Cannabis is often seen by many teenagers as harmless, especially as laws change and the drug becomes more widely available in some places.
However, scientists are becoming increasingly concerned about how cannabis may affect the developing brain. A large new study suggests that using cannabis during the teenage years could raise the risk of serious mental health problems later in life.
Researchers followed more than 463,000 adolescents between the ages of 13 and 17 and tracked their health into young adulthood, up to age 26. The study used medical records from routine doctor visits over several years.
The findings showed that teens who reported using cannabis in the past year were much more likely to develop psychiatric disorders later. In particular, the risk of psychotic disorders and bipolar disorder was about twice as high compared with teens who did not use cannabis. The study also found increased risks of depression and anxiety.
Psychotic disorders are severe conditions that affect how a person thinks and understands reality. They may involve hallucinations, delusions, or confusion. Bipolar disorder causes extreme mood swings between emotional highs and deep lows.
Both conditions can seriously disrupt education, relationships, and daily life. The study found that cannabis use usually happened one to two years before these mental health problems were diagnosed, suggesting that early exposure could play a role in triggering illness in vulnerable individuals.
Teenage years are a critical period for brain development. During this time, the brain is still forming connections that control thinking, emotions, and decision-making. Substances that affect the brain’s chemistry can interfere with this process.
Cannabis contains a chemical called THC, which produces the “high” feeling. In recent years, the amount of THC in cannabis products has increased dramatically. Some products now contain several times more THC than in the past, which may increase potential risks.
The researchers also found that cannabis use was more common among teens from disadvantaged backgrounds and those receiving public health insurance.
This raises concerns that increased availability and marketing of cannabis products could worsen existing health inequalities. Families in lower-income communities may have fewer resources to access mental health care or prevention programs.
Unlike some earlier research that focused only on heavy cannabis use, this study looked at any reported use within the past year. Even occasional use was linked to higher risk.
Importantly, the researchers took into account other factors such as previous mental health problems and use of alcohol or other drugs. The increased risk remained even after these factors were considered, strengthening the evidence that cannabis itself may contribute to later illness.
Experts say the findings highlight the need for better education for both parents and teenagers. Many young people may not realize that cannabis can have long-term effects on brain health, especially when used during adolescence.
Honest conversations and clear information could help teens make safer choices. Health professionals also suggest that doctors should screen for cannabis use during routine checkups and provide guidance when needed.
In reviewing the study, the large number of participants and the long follow-up period make the findings especially important. Tracking teens into adulthood allowed researchers to see how early behaviors were linked to later outcomes.
However, the study cannot prove that cannabis directly causes mental illness in every case. Other factors such as genetics, stress, and environment also play a role. More research is needed to understand exactly how cannabis interacts with these factors and which teens may be most vulnerable.
Overall, the evidence suggests that adolescent cannabis use should be treated as a serious public health concern rather than a harmless activity. Preventing early use and reducing exposure to high-potency products could help protect young people’s mental health.
As cannabis becomes more common in society, understanding its risks is essential for families, schools, and policymakers. Helping teenagers make informed decisions today may reduce the burden of mental illness in the future.
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