Am Fam Physician. 2024;109(4):369-370
Author disclosure: No relevant financial relationships.
Clinical Question
Are adolescents with a history of cannabis use more likely to develop increased suicidality in adulthood?
Evidence-Based Answer
Adolescents with a history of cannabis use have at least a 50% increase in the odds of developing suicidality in adulthood. (Strength of Recommendation: B, large meta-analysis of cohort studies consistent with an additional cohort and cross-sectional twin study.)
Evidence Summary
A 2019 systematic review and meta-analysis (11 prospective cohort studies; n = 23,317) assessed the association between adolescent cannabis use and the risk of developing depression, anxiety, and suicidality in young adulthood.1 Included studies enrolled patients younger than 18 years and assessed their cannabis use before 18 years of age with self-reported questionnaires that measured frequency of use over the past 6 to 12 months. Patients with any reported use were pooled and compared with nonusers. All studies individually adjusted the odds ratios (ORs) based on several suspected confounding variables, including a history of depression, alcohol use, sex, or tobacco use. The primary outcomes included rates of suicidal ideation and suicide attempts, assessed by questionnaire or standardized interview assessments at least once between 18 and 32 years of age. A history of cannabis use in adolescence was associated with a 50% increase in the odds of suicidal ideation (three studies; n = 8,479; OR = 1.5; 95% CI, 1.1 to 2.0) and more than a threefold increase in the odds of a suicide attempt (three studies; n = 13,687; OR = 3.4; 95% CI, 1.5 to 7.8) in adulthood. Some studies did not account for potential confounders such as tobacco or other drug use and comorbid psychosocial factors. The exact type, quantity, and potency of cannabis consumed among the studied adolescents were not measured or reported.
A 2020 prospective cohort study (n = 581) evaluated whether cannabis use in adolescence was associated with depression, suicidality, and anxiety disorders in adulthood.2 Researchers identified patients 19 and 20 years of age from Zurich, Switzerland, in 1979. An initial screening questionnaire that included frequency of use and age at first use retrospectively assessed participants' cannabis use. The primary outcomes included the rate of suicidality (defined as serious, persisting suicidal thoughts; suicidal ideation with a plan; or suicide attempts), and patients were assessed over the following 30 years with seven waves of structured interviews. Cannabis use during adolescence was associated with increased odds of suicidality (adjusted OR = 1.6; 95% CI, 1.1 to 2.4). Study limitations included the risk of recall bias with a retrospective assessment of cannabis use and the type of cannabis that was used. There was no assessment of confounding factors such as comorbid mental health conditions in adolescence or additional socioeconomic factors.
A 2004 cross-sectional twin study (n = 2,765 twin pairs) examined a potential association between cannabis use and major depressive disorder or suicidality.3 Researchers conducted phone interviews with adult twin pairs (median age = 30 years) drawn from a national registry in Australia. They identified 277 same-sex twin pairs who were discordant for lifetime cannabis dependence (defined as use more than once per month after 17 years of age) through a structured interview (adapting the Semi-Structured Assessment for the Genetics of Alcoholism). They further identified 311 pairs who were discordant for early-onset cannabis use (i.e., use before 17 years of age). Outcomes included the rate of suicidality, which was assessed during the same structured interview and defined as a reported history of previous suicidal ideation or suicide attempts. Twins who used cannabis had higher odds of comorbid suicidal ideation (adjusted OR = 2.8; 95% CI, 1.7 to 4.7) and previous suicide attempts (adjusted OR = 2.5; 95% CI, 1.1 to 5.6) than their nonusing twin. Twins who reported early-onset cannabis use had increased rates of suicide attempts (adjusted OR = 3.4; 95% CI, 1.4 to 8.5) but not suicidal ideation. Limitations included those inherent to cross-sectional study designs, including the inability to assess a temporal relationship, the risk of recall bias, and no accounting for the frequency of cannabis use or the type or quantity used.
Copyright © Family Physicians Inquiries Network. Used with permission.
