Global marijuana use is rising, driven in part by expanding legalization and accessibility across the United States. [1] While cannabis use has long been linked to mental health disorders, a new study has now highlighted the heightened risk cannabis use poses to adolescents. [2][3] Given that cannabis is the most commonly used illicit substance by adolescents in the United States, this is of significant concern. [2]
Key findings: What the study found
This was a large cohort study that tracked 463,396 adolescents from the United States from ages 13 to 17 and followed them until their 20s. [2][3] The study was conducted by accessing the medical records of the individuals from 2016 to 2023. [2][3] It found that adolescents who reported cannabis use were more likely to develop a range of mental health disorders. [2][3] Specifically, teens who used cannabis were around twice as likely to develop psychotic and bipolar disorders. [2][3]
Of the total sample size, 5.7% reported cannabis use within the past year. [3] Cannabis use was seen on average 1.7 to 2.3 years before diagnosis of a psychiatric disorder. [2] Although cannabis use was most strongly associated with the development of psychotic and bipolar disorders, there was also a rise in depressive and anxiety disorders. [3]
Why teen cannabis use might affect mental health
Adolescence is a vital period of brain development. During these years, the brain undergoes significant changes that can naturally drive increased risk-taking behavior. [4] This development continues until approximately age 25, a critical window for long-term brain function. Because the brain is still maturing, it's also more vulnerable to external factors during this time, making adolescents more susceptible to developing negative coping skills and dysfunctional behavior patterns, including substance use disorder. [4][5]
Tetrahydrocannabinol (THC), the main psychoactive component in cannabis, plays a central role in this risk. [6] Adolescents exposed to THC tend to show reduced cognitive growth, including impairments in memory and attention. [7] Over time, this disruption can contribute to the development of a range of mental health disorders. [2]
Limitations and what the study doesn’t prove
Although this was a large study, it has several limitations. [3] The sample consists of adolescents screened for cannabis use during standard pediatric care in a large Northern California health system. [3] This may limit generalizability to the wider population, including those who are uninsured and those living in states where cannabis remains illegal. [3]
Additionally, cannabis use was likely to be under-reported. Other research suggests the prevalence of cannabis use in teenagers is much higher than the 5.7% reported in this study. [8] Although the study notably demonstrates that cannabis use preceded an increase in psychiatric diagnoses, it does not prove that cannabis caused these outcomes. [3] There may be other contributing factors, such as adverse childhood experiences and genetics, that were not taken into account. [3]
Why potency and access may be making this issue bigger
Increased THC concentrations, cannabis legalization, and aggressive marketing are all contributing to normalizing cannabis use, making the issue much larger. [2] One study found the average strength of cannabis products had increased from 10 to 14%, with other strains thought to be even more potent. [9] Cannabis concentrates used for vaping have also become more popular, and have a strength of at least 50% cannabinoid. [10]
Wider legalization has also changed how teens encounter cannabis, with products today being more varied and easier to purchase. [2] They are also often marketed in ways that appeal to younger users, such as exciting flavors or interesting vape pens. As access to cannabis expands, cannabis use may start earlier and continue to become more normalized, both of which could exacerbate the mental health risks outlined in this study. [2][3]
Warning signs parents should not ignore
Recognizing a change in a teen's mental state isn't always easy. However, certain changes are worth paying closer attention to, which could indicate substance use or mental health problems. These include:
- Withdrawal from friends or family.
- Loss of interest in activities they once enjoyed.
- Noticeable drop in academic performance.
- Changes in sleep or appetite.
- Unexplained irritability, paranoia, and other changes in mood or personality.
More physical signs could also indicate acute cannabis use, such as red eyes or an unusual odor. Because this study found that cannabis use often preceded psychiatric diagnosis by one to two years, acting on early behavioral changes may help to prevent the psychiatric condition from developing. [2]
How to talk to a teen about cannabis use
Talking to a teen about cannabis can feel awkward. Approaching the conversation openly and honestly is the best way to address cannabis use. Phrasing questions with curiosity rather than accusation is likely to keep the teen more engaged and less likely to shut the conversation down. This could include asking open-ended questions about what they've seen or heard from peers.
Once you have had an open conversation about cannabis use, it can then become easier to discuss the risks associated with it and why the teen should avoid it. Conversations could include discussing healthy habits, such as sufficient sleep and exercise, and how the teen can be supported with this.
Prevention and early intervention
Prevention and early intervention are vital to tackling teen cannabis use. Prevention tools, such as education and structured activities around substance use and mental health, can be delivered both in school and at home. When substance use is disclosed, early intervention can help to prevent it from becoming a more chronic concern.
Healthcare professionals who routinely screen for cannabis use are more likely to discover use before it escalates or before mental health symptoms become apparent. Early conversations with a healthcare provider can also help normalize help-seeking, making teens more likely to speak up if concerns arise later. Parents can help support this by having a trusted relationship with their teen and facilitating open conversations about substance use without judgment. Monitoring for the warning signs can also help indicate when professional support may be required.
When to seek professional help
If a teen is using cannabis regularly, or if warning signs of a mental health condition appear alongside cannabis use, it's worth seeking professional help. If their mental health seems to be deteriorating, or if any signs of psychosis are present, such as hallucinations or delusions, this help should be sought urgently.
Early treatment for both substance use and any emerging mental health conditions tends to lead to better long-term outcomes. The mainstay of treatment for cannabis use is behavioral therapies, such as Cognitive Behavioral Therapy (CBT), which is effective in this group. [11] Depending on the severity of the symptoms, a more intensive inpatient stay could be beneficial.
Final thought
This study adds to a growing amount of evidence highlighting that adolescence is a particularly vulnerable window for cannabis-related harm. While it doesn't prove that cannabis directly causes psychiatric disorders, the strength and consistency of this association is concerning. As cannabis becomes more potent and more accessible, staying informed and engaged is vital for parents to help protect their teens' long-term mental health. If you, or someone you know, is struggling with cannabis use, please reach out to a healthcare professional.
