Medical marijuana legalization does not increase use in adolescents

16 Jun

Many have expressed concern that the legalization of marijuana for medical purposes makes the drug both more accessible and acceptable to teenagers. However, a new study states that there is no evidence that such legislation leads to increased use in adolescents.

Two people smoking joints.
The effect that medical marijuana legislation has on adolescent marijuana use has been the subject of heated discussion.

The study, published in The Lancet Psychiatry, involves an analysis of data for more than one million American adolescents across the US from 1991-2014.

“Our findings provide the strongest evidence to date that marijuana use by teenagers does not increase after a state legalizes medical marijuana,” states study author Dr. Deborah Hasin, professor of epidemiology at Columbia University Medical Center in New York.

So far, a total of 23 US states and the District of Columbia has passed legislation that allows for the legal use of marijuana for medical purposes. Here, the drug can often be prescribed for pain relief and the treatment of other symptoms such as nausea and loss of appetite.

However, a number of harmful effects are associated with adolescent use of the drug and particularly with regular use. These include short-term impairments in memory and co-ordination and, in the long-term, risks of psychiatric symptoms, cognitive impairments and substance abuse.

Marijuana is the most commonly used illicit drug in the world, with an estimated 19.8 million Americans reported to use it every month. Even the youngest children are known to consume it; a recent study found that marijuana exposure among children younger than 6 rose by 147.5% from 2006-13.

The effect that medical marijuana laws have on adolescent marijuana use is hotly debated. Some believe that such laws increase adolescent use while others state that the laws either have no effect or discourage use.

No change in adolescent marijuana use after marijuana legislation enacted

To investigate, the researchers analyzed data obtained from the national Monitoring the Future survey, involving more than one million students aged 13-18 between 1991 and 2014. During this time, 21 of the 48 contiguous states passed laws allowing for the legal use of medical marijuana.

The researchers found that although marijuana use among adolescents was higher in the states that legalized medical marijuana than in those that did not, the prevalence of marijuana use did not change after these laws were introduced.

As these differences in marijuana use between states existed prior to the introduction of medical marijuana legalization, the researchers suggest there may be other differences in common factors such as norms surrounding marijuana use that warrant further investigation.

“Because early adolescent use of marijuana can lead to many long-term harmful outcomes, identifying the factors that actually play a role in adolescent use should be a high research priority,” explains Dr. Hasin.

The researchers also suggest that their findings may not be generalizable to states that are considering but have yet to pass medical marijuana laws. According to the researchers, these states tend to have a lower prevalence of adolescent marijuana use and so the impact of new legislation could differ.

In a linked comment, Dr. Kevin Hill from the Division of Alcohol and Drug Abuse, McLean Hospital, Belmont, MA, writes that the study illustrates the importance of using the results of rigorous scientific research to shape health policies.

“[The] growing body of research that includes this study suggests that medical marijuana laws do not increase adolescent use, and future decisions that states make about whether or not to enact medical marijuana laws should be at least partly guided by this evidence,” he states.

Previously, Medical News Today reported on a study that found success in preventing, reducing or delaying cannabis use among at-risk teenagers with cognitive behavioral sessions.

Written by James McIntosh