Is marijuana use increasing the burden of mental illness?

Written by Sonia Parikh, M.D.

Public perception of marijuana has shifted significantly over the past decade. Historical concerns about “Reefer Madness” from marijuana use have evolved into today’s near glamorization of the substance. Opinion polls indicate that public support for the legalization of marijuana is currently at an all-time high. Moreover, the substance is now legal in some form or decriminalized in more than half of the United States. Just a couple of weeks ago, The New York Times boldly suggested that the federal government should legalize marijuana use on a national level.

There is, unfortunately, a strong trend toward euphemizing a substance that may have long-term negative effects on our society as a whole. Don’t get me wrong – as a physician, I know that marijuana can have some benefits. It has proven medicinal value in specific illness states, such as relieving appetite loss in AIDS patients and pain in cancer patients.
However, prevalence statistics indicate that adolescents are exposed to and regularly using marijuana at rates higher than any other age group.

Individuals ages 12-17 are dependent on marijuana at a ratio of nearly 2:1 when compared with adults 35 and older. Moreover, adolescents’ opinion of marijuana’s harmfulness is decreasing, which foreshadows increases in future use. The legalization of recreational marijuana would make the drug all that more accessible and socially acceptable, so it is reasonable to predict that teen use would further increase as policy shifts toward legalization.

Why is this important? Because the science to date clearly indicates that early marijuana use can alter normal adolescent brain development and increase an adult’s susceptibility to psychiatric disease and addiction. Marijuana’s primary active ingredient, 9-tetrahydrocannabinol, infringes on the brain’s endocannabinoid system, which is critical to brain development both pre- and postnatally. This may predispose young users to later psychiatric illness and addiction. The studies that follow people across time clearly support this association.

There is a higher incidence of anxiety and depressive states and suicidal tendencies in people who begin using marijuana regularly during adolescence (Frontiers in Psychiatry, October 2013).
There is also a roughly twofold increased risk of developing schizophrenia-related disorders in young marijuana users, especially in those who have genetic vulnerability to schizophrenia.
Research reveals that 1 in 6 teens who use marijuana will become addicted. Multiple studies demonstrate that early marijuana use predisposes individuals to abuse a range of other illicit drugs as adults (New England Journal of Medicine, June 2014).

Among other explanations for this, marijuana exposure during adolescence may alter the reward pathways in the brain and prime it for enhanced responses to other drugs, increasing the likelihood for these later addictions.
Psychiatric diseases are complex, with numerous factors contributing to susceptibility and disease expression. It’s hard to say which young individuals using marijuana will progress to psychiatric illness or addiction later in life, as multiple factors are usually at play in the transition from early marijuana exposure to subsequent mental illness.

Given all of the unknowns, it is worrisome that increasing numbers of states in the U.S. are legalizing marijuana for recreational use. The longstanding societal impact of such policy change may be more ominous and problematic than originally thought. It is important that we educate ourselves on the mental health impacts of early marijuana use and communicate our knowledge to the young people in our lives, as their futures may depend on it.