Summary: Yes, new research shows using cannabis during adolescence can increase risk of developing mental health disorders by adulthood.
Key Points:
- Recreational cannabis use is illegal for all adolescents in the U.S.
- Some states allow medical cannabis use for adolescents under strict guidelines
- Previous research indicates a minor association between adolescent cannabis use and sleep problems, lung problems, heart problems, and gastrointestinal problems
- Previous research shows mixed results for the association between adolescent cannabis use and mental health disorders
Adolescent Cannabis Use and Risk of Mental Health Disorders by Adulthood: What’s the Connection?
To address the inconsistencies in research and expand the knowledge base for understanding whether using cannabis during can adolescence increase risk of mental health disorders by adulthood, a group of researchers designed the study “Adolescent Cannabis Use and Risk of Psychotic, Bipolar, Depressive, and Anxiety Disorders” around this primary research question:
“Is adolescent cannabis use associated with an increased risk of developing psychiatric disorders by young adulthood?”
Earlier research cited by the study authors shows cannabis use at any age can increase risk for:
- Any psychiatric disorder
- Highest risk for development of psychotic disorders.
Research also shows cannabis use during adolescence can increase risk of mental health disorders during adulthood, including:
- Schizophrenia
- Othe psychotic disorders
- Hypomanic episodes
- Bipolar disorder
In addition, previous evidence indicates:
- Moderate evidence for association between adolescent cannabis use and adult depression
- Weak and inconsistent evidence for association between adolescent cannabis use and adult anxiety
However, with regards to mental health disorders with psychotic features, such as schizophrenia, at least one large-scale study defined the association between adolescent cannabis use and increased risk of psychotic disorders as inconclusive, reporting the following:
“We did not observe evidence for the contributing risk hypothesis in the primary analyses, as psychosis spectrum symptoms generally did not increase after cannabis initiation. However, mixed evidence for the contributing risk hypothesis was observed in sensitivity analyses.”
In the new study we discuss above, researchers hope to clarify any connection between using cannabis during adolescence and increased risk of developing mental health disorders by adulthood.
Let’s take a look at how they conducted the study.
A Large-Scale Analysis of Adolescent and Young Adult Health Records in Northern California
The research team collected records for a total of 463,598 adolescent members of Kaiser Permanente Northern California (KPNC), aged 13 to 17. All participants completed The Teen Well-Check Questionnaire (TWCQ) to account for confounding disease or illness at baseline and annually between 2016 and 2023. Researchers excluded participants with previous alcohol or substance use from their initial analysis, and adjusted for the presence of psychiatric disorders for the second, adjusted analysis.
To assess cannabis use, each participants answered the question “During the past year, did you use marijuana? (yes/no).”
To assess the development of psychiatric disorders, researchers accessed and analyzed anonymized patient health records provided by KPNC. Disorders of primary interest included:
- Psychotic disorders
- Bipolar disorders
- Depressive disorders
- Anxiety disorders
Before we share their baseline data on the study, let’s review the latest data on cannabis use among adolescents as reported in the 2024 National Survey on Drug Use and Health (2024 NSDUH):
Past Year/Past Month/First Cannabis Use, Adolescents 12-17, 2024
- Past Year: 10.4% / 2.7 million
- Past Month: 6.05 / 1.6 million
- Diagnosed disordered cannabis use: 6.6% / 1.2 million
- Used for first time: 3.5% / 912,00
As the data shows, millions of adolescents nationwide use cannabis every year, with nearly a million using cannabis for the first time in 2024. That data gives us perspective and offers context for the study results.
Now let’s look at the baseline data – i.e. at the start of the study – on cannabis use as reported by the research team.
Past-Year Cannabis Use at Baseline
Total 13-17:
- 5.7%
By Gender:
- Female: 51.6%
- Male: 48.3%
Race/Ethnicity:
- White: 40.7%
- Hispanic: 32.1%
- Black: 10.9%
- Asian: 7.2%
- Other or multiracial: 4.1%
By Age:
- 13: 6.1%
- 14: 15.6%
- 15: 20.1%
- 16: 26.6%
- 17: 31.6%
Other baseline metrics:
- Past-year alcohol use: 6.8%
- Among teens with past-year cannabis use: 64.3%
- Past-year any other substance: 2.1%
- Among teens with past-year cannabis use: 22.7%
- Diagnosis of behavioral disorder: 4.2%
- Among teens with past-year cannabis use: 8.7%
We’ll discuss this baseline data below.
Cannabis, Adolescents, and Mental Health Disorders by Adulthood
Findings of note in that initial baseline data indicate that more females reported higher rates of cannabis use than males, white adolescents reported the highest rates of cannabis use than any other racial/ethnic group, and that the youngest adolescents reported far lower rates of cannabis use than older adolescents.
The data on alcohol use, any substance use, and diagnosis of behavioral disorders is informative, but not included in the primary analytic goals defined by the research team.
With all that information in mind, including the fact that baseline cannabis use rates appeared lower than reliable national estimates, let’s take a look at what they found at follow up. Did using cannabis during adolescence increase risk of developing mental health disorders by adulthood?
Presence of Psychiatric Disorders: Risk of Developing Disorder by Age 18
(Adjusted for alcohol use, other substance use, and behavioral disorders)
- Psychotic disorder:
- HR: 2.19
- The risk of developing a psychotic disorder by age 18 is 2.19 times more likely for adolescents with past-year cannabis use, compared to adolescents with no cannabis use
- Bipolar disorder:
- HR: 2.10
- The risk of developing bipolar disorder by age 18 is 2.10 times more likely for adolescents with past-year cannabis use, compared to adolescents with no cannabis use
- Depressive disorder:
- HR: 1.34
- The risk of developing a depressive disorder by age 18 is 1.34 times more likely for adolescents with past-year cannabis use, compared to adolescents with no cannabis use
- Anxiety disorder:
- HR: 1.24
- The risk of developing an anxiety disorder by age 18 is 1.24 times more likely for adolescents with past-year cannabis use, compared to adolescents with no cannabis use
Those are the initial outcomes: cannabis use during adolescence increased risk of developing psychotic disorders, bipolar disorder, depressive disorder, and anxiety disorder before age 18, with the weakest association reported for anxiety disorders.
Additional Analysis: Excluding Prior and Subsequent Mental Health Diagnoses
Next, the research team adjusted the results to account for the presence of other mental health disorders present at baseline, thereby isolating the effect to cannabis alone. Here’s what they found:
- Psychotic disorder:
- HR: 1.92
- Bipolar disorder:
- HR: 1.73
- Depressive disorder:
- HR: 1.33
- Anxiety disorder:
- HR: 1.19
The results were similar, but the strength of associations decreased by a small margin. Next, the research team adjusted the results to account for the presence of other mental health disorders at any time before or after baseline. Here’s what they found:
- Psychotic disorder:
- HR: 1.99
- Bipolar disorder:
- HR: 2.00
- Depressive disorder:
- HR: 1.37
- Anxiety disorder:
- HR: 1.22
The results were also similar, but like the previous adjustment, the strength of associations decreased by a small margin. The research team then analyzed the risk of developing depression and anxiety by age group, excluding participants with previous mental health diagnoses.
For depressive disorder, by age (HR):
- 13 to 15: 1.78
- 16 to 17: 1.35
- 18 to 20: 1.21
- 21 to 25: 0.97 / not statistically significant
For anxiety disorder, by age (HR):
- 13 to 15: 1.47
- 16 to 17: 1.24
- 18 to 20: 1.24
- 21 to 25: 0.95 / not statistically significant
That set of data is illuminating. The risk of depressive and anxiety disorders associated with cannabis use decreases by age, which confirms the previously reported heightened vulnerability among early teens for the negative effects of substance use.
Finally, the research team analyzed the data to determine the mean length of time it took for each type of disorder to appear after first cannabis use.
Mean Time to Onset of Psychiatric Disorder After Initiation of Cannabis Use
- Bipolar disorder: 2.3 years
- Psychotic disorders: 2.0 years
- Anxiety disorder: 1.9 years
- Depressive disorder: 1.7 years
This data applies only to participants who used cannabis and developed one of the disorders of interest. These figures do not mean, for instance, that if an adolescent uses cannabis they will develop a psychotic disorder within two years.
We’ll discuss these outcomes further, below.
Summing Up the Data on Using Cannabis During Adolescence and Increase of Risk of Developing Mental Health Disorders by Adulthood
What the last set of data shows is that among that group of teens – which is a large group, allowing us to generalize about the topic – the disorders appeared, in most cases, within two to two and a half years of initiation of cannabis use. This aligns with the data on depression and anxiety, which show the strength of the association between cannabis use and mental health disorders decreases as age increases, fading to insignificance by 21 to 25 years of age.
Here’s how the research team describe their results:
“We found that adolescent cannabis use was associated with an increased risk of multiple psychiatric disorders by early adulthood. Associations were stronger for psychotic and bipolar disorders. Together, these results are consistent with cannabis being a risk factor for or exacerbating the risk of psychiatric disorders rather than only resulting from preexisting psychiatric conditions.”
The researchers then go on to suggest that, given the recent trend toward the legalization of recreational cannabis nationwide, their findings take on significance for parents and professionals working with adolescents:
“These findings reinforce the need for early prevention efforts, stronger public health messaging, and policy strategies that limit youth exposure in the context of expanding cannabis legalization.”
We think that’s an excellent takeaway from both the study and this article. We’ll end by reiterating the data on the association between age of initiation of cannabis use and subsequent mental health problems. This is something parents can tell their teens:
