Cannabis, Alcohol and Suicide

A comparison was conducted of cannabis, alcohol and drug use in 12,750 persons (ages 16 years +) who died of suicide and 43,465 case control cases in 2013 in the US. This large-scale study provides critical insights into how substances affect suicidal behaviour, as well as their links to anxiety and depression.

Positive postmortem blood THC results were detected in 17.1% of the suicide victims and 7.2% of the control cases. This means suicide victims were more than twice as likely to have THC in their system compared to the control group. However, postmortem blood alcohol concentrations were found in 39.5% of the suicide victims compared to 2.4% of the controls. The adjusted odds ratio of suicide were:

THC – 1.83X
Alcohol – 20.53X

These numbers show that while cannabis does increase suicide risk, alcohol remains a far more significant factor. However, this study may underestimate the current risk of suicide with cannabis use as it was based on 2013 data, before widespread legalization and the large increase in THC potency of cannabis products. Today’s cannabis is much stronger than what was available in 2013, which may worsen anxiety and depression in vulnerable users.

Although the previous study did not determine the mode of suicide, another study using 21,894 suicide victims who died in Sweden between 1994 and 2009 showed an increased adjusted odds ratio of suicide victims who jump from heights on THC. This Swedish research broke down suicide methods to identify which ones are most strongly linked to specific substances.

Cannabis is mostly used for its relaxing effect, but the drug has several psychiatric side effects, including worsening anxiety and depression. Jumping from a height is a method related to psychopathology and cannabis is associated with confusion and drug-related psychosis. A case report also showed suicide ideation with cannabis use for jumping from a height. The data reveals that for jumping from a height, THC had an adjusted odds ratio of 1.62X, which is significantly higher than alcohol at 0.44X for the same method.

For other methods such as hanging, drowning, firearm, and sharp force, THC showed reduced odds ratios ranging from 0.36X to 0.8X. This suggests that THC does not increase risk for all suicide methods equally. Instead, it appears to be uniquely dangerous for impulsive, high-risk behaviours like jumping from a height, especially in individuals already struggling with anxiety and depression.

A 32-year-old man attended an ER for psychiatric help. He had smoked cannabis a few hours before and now felt hopelessness, anxiety, fear, and agitation, and had the impulse to commit suicide by falling from a height. He had a similar episode three years earlier after smoking cannabis, which resolved in a few hours. He reported no stressful life events. His urine toxicology screen was only positive for cannabinoids. He was treated with 4mg of risperidone and 1000mg of valproate and was released the next day.

This case presents two original clinical aspects:

• Episodic cannabis use induced suicidal ideation abruptly
• Suicidal ideation appeared independent of mood depression, stressors, or life events

There seems to be no linear relation between the severity of anxiety and depression and the risk of suicide. In some patients, high suicidal risk may be concomitant with relatively minor depressive states, while in others, extremely severe depression may be immune to suicidal risk.

Shi and Li (2025) concluded that:

“Cannabis use is a significant risk factor for suicide, independent of alcohol use and demographic characteristics. Policy makers should take into consideration the excess risk of suicide associated with cannabis use when assessing the externalities of legalizing cannabis.”

References:

Lundholm, L.., Thiblin, I., Runeson, B., et al., “Acute Influence of Alcohol, THC or Central Stimulants on Violent Suicide: A Swedish Population Study”, Journal of Forensic Sciences, 59: 436-440, 2014
Shi, Q., and Li, G., “Cannabis Use and Suicide: A Case-Control Study Based on Integrative Data Analysis” Journal of Cannabis Research, 7: 93, 2025