Cannabis Use Increases Depressive and Suicidal Thinking

Cannabis use has become increasingly normalized in the United States, and at least half the states have “medical marijuana” laws. This reversed criminalization, but rather than following FDA-like testing and approval, cannabis was suddenly "a medicine." Access to cannabis or its intoxicant THC has never been greater. Adolescents may not legally purchase cannabis; however, their access has increased.

Cannabis is largely unstudied or has failed rigorous medication trials, so its impact on mental health is mostly unknown. However, new findings indicate distressing results, causing experts to call for a reassessment of the risks and benefits of cannabis, as nearly 30% of users develop cannabis use disorder (CUD). For adolescent users, risks for addiction are twice that of adults, and after four years, 1 in 5 adolescents develop problematic use. Disturbingly, new studies suggest elevated cannabis risks for depression and suicidal thoughts and behaviors, especially in adolescents and young adults.

A Self-Medication Tragedy

A CDC study of 16,000 adolescents 13-18 years old found the most common reasons for marijuana/THC use were: to feel calm or relaxed (73%), have fun/experiment (50%), sleep better (44%), forget problems/ memories (44%), and alleviate anxiety or depression (40%). In contrast, a cohort of adults reported these primary uses: stress management (58%), anxiety relief (36%), and headache/pain relief (~11%) and self-medication reasons; others used the drug “to feel well” (83%) or “forget life’s problems” (20.6%).

A new article in Drug and Alcohol Dependence delves into the relationships between cannabis use, depression, and suicidal behaviors. After adjusting for depression, adolescent cannabis use was significantly associated with increased risks for thinking about suicide and more than double the risk for suicide attempts. Among adolescents, cannabis use was linked to a 1.85 times higher likelihood of attempting suicide.

Depression may contribute to the relationship between cannabis use and suicidality, but doesn’t fully explain it, suggesting cannabis use poses independent risks for suicidal thoughts and behaviors. Cannabis may act as a catalyst, accelerating depressive processes.

Cannabis for Teens Should Be Considered Dangerous Until Proven Safe

Even FDA-approved medication use is a concern in young people. In contrast to adult FDA trials, pediatric trials are very closely monitored due to stricter ethical considerations. Pediatric trials include enhanced monitoring for suicidality, given increased risks of suicidal thoughts and behaviors in younger populations—a concern that led to the FDA’s black box warning on all antidepressants for individuals under age 25. (And as noted earlier, there were no successful adult or adolescent drug trials of cannabis for depression.)

Additionally, pediatric drug studies that occur monitor potential effects on growth and neurodevelopment. Informed consent processes are complex, requiring parental consent along with age-appropriate assents from children/adolescents. Long-term follow-up is often more critical in pediatric studies to assess the impact of the drug over time on physical and psychological development. But none of this research was performed with cannabis.

Corroborating Studies on Cannabis and Depression

Recent high-quality studies reinforce findings that cannabis use during adolescence can predict increases in depressive symptoms and suicidal ideation. Gobbi et al. in JAMA Psychiatry reported a strong association of cannabis use in adolescence to risks for depression, anxiety, and suicidality in young adulthood. For example, cannabis use in adolescence was associated with an increased risk for major depression and suicidal ideation (about 1.5 times greater). Much worse, adolescent cannabis was associated with suicide attempts in young adulthood (3.4X greater).

A longitudinal study of 2,000+ Norwegians from adolescence into their late 20s found frequent adolescent cannabis use (≥11 times/year) correlated with nearly a three times greater risk for suicide attempts in adulthood. In a 21-year study in New Zealand of individuals ages 14-21 years later followed up, cannabis use frequency and psychosocial outcomes were linked to depression, suicidal ideation, and suicide attempts. Frequent adolescent cannabis use (weekly or more) predicted higher risks of later suicidal ideation and attempts. Cannabis use was also significantly associated with increased suicidal thoughts after adjustments for other factors, such as other substance use.

Cannabis Essential Reads

Early Cannabis Use Linked to Memory Slowdown in Teens

The Sober Curious Movement's Big Blind Spot

A major study in Proceedings of the National Academy of Sciences compared a large sample of hospitalized adolescents with cannabis use disorder (CUD) vs. those without CUD and controlled for depression. Adolescents with CUD had substantially increased odds of suicide attempts and self-harm; the presence of comorbid depression more than doubled risks.

Prior studies have shown that cannabis use during adolescence or young adulthood is linked to higher risks of depression, suicidal ideation, and suicide attempts. High-dose exposures via high-potency cannabis or vaping THC use are also associated with an increased risks.

Adolescent Cannabis Use and Future Depression and Suicidality

Some researchers examined the association between cannabis use in adolescence and later adult depression, suicidality, and anxiety disorders. In a cohort of young adults (n = 591) from Zurich, Switzerland, subjects ages 19/20 were asked about past cannabis use in adolescence. In this study, adolescent cannabis use was associated with adult depression and suicidality. Younger age at first cannabis use and more frequent use in adolescence related to a particularly increased risk for adult depression.

A study in Frontiers in Public Health found cannabis use associated with higher risks of major depressive disorder, as well as suicidality. Another study demonstrated that adolescents with cannabis use disorder (CUD) symptoms were more severely ill than adults, suggesting a developmental vulnerability. Experts concluded youth cannabis use likely fuels depression and suicide in young people.

Adolescent users had a persistently higher severity of cannabis use disorder symptoms compared to adults. The earlier the use, the more severe the patterns. Cannabis targets the brain to change thoughts, moods, and behavior. Although it does not produce overdoses, it can lead to schizophrenia, accidents, depression, and suicide. As Harvard Professor Bertha Madras said in May 2024. “This is not a war on drugs. It’s a defence of the human brain at every possible age from in utero to old age.” 

Summary

Multiple recent studies have presented convincing evidence supporting likely causal pathways from youth cannabis use to depression and suicidal outcomes in adolescence and adulthood. Trauma or minority stress and self-medication heighten vulnerability, making cannabis a perceived treatment or coping mechanism in the absence of FDA-approved treatments, psychological support, or treatment.

Depressed patients should be assessed for cannabis use as a possible additional risk factor for suicidal behavior. Also, cannabis users in turn should be assessed for depression and suicidal behaviors. Lastly, future cohort studies should track the onset timing of cannabis use, depressive symptoms, and suicidal behaviors.