For many young people, cannabis is seen as a normal part of social life. Some use it to relax after a stressful day, while others believe it is safer than alcohol or other drugs.
The growing legalization of cannabis in some countries has also led many people to think that it carries little risk. Yet scientists continue to uncover evidence suggesting that regular cannabis use may have important consequences for mental health.
A large international review led by researchers at the University of Queensland has highlighted one of the biggest concerns. The study found that young people who use cannabis every day may be up to four times more likely to develop psychosis than people who do not use the drug.
Psychosis is not simply feeling worried or sad. It is a serious condition that changes the way people think and perceive reality. Individuals with psychosis may hear voices, become confused, or strongly believe things that are not true. These symptoms can be frightening and can seriously affect education, work, relationships, and everyday functioning.
The researchers examined evidence from 17 earlier studies that investigated links between cannabis use and mental health conditions, including psychosis, bipolar disorder, depression, and anxiety.
After reviewing all of the available evidence, they concluded that the relationship between daily cannabis use and psychosis was the clearest and most reliable finding.
According to Associate Professor Janni Leung from the University of Queensland’s National Centre for Youth Substance Use Research, young people are especially vulnerable because their brains are still developing. The human brain continues to mature well into early adulthood.
During these years, the brain undergoes major changes that help people improve decision-making, emotional control, and thinking skills. Exposure to substances that affect brain chemistry during this period may have long-lasting effects.
The researchers also found that about one-third of people aged 15 to 25 who used cannabis every day or almost every day developed cannabis use disorder.
This means they found it difficult to control their cannabis use even when it created problems in their lives. The condition can interfere with school performance, employment, relationships, and physical and mental health.
The review also suggested that frequent cannabis use may contribute to worsening symptoms in people with bipolar disorder. Bipolar disorder causes periods of unusually elevated mood and periods of depression. The findings indicate that cannabis may make these symptoms more difficult to manage.
The evidence linking cannabis to depression and anxiety was less consistent. However, several studies suggested that people experienced improvements in their mental health after reducing their cannabis use or stopping completely. This observation indicates that cannabis may be contributing to symptoms in at least some users.
The researchers also participated in a second review published in The Lancet Psychiatry. That study found no clear evidence that medicinal cannabis effectively treats anxiety, depression, or sleep problems. The findings suggest that cannabis should not replace treatments that already have stronger scientific support.
The researchers believe healthcare professionals should routinely ask about cannabis use when assessing mental health. They also recommend providing integrated care for people who have both mental health problems and cannabis use disorder because treating one condition while ignoring the other may not be effective.
The review provides strong evidence that heavy cannabis use and psychosis are closely linked in young people. Although the study cannot prove that cannabis directly causes psychosis in every case, the repeated findings across many studies make the relationship highly concerning.
The review also highlights an important public health issue because both cannabis use and mental health disorders often begin during adolescence and early adulthood.
These findings suggest that prevention efforts should focus particularly on young people and that public discussions about cannabis need to include its potential mental health risks as well as any possible benefits.
If you care about smoking, please read studies about smoking may increase heart disease risk by 200% and e-cigarette smoke may cause lung cancer and bladder disease.
For more health information, please see recent studies about the cause of weight gain after smoking cessation, and results showing smoking may cause white scars on the brain.
Source: University of Queensland.
