Statewide Marijuana Legalization Leads to Harmful Use Patterns Among Young Adults

Person walking by group
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The last 25 years have seen a gradual increase in marijuana decriminalization, legalization for medicinal use, and legalization for recreational use. Since 2012, 15 states have legalized cannabis for recreational use. Since 1996, 29 states have legalized cannabis for medicinal use or have decriminalized the substance. At the time of this writing, only 6 states remain where marijuana is fully illegal.

Marijuana use is particularly detrimental to young adults. Studies show that as legalization increases, more young people use marijuana. That sets the stage for long-term harm, more car accidents among youth, future health problems, impaired thinking, reduced memory, inhibited learning function, and stunted brain development.

Increasing Marijuana Legalization Leads to More Use Among Young People

There’s a relatively conclusive body of information indicating that, as states legalize marijuana, more young people within those states begin to experiment with the substance. When a state legalizes, the absence of criminality in marijuana, the lack of legal repercussions, and increased ease of access all serve to make young people more comfortable with the thought of using. Furthermore, as states legalize, young people perceive cannabis products as less risky, given that they are now legal and accessible.

A December 2020 study published in the American Journal on Addictions was one of many that brought these issues to light. The researchers surveyed 1,097 young adults ages 21 and older living in Los Angeles County. The young adults were surveyed before licensed recreational cannabis outlets were opened and after. According to the study results, more of the 1,097 young people had used cannabis after the cannabis outlets opened than before, indicating that legality and availability both play a role in incentivizing young people to experiment with cannabis.

For each additional licensed marijuana outlet, there was an expected 0.7% increase in the odds of using marijuana in the past month...
Marijuana outlet
Photo by joebelanger/

The researchers were able to break down exactly how likely an LA youth was to use cannabis based on their proximity to cannabis retail outlets. A Rand Corporation article that covered the research states, “For each additional licensed marijuana outlet, there was an expected 0.7% increase in the odds of using marijuana in the past month. For example, there was an approximate 10% increase in the odds of using marijuana for someone with 14 licensed outlets within a 4-mile radius compared with someone with no outlets.”

The LA-based study referenced above is not the only one of its kind. A November 2019 research paper laid out the changes in young adult marijuana use from 2008 to 2016, a timeline in which a few states legalized cannabis for recreational use and many more legalized for medicinal use. This particular study surveyed 505,796 young people, comparing marijuana use before and after legalization. The proportion of participants responding that they did use marijuana increased from 2.18% before legalization to 2.72% after legalization.

Dr. Magdalena Cerdá, Associate Professor and Director of the Center for Opioid Epidemiology and Policy at NYU Langone Health, was the lead study author. She commented on the findings, saying that “There are, indeed, important social benefits that legalizing marijuana can provide, particularly around issues of equity in criminal justice. Our findings suggest that as more states move toward legalizing marijuana for recreational use, we also need to think about investing in substance use prevention and treatment to prevent unintended harms—particularly among adolescents.”

Another study author, Dr. Silvia S. Martins, Associate Professor of Epidemiology at Columbia University Mailman School of Public Health, also provided valuable comments. “Cannabis use disorder in adolescence is associated with long-term adverse health, economic and social consequences. Given our findings on problematic use across age groups, legalization efforts should coincide with prevention and treatment. The general public should be informed about both benefits and potential harms of marijuana products to make informed decisions.”

Marijuana has a Uniquely Harmful Effect on Young People

The National Institute on Drug Abuse has repeatedly reported on the adverse effect of marijuana use on young people. Specifically, NIDA reports that cannabis use can have particularly damaging, even permanent results in one’s youth. When a teenager or young adult uses marijuana, it can impair thinking, reduce memory, inhibit learning function, and stunt brain development. NIDA has cited multiple studies on this, strongly encouraging young people to stay away from marijuana in doing so.

A thorough research paper published by Pediatrics indicated considerable harm and risk for long-term consequences when young people use marijuana. Quoting authors Ladegard, Thurstone, and Rylander, Various states have legalized marijuana for medical purposes and/or decriminalized recreational marijuana use. These changes coincide with a decrease in perceived harmfulness of the drug and an increase in its use among youth. This change is of critical concern because of the potential harmful impact of marijuana exposure on adolescents. Marijuana use has been associated with several adverse mental health outcomes, including increased incidence of addiction and comorbid substance use, suicidality, and new-onset psychosis. Negative impacts on cognition and academic performance have also been observed.”

Taking a Closer Look at the Adverse Side Effects of Marijuana Use

Marijuana use comes with a long list of harmful side effects shared among all age groups that use marijuana. The key distinction is that young people seem to experience these side effects with more severity than the older adult and adult populations. Marijuana appears to harm the development and long-term mental, cognitive, and psychological state of young people (this effect is more pronounced the younger the individual is when he or she begins using).

Here are some of the adverse side effects of marijuana use, relevant to all age groups:

  • Altered sensory perception, uncertainty as to what is real.
  • An altered sense of time, not being present.
  • Mood changes, sometimes drastic and unpredictable.
  • Impaired body movement, loss of muscle coordination.
  • Difficulty with thinking, problem-solving, and cognitive function.
  • Impaired memory, sometimes permanent.
  • Hallucinations and delusions when taken in high doses.
  • Falling into a state of psychosis.

This is by no means a complete list. But marijuana use presents a clear and present risk for all ages, with young people perhaps the most at risk for particularly grievous harm.

Marijuana and Young People—Not a Healthy or Wise Combination

As legalization has made cannabis legally accessible for millions of young adults across the country, now more than ever, parents, educators, opinion leaders, public health experts, policymakers, and other young people must ensure that young adults understand the risks and dangers in marijuana use. Voters, policy makers, politicians, and health experts should protect young people by rallying against increasing marijuana legalization efforts.


Reviewed by Claire Pinelli, ICAADC, CCS, LADC, RAS, MCAP, LCDC-I



After working in addiction treatment for several years, Ren now travels the country, studying drug trends and writing about addiction in our society. Ren is focused on using his skill as an author and counselor to promote recovery and effective solutions to the drug crisis. Connect with Ren on LinkedIn.