Cannabis Use, Depression, Anxiety and Suicidality in Young Adults – Interpreting the Headline

On February 13th, the Journal JAMA Psychiatry, published a meta-analysis reviewing the possible link between cannabis use in adolescence and young adults and mental illness. You may have seen the headlines:

Teenage cannabis use linked to depression in later life or Pot use linked to higher risk of depression, suicide in teens: study, which state that up to 25,000 Canadian young people are diagnosed with depression due to cannabis use.

This data is scary, considering the highest consumers of cannabis occurs in young adults. Depression and other mental illnesses also have a significant impact on the patient and his/her family. The estimated cost of mental illness to the Canadian Health Care system $51 billion per year.

Beyond the Headlines – What Did the Study Find?

The meta-analysis used data from 11 studies with 23,317 individuals. They evaluated the outcomes of:

  • Depression in young adulthood
  • Anxiety in young adulthood
  • Suicide ideations
  • Suicide Attempts

Depression in Young Adulthood

To estimate the extent to which cannabis use during adolescence was associated with increased odds of developing depression in young adulthood, the authors pooled results from 7 studies. The pooled odds ratio (OR) for depression during young adulthood among cannabis users compared with nonusers was:

  • 1.37 (95% confidence interval (CI), 1.16-1.62)

Anxiety in Young Adulthood

The anxiety results were from 3 studies. The pooled OR for anxiety during young adulthood was:

  • 1.18 (95% CI, 0.84-1.67) (not statistically significant)

Suicidal Ideation and Attempts

Suicidal ideation is a symptom of depression, while suicide represents one of the most severe sequelae of mental illness. Results from 3 studies found the OR for suicide ideation within adolescence and young adulthood was:

  • 1.50 (95%CI, 1.11-2.03)

For suicide attempts within adolescence and in young adulthood:

  • 3.46 (95% CI, 3.46, 1.53-7.84)

What About the Limitations of this Meta-Analysis?

The limitations of these studies are intrinsic when looking at population data. We see there is a link between cannabis use and depression/suicide ideation/suicide attempts, but we can’t say that cannabis use caused the mental illness. We are not sure if people at risk of these mental health conditions are at higher risk of cannabis use, versus cannabis causing the mental illness.

Many of the studies used for the report did not adjust for other drugs of abuse and cigarettes, or psychosocial factors (ie, school abandonment, drug abuse in peers) that may be linked to depression and early cannabis consumption.

Some of the studies used different methods to assess depression. This could potentially lead to different rates of depression among the different studies.

Lastly, the amount of THC in recreational cannabis has changed significantly over the last decade. This could have a potential impact on the data as we interpret this data.

Author’s Conclusion

“Although individual-level risk remains moderate to low and results from this study should be confirmed in future adequately powered prospective studies, the high prevalence of adolescents consuming cannabis generates a large number of young people who could develop depression and suicidality attributable to cannabis.”

What Does This Mean for Your Patients?

Cannabis use (specifically THC) is not recommended in people under the age of 25 years of age. The Canadian Paediatric Society and the American Academy of Pediatrics both have published position statements on the use of cannabis in pediatrics. Both strongly discourage the use in adolescents and young adulthood due to the possible effects on the developing brain.

Looking at all the data, I think it is important for healthcare professionals to communicate the potential risks of using cannabis in young adults. Although the picture is not completely clear, the data is continuing to suggest that young adults using cannabis with THC are at elevated risk of negative outcomes. We should at least be discussing that this drug is not 100% safe in young people and there are some inherent risks with use.

It is important to note that this data applies to recreational use and not for the medical use of CBD dominant strains for specific conditions. As with any medical treatment it is crucial for the clinician to balance the risks and benefits in a specific patient.


Gobbi G, Atkin T, Zytynski T, et al. Association of Cannabis Use in Adolescence and Risk of Depression, Anxiety, and Suicidality in Young Adulthood: A Systematic Review and Meta-analysis. JAMA Psychiatry. February 2019. doi:10.1001/jamapsychiatry.2018.4500