CUD onset. Internalizing disorders were non-predictive. Many CUD cases had no prior psychiatric history.

How the study worked

Prospective longitudinal study with 816 participants completing 4 diagnostic assessments between ages 16 and 30. Current and past cannabis use disorders and full psychiatric disorder histories were assessed. Time-to-event analyses (unadjusted and adjusted) evaluated externalizing and internalizing psychopathology as CUD predictors.

What this study cannot tell us

Limited to one cohort from Oregon. Four assessment points may miss disorders occurring between assessments. "Externalizing psychopathology" encompasses multiple disorders that may carry different risks. The finding that many CUD cases had no prior psychopathology limits predictive utility.

How to read the evidence

Longitudinal cohort study with four assessment waves spanning 14 years. Strong design for testing temporal predictors.

When this study was published

Published in 2015 with data spanning ages 16-30.

The bigger picture

The common assumption that people use cannabis to self-medicate depression and anxiety, leading to dependence, is not supported by this longitudinal data. Instead, the pathway from externalizing behaviors to cannabis problems suggests impulsivity and conduct-related traits drive risk more than emotional distress.

Questions still open

What other factors predict CUD onset in people without prior psychiatric problems? Does treating externalizing disorders in youth reduce CUD risk? Would the internalizing pathway be more relevant in older populations?

Common questions

Does depression lead to cannabis dependence?

In this longitudinal study, depression and anxiety did not predict the development of cannabis use disorders. Instead, externalizing problems like conduct disorders were the psychiatric predictors, suggesting the self-medication hypothesis for mood disorders may not apply.

Can we predict who will develop cannabis problems?

Externalizing disorders from recent developmental periods were a robust predictor, but many people who developed cannabis use disorders had no prior psychiatric problems. Psychiatric history is informative but incomplete as a predictor.

Read the original research

Internalizing and externalizing psychopathology as predictors of cannabis use disorder onset during adolescence and early adulthood.

Psychology of addictive behaviors : journal of the Society of Psychologists in Addictive Behaviors, 29(3), 541-51

View on PubMed ↗Publisher’s paper ↗

Citation

Farmer, Richard F; Seeley, John R; Kosty, Derek B; Gau, Jeff M; Duncan, Susan C; Lynskey, Michael T; Lewinsohn, Peter M. (2015). Internalizing and externalizing psychopathology as predictors of cannabis use disorder onset during adolescence and early adulthood.. Psychology of addictive behaviors : journal of the Society of Psychologists in Addictive Behaviors, 29(3), 541-51. https://doi.org/10.1037/adb0000059