Depression in Canada: Cannabis Abuse and Dependence Found in About 5% of Those Affected | Research

The takeaway

Among Canadians with past-year major depression, 2.5% had cannabis abuse and 2.9% had cannabis dependence, while 63% sought treatment and 6.6% had attempted suicide.

Read this if you have depression and use cannabis, or are interested in the overlap between mood disorders and substance use.

2.5% cannabis abuse + 2.9% cannabis dependence among those with depression

What the researchers found

This national epidemiological survey assessed major depressive disorder in 25,113 Canadians using diagnostic interviews. The past-year prevalence of major depression was 3.9%.

Among those with depression, substance use was notable: 4.8% had alcohol abuse, 4.5% had alcohol dependence, 2.5% had cannabis abuse, and 2.9% had cannabis dependence. Generalized anxiety disorder co-occurred in nearly 25%.

Treatment seeking had improved compared to earlier Canadian surveys (63.1% sought treatment), but antidepressant use remained stable at 33.1%. A concerning 37.5% of those accessing treatment perceived stigma from others about their condition. Suicide attempts were reported by 6.6%.

Why it matters

This study quantifies the overlap between depression and cannabis use disorders in a national population, while also showing that depression remains significantly undertreated and stigmatized despite being common.

The numbers in context

25,113 respondents; past-year MDD prevalence 3.9%; cannabis abuse 2.5% and dependence 2.9% among those with MDD; 63.1% sought treatment; 33.1% on antidepressants; 6.6% attempted suicide; 37.5% perceived stigma

How the study worked

National population-based survey (Canadian Community Health Survey - Mental Health, 2012) of 25,113 respondents using an adaptation of the WHO Composite International Diagnostic Interview. Complex survey design methods were used for prevalence estimates.

What this study cannot tell us

Cross-sectional survey cannot determine causal direction between depression and cannabis use. Self-reported diagnoses and treatment. Household survey may miss homeless or institutionalized populations with higher depression rates.

How to read the evidence

Large national survey with validated diagnostic instruments and representative sampling, providing reliable population-level estimates.

When this study was published

Published in 2015 using 2012 data. Canada has since legalized recreational cannabis, which may have changed use patterns among those with depression.

The bigger picture

The co-occurrence of depression and cannabis use disorders raises questions about whether people use cannabis to self-medicate for depression or whether cannabis use contributes to depression. Either way, integrated treatment addressing both conditions may be beneficial.

Questions still open

Does cannabis use worsen depression outcomes, or are depressed people self-medicating with cannabis? Would addressing cannabis use improve depression treatment outcomes? Has stigma around depression decreased since 2012?

Common questions

How common is cannabis use among people with depression?

In this Canadian survey, about 5.4% of people with major depression had cannabis abuse or dependence (2.5% abuse, 2.9% dependence). This is higher than the general population rate, suggesting an association between the two conditions.

Does treating depression reduce cannabis use?

This study did not test that directly. It found that 63% of depressed Canadians sought treatment, but the relationship between depression treatment and cannabis use was not examined.

Read the original research

Descriptive epidemiology of major depressive disorder in Canada in 2012.

Canadian journal of psychiatry. Revue canadienne de psychiatrie, 60(1), 23-30

View on PubMed ↗

Citation

Patten, Scott B; Williams, Jeanne V A; Lavorato, Dina H; Wang, Jian Li; McDonald, Keltie; Bulloch, Andrew G M. (2015). Descriptive epidemiology of major depressive disorder in Canada in 2012.. Canadian journal of psychiatry. Revue canadienne de psychiatrie, 60(1), 23-30.