Cannabis use before age15 is linked to physical and mental health issues : Shots

The adolescent brain is still developing, and regular cannabis use can disrupt healthy neural development.

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Sara Ruiz//iStockphoto/Getty Images

Adolescents who start using cannabis before the age of 15 are more likely to use it frequently later in life. They are also more likely to develop mental and physical health problems as adults than their peers who did not use drugs as adolescents.

These are the findings of a new study conducted Open JAMA Network.

“This further strengthens the argument that cannabis use during adolescence negatively affects [health] trajectories of those who use it,” says psychiatrist Dr. Ryan Sultan of Columbia University, who was not involved in the new research.

The new study used data from the Quebec Longitudinal Study of Child Development. Researchers in Montreal, Canada, followed more than 1,500 children from birth to adulthood to understand the factors that influence their development and health. Among the different aspects of children’s lives and habits that scientists have recorded is the use of cannabis between the ages of 12 and 17.

Researchers found that a majority of adolescents – 60% – had not used cannabis as a teenager. Of the remaining 40%, half started using cannabis in their late teens, and by age 17, they were using it rarely – less than once a month. The remaining 20% ​​started using marijuana before age 15, and by age 17, they were using it at least once a month.

The latter group was more likely to seek health care as adults for mental and physical health problems than those who did not use drugs as adolescents.

“The risk is concentrated in those who start early and use frequently,” explains psychologist and lead author of the study Massimiliano Orri of McGill University.

Early and frequent cannabis users were 51% more likely to seek care for mental health issues in young adulthood than those who did not use cannabis. And this risk was calculated after taking into account a series of confounding factors known to influence health, such as bullying or lack of parental involvement.

Similarly, early and frequent cannabis users were 86% more likely to need care for physical health reasons.

“We have indications that respiratory problems were the most frequently reported, as well as accidents and unintentional injuries,” says Orri.

These physical health problems could be linked to cannabis intoxication, but could also be due to withdrawal symptoms, Orri and colleagues write in the journal.

“It certainly makes sense,” says psychologist Krista Lisdahl of the University of Wisconsin-Milwaukee, who also studies adolescent brain development and health but was not involved in the new research. “It’s alarming and it’s something that we really need to monitor more closely here in the United States as well.”

A key strength of the study is that Orri and his colleagues controlled for many confounding factors, Lisdahl adds.

“There are many factors related to physical health and mental health,” says Lisdahl. And the new study controlled for many of them, including “family, parental conflict and parenting style, and parental monitoring of adolescents.” They also looked at individual-level factors such as social skills, peer relationships and whether a child was victimized by peers.

Previous studies have also linked adolescent cannabis use to a higher risk of developing mental health symptoms.

Sultan’s recent research found a two to four times higher likelihood of developing psychiatric disorders among adolescents who use cannabis recreationally than among adolescents who do not use cannabis at all. Other studies have suggested a link between early cannabis use and psychosis in young people. He and his colleagues also found a higher risk of other impacts such as poor grades and truancy.

“The adolescent brain continues to develop very dynamically during the adolescent period and into adulthood,” says Lisdahl. “Regularly consuming something like cannabis during this time could disrupt this healthy neural development, particularly in areas of the brain related to executive functioning, such as problem solving, planning, perhaps controlling other types of behaviors and impulses, but also emotion regulation,” she says.

Take for example an anxiety-prone teenager who turns to cannabis to feel less anxious, Sultan says. “If you start doing it regularly, it’s now your method of managing your anxiety,” he says. “It becomes your coping ability and you become atrophied in any ability to deal with it in any other way.”

The same thing can happen to someone who uses cannabis to manage their mood, he adds.

So, for someone who is already predisposed to certain mental health symptoms, starting to use cannabis as a teenager may increase the likelihood that these symptoms will worsen over time and develop into mental health disorders.

For all these reasons, Sultan – a child and adolescent psychiatrist – says he often talks to teenagers and parents about delaying cannabis use until age 25, to minimize the risk of health and behavioral problems later in life.