Frequent cannabis use in Ontario youth was linked to both internalizing and externalizing symptoms, especially in girls | Research

The takeaway

Among Ontario youth aged 12-17, frequent cannabis use was associated with elevated anxiety/depression symptoms and conduct/ADHD symptoms, with significantly stronger associations in females than males.

Parents, school counselors, pediatricians, and youth mental health researchers.

Externalizing symptoms OR: 5.13 in females vs 2.17 in males

What the researchers found

Frequent cannabis use was associated with elevated externalizing symptoms (OR 2.17 in males, 5.13 in females) and internalizing symptoms (OR 2.07 in males, 3.40 in females). These associations persisted after adjusting for binge drinking, smoking, and parenting factors.

Why it matters

The markedly stronger associations in females suggest that girls who use cannabis frequently may be particularly vulnerable to mental health effects, which has implications for targeted prevention.

The numbers in context

Externalizing: OR 2.17 (1.80-2.62) males, 5.13 (4.24-6.21) females. Internalizing: OR 2.07 (1.74-2.47) males, 3.40 (2.73-4.24) females. Associations persisted after adjusting for confounders.

How the study worked

Cross-sectional analysis of the 2014 Ontario Child Health Study using the Emotional and Behavioural Scales. Logistic regression estimated associations between cannabis use frequency and elevated symptoms, with replicate bootstrap weighting for design effects.

What this study cannot tell us

Cross-sectional design cannot determine whether cannabis use preceded or followed the development of symptoms. Self-reported cannabis use may be underreported. The study cannot distinguish between different cannabis products or potencies.

How to read the evidence

Moderate: large population-based sample with validated measures, though cross-sectional design limits causal inference.

When this study was published

Published in 2020 in Journal of Adolescent Health.

The bigger picture

The sex difference in the strength of associations raises important questions about whether biological factors, social context, or both explain why frequent cannabis use appears more strongly linked to mental health symptoms in girls.

Questions still open

Why are associations stronger in females? Do girls with mental health symptoms use cannabis to self-medicate, or does cannabis affect girls differently? Would longitudinal data confirm these cross-sectional associations?

Common questions

What are internalizing and externalizing symptoms?

Internalizing symptoms are directed inward, like anxiety and depression. Externalizing symptoms are directed outward, like conduct problems and attention difficulties. This study found frequent cannabis use was associated with both types.

Why were effects stronger in girls?

The study found that associations between frequent cannabis use and both types of symptoms were 2-3 times stronger in females. The reasons are unclear but could involve biological differences in how THC is processed, different patterns of use, or different social contexts.

Read the original research

Cannabis Use and Internalizing/Externalizing Symptoms in Youth: A Canadian Population-Based Study.

The Journal of adolescent health : official publication of the Society for Adolescent Medicine, 67(1), 26-32

View on PubMed ↗Publisher’s paper ↗

Citation

Girgis, Joseph; Pringsheim, Tamara; Williams, Jeanne; Shafiq, Samreen; Patten, Scott. (2020). Cannabis Use and Internalizing/Externalizing Symptoms in Youth: A Canadian Population-Based Study.. The Journal of adolescent health : official publication of the Society for Adolescent Medicine, 67(1), 26-32. https://doi.org/10.1016/j.jadohealth.2020.01.015