Cannabis Use in Adolescence Linked to Increased Psychiatric Disorder Risk, Large Study Finds

A recent longitudinal study, encompassing over 460,000 adolescents, has identified an association between cannabis use during teenage years and an increased risk of developing psychiatric disorders, including psychotic, bipolar, depressive, and anxiety disorders, by young adulthood.

The research indicated that cannabis use generally preceded these diagnoses.

Introduction to the Study

A longitudinal cohort study has established a link between cannabis use in adolescents aged 13 to 17 and an elevated risk of psychiatric disorders later in young adulthood. The study, conducted by researchers from Kaiser Permanente, the Public Health Institute, the University of California, San Francisco, and the University of Southern California, analyzed health data from over 460,000 participants.

Study Design and Scope

• Data Source: The study utilized electronic health record data from routine pediatric visits within the Kaiser Permanente Health System in Northern California, covering the period between 2016 and 2023.
• Participants: It included 463,396 adolescents aged 13 to 17.
• Follow-up Period: Participants were followed through age 26 or until December 31, 2023.
• Exclusions: To investigate if cannabis use preceded psychiatric conditions, adolescents exhibiting symptoms of mental illnesses before cannabis use were excluded from the analysis.
• Funding: The research was funded by NIH’s National Institute on Drug Abuse.

Key Findings on Psychiatric Disorders

The study's findings highlight associations between adolescent cannabis use and the development of specific psychiatric conditions.

• Psychotic and Bipolar Disorders: Any self-reported cannabis use between ages 13 and 17 was associated with a doubled risk of incident psychotic and bipolar disorders. Psychotic disorders include conditions like schizophrenia, while bipolar disorder is characterized by alternating episodes of depression and mania. Psychiatric diagnoses typically followed the first report of cannabis use by an average of 1.7 to 2.3 years.
• Depressive and Anxiety Disorders: Cannabis use was also linked to an increased risk of incident depressive disorders (adjusted hazard ratio [AHR], 1.34) and anxiety disorders (AHR, 1.24). The strength of these associations decreased as adolescents aged.

  For depressive disorders, the adjusted hazard ratio (AHR) was 1.34, and for anxiety disorders, it was 1.24.

• Controlling Factors: The increased risks for these disorders persisted even after accounting for factors such as prior mental health conditions, other substance use, sex, race and ethnicity, neighborhood deprivation index, and insurance type.

Contextual Factors and Broader Implications

Researchers involved in the study noted several contextual factors and suggested potential public health implications.

• THC Potency: Modern cannabis products contain significantly higher levels of THC, with flower exceeding 20% and concentrates reaching up to 95%, in contrast to past decades.
• Demographic Patterns: The study indicated that cannabis use was more prevalent among adolescents enrolled in Medicaid and those from socioeconomically deprived neighborhoods. Researchers suggest that expanded cannabis commercialization could potentially contribute to existing mental health disparities.
• Public Health Response: Experts involved in the study suggest public health responses, including considering product potency reduction, prioritizing prevention, limiting youth exposure and marketing, and treating adolescent cannabis use as a health concern.
• Complexity of Mental Health: Mental health disorders are understood to have complex origins, involving genetics, environment, lifestyle, and life experiences.