Global attitudes towards cannabis have changed, with an increasing focus on exploring its potential medicinal uses and legalizing it. Eight countries, including Canada, Uruguay, Mexico and Thailand, and 22 states in the US have legalized recreational marijuana, and nearly 50 countries have legalized it for medicinal use. Many other countries are now pushing their laws in that direction. (Also Read: What should be the ideal screen time for teenage girls? Answers from experts)
But like tobacco and alcohol, legalization means the drug is no longer harmful.
Marijuana is also the most used substance among teenagers worldwide. According to researchers at Columbia University in New York, in the US, more than 2.5 million teenagers use cannabis informally, and cannabis use among young people has increased in recent decades.
Hence the trend of legalization and medicinal use has raised concerns about potential health risks, especially among adolescents.
A developing brain
Although it can be difficult to tell when adolescence stops, it is clear that it is a time period that comes with many biological changes, including changes in the brain.
Those changes make it more difficult to understand how cannabis might affect the brains of teenagers.
According to the US National Institute of Mental Health, during adolescence, the brain continues to develop until the mid-20s.
During this time, there is great development and fine-tuning in areas of the brain related to handling emotions, coping with stress, reward and motivation, decision making, thinking before acting, controlling impulses and reasoning, to name just a few. There is also an increase in white matter and a decrease in gray matter during adolescence, which helps different areas of the brain communicate quickly and efficiently.
It’s a tough life for teenagers. Not only do they undergo major changes in their bodies, but they often struggle with issues like identity, social pressure, getting good grades, family dynamics and more.
All of these changes and pressures can make teens more likely to develop mental health problems like anxiety and depression, and they may use substances like marijuana to cope, according to the U.S. Substance Abuse and Mental Health Services Administration. The problem is that marijuana use can make those mental health conditions worse in the long run.
Because the brain is still developing at this stage, it is particularly vulnerable to alcohol, tobacco, marijuana, and other drugs that act on it. According to the American Academy of Child and Adolescent Psychiatry, these substances have been shown to alter or delay certain developments that normally occur during adolescence.
In the case of cannabis, there is growing evidence that it modifies the adolescent brain.
Evidence on cannabis and depression
Marijuana use has been linked to difficulty thinking and solving problems, memory and learning, poor coordination and difficulty concentrating, according to the US Centers for Disease Control and Prevention (CDC). It is not yet clear whether these problems persist after cessation of cannabis use.
Research has also shown a link between cannabis use and mental health problems such as anxiety and depression. People who use cannabis are also more likely to have psychotic episodes.
A study published in JAMA, the journal of the American Medical Association, earlier this month looked at teenagers who had used cannabis occasionally in the last 12 months. The study analyzed the responses of nearly 70,000 adolescents to the 2019 National Survey on Drug Use and Health.
The study found that compared to non-users, those who used marijuana but did not meet criteria for addiction reported 2 to 4 times more mental health problems such as depression, suicidal thoughts, slow thinking and difficulty concentrating.
This may suggest a link between marijuana use and mental health problems, but it is not yet clear whether one directly causes the other.
Another recent study published in JAMA Psychiatry found that adolescent marijuana use was associated with an increased risk of developing depression and suicidal thoughts later in life.
However, a 2022 study published in the Journal of Psychopharmacology found that adolescents who use cannabis are no more likely to develop mental health problems such as depression or anxiety than adults who use cannabis. Only cannabis-addicted adolescents had poorer mental health.
What causes cannabis?
Correlation does not equate causation and “which came first, the egg or the chicken?” As is the case, it is difficult to say whether adolescent cannabis use is the reason for the high association with depression and other mental health problems. Teens with these problems are more likely to use cannabis.
A 2020 study published in Frontiers of Psychology reviewed the evidence on cannabis and the adolescent brain and concluded that because many of the available studies, so-called cross-sectional studies, are designed, we do not know much about the nature. The relationship between cannabis use and mental health.
Cross-sectional studies look at different groups of people at a specific point in time. The objective is to gather information about a particular topic by collecting data from a diverse group of people at once. Researchers then analyze the data and try to find patterns or relationships, but they can’t establish why.
Frontiers in Psychology also emphasized that it is possible that cannabis use and mental health problems may be caused by other factors, such as the sensitivity of adolescents to stress and anxiety, as mentioned earlier.
To find out whether cannabis causes mental health problems in teenagers, more research is needed.
Edited by: Carla Bleiker