Marijuana has been increasingly destigmatized in recent years and several states have made it legal for recreational use. For many, this legalization creates a perception of safety. In fact, the 2014 US National Survey on Drug Use and Health found only 33% of Americans perceived smoking marijuana once or twice week as “greatly harmful” compared to 51% in 2002 (Shen). Is marijuana really as safe as many people have come to believe? A study of 108 young adults from the Michigan Longitudinal Study attempts to investigate the alleged “harmlessness” of marijuana by focusing on the long term consequences of sustained marijuana use.
Take a moment and think about how you feel when you eat a piece of candy, have sex, or win money from a bet. You likely experience happiness, satisfaction, and excitement—all of which can be attributed to the reward circuitry in your brain. When presented with rewarding stimuli the ventral tegmental area (VTA) releases dopamine into the nucleus accumbens (NAc). Marijuana activates this same reward circuity that allows you to enjoy food, sex and money and creates an “artificially” rewarding experience. This begs the question: could sustained marijuana use, which manipulates the body’s natural reward circuits, affect the way in which people process non-drug rewards such as food and sex? To examine the impact long term marijuana use has on the brain’s reward circuitry, researchers at the Michigan Longitudinal Study used MRI machines to scan the brains of over one-hundred long-term marijuana users as they performed a specific task: pressing a button when a target appeared on a screen in order to get monetary rewards. The result? Long-term users had a decrease in NAc activation when anticipating monetary rewards.
So what does this mean for the recreational marijuana user? Should you pass on the next round of puff, puff, pass? The study, aimed mainly at long term users, seems to say that the occasional partaker can breathe easy. As for long term users, it may already be too late. Those rewarding emotions that one once felt when eating a big slice of cake may now be diminished, “overshadowed” by marijuana’s artificially rewarding experience that comes from using marijuana. This is not to say that you won’t still find the cake rewarding; you might have once given a cake 100 “rewarding points” whereas after sustained marijuana use you may only give the cake 70 “rewarding points”. This loss of satisfaction/reward could lead long-term marijuana users to increase the frequency of use or even to seek out more dangerous substances in an attempt to chase the feelings they may have once experienced from non-drug rewards.
Marijuana is increasingly viewed as less dangerous and yet, at the same time, is more accessible. This is a dangerous combination as many users are unaware of the potentially damaging effects of long-term marijuana use. The rewarding experience that occurs when using marijuana may eventually jeopardize a person’s ability to experience reward from other non-drug “rewarding” stimuli such as food, sex, and money.
Bibliography: Martz, M. E., Trucco, E. M., Cope, L. M., Hardee, J. E., Jester, J. M., Zucker, R. A., & Heitzeg, M. M. (2016). Association of Marijuana Use With Blunted Nucleus Accumbens Response to Reward Anticipation. JAMA Psychiatry.
Shen, Lucinda. “More Americans Are Smoking Weed on a Daily Basis.” More Americans Are Using Marijuana On a Daily Basis | Fortune.com. Fortune, 01 Sept. 2016. Web. 09 Mar. 2017.