Parents can now add one more reason to be worried about teenage cannabis use: it may increase their children's likelihood of developing an anxiety disorder later in life.

The Study

Under the direction of Professor Louisa Degenhardt, Ph.D., of the National Drug and Alcohol Research Center at the University of New South Wales, researchers analyzed the findings of an earlier Australian study of nearly 2000 high-school students. In that study, led by Professor George Patton, PhD, at the Murdoch Children's Research Institute in Melbourne, the teen participants were followed for 13 years, beginning in 1992. They were interviewed bi-annually during their adolescent years, and at various intervals during their 20s until the age of 29.

The analysis revealed a link between frequent adolescent marijuana use and adult anxiety disorders. In fact, the results showed that teens who smoked pot daily and continued to do so throughout their 20s were three times more likely to have an anxiety disorder than their non-cannabis using peers. Those who barely smoked in their teens but became regular users in their late 20's were two and a half times as likely to develop the mental health illness.

Researchers were most surprised by the fact that adult anxiety disorders were also linked with regular adolescent marijuana use up to a full 10 years after cannabis use had stopped.

“… we need to investigate the findings further because it is highly possible that early cannabis use causes enduring mental health," said Degenhardt, noting that earlier studies had only focused on teen and early adult associations between marijuana use and mental health.

Possible Explanations

Scientists suggested that the cause of lasting damage to the brain may be triggered by cannabis use at a time when the brain is still forming.

“During the teen years, the parts of the brain that are involved in managing emotions are still developing rapidly and it is highly possible that heavy cannabis use at this sensitive point could have long lasting effects," suggested Patton.

On the other hand, it is possible that risk factors that increase the likelihood of teens using marijuana may also be increasing their likelihood of developing a mental illness later.

“This is a plausible hypothesis because social disadvantage is more common among persons who are problematic substance users and who meet criteria for common mental disorders," the study authors wrote.

Hence, while an association has been found, causation cannot yet be declared, with future studies warranted to continue exploring connections between early drug-use and future mental health outcomes.

Understanding Anxiety

The prevalence of anxiety disorders has been steadily increasing in developing nations throughout the world. The mental illness includes the following categories: post-traumatic stress disorder, social anxiety disorder, panic disorder with or without agoraphobia, generalized anxiety disorder, panic disorder and separation anxiety disorder.

Treatments generally involve psychotherapy to identify and understand thoughts, feelings and behaviors, along with medications targeting related brain mechanisms.

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