How Does Medical Marijuana Legalization Affect Mental Health?

Marijuana Legalization and Mental Health
Medical marijuana legalization has been linked to various effects on mental health, with studies showing both potential benefits and concerns. Research indicates that while the number of cannabis users may increase with legalization, this does not necessarily result in a higher rate of mental distress. In terms of depression and anxiety, some studies suggest that low-dose THC can serve as an effective antidepressant and that CBD-rich products may alleviate symptoms of these conditions. However, the impact of marijuana on mental health can vary based on factors such as dosage and individual response. Additionally, there's evidence suggesting that legalization may not increase suicide rates and could potentially contribute to a reduction in these numbers.
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“You smoke a joint and you’re likely to kill your brother.”

This warning comes from Harry Anslinger, the infamous founding commissioner of the Federal Bureau of Narcotics. It’s been nearly 80 years since Anslinger fueled his war on drugs with a barrage of inflammatory, racist, and false statements that vilified cannabis as “loco weed.” And he wasn’t alone. A 1925 headline in the New York Times read: “Mexican, Crazed by Marihuana, Runs Amuck With Butcher Knife.”

Times have obviously changed, but this legacy of disinformation continues to cast shadows over the question of how medical marijuana laws (MMLs) affect mental health.

Medical Marijuana Laws: Real Problem or Just Perception?

In 2019, a paper from Missouri Medicine warned:

As more states rush to legalize the use of cannabis products, both medically and recreationally, there are more medical harms being seen in emergency departments.

On the surface, this might seem to be an indictment of legalization. But there’s more to the story. First, as the paper acknowledges, this trend is most likely related to the high-potency THC formulas favored by some recreational users. But there’s another factor in the equation which has to do with simple math. It goes like this: If one person in 100 has a problem, 10 in 1,000 will probably have the same problem. So more users equal the same percentage of problems – but numerically, more overall problems.

This phenomenon was confirmed by a 2020 online report from Drug and Alcohol Dependence which concluded that while implementing MMLs did increase the number of individuals using cannabis, it did not result in an increased rate of mental distress. The scholarly explanation was that:

Associations between elevated distress and cannabis use patterns are no greater in states with MML. However, cannabis use is more prevalent in MML states. Thus, higher base rates of cannabis use and disorder among adults with elevated distress are proportionally magnified in these states.

Marijuana Legalization: Depression & Anxiety

The numbers show that people suffering from depression are more likely to use marijuana. But numbers alone don’t answer this question: Does marijuana cause or worsen depression – or are depressed people more likely to use marijuana to help treat their symptoms?

A working paper from the National Bureau of Economic Research (NBER) reports that synthetic cannabinoids can have potent antidepressant effects in animal models. Clinical studies also indicate that low-dose THC can boost serotonin production and serve as an effective antidepressant. However, the same research warns that high doses of THC might have the opposite effect. (Keep in mind, all of these studies have involved animal modeling in laboratory settings, and may not translate to real-world use.)

At the human level, there is some recent evidence that medical marijuana legalization may provide benefits for anxiety conditions. A 2015 review of literature mentions a study involving 24 patients diagnosed with social anxiety disorder. Study participants who received a 600mg dose of cannabidiol performed significantly better on a simulated public speaking test. The report also indicated that “cannabidiol was associated with a significantly greater improvement in anxiety levels.”

One of the first comprehensive studies on the real-world use of marijuana for depression and anxiety was published in 2018 in the Journal of Affective Disorders. The authors called this research the first of it kind because it used self-reported data from people smoking marijuana in their own homes rather than subjects taking THC pills in a laboratory.

The authors used information from the app Strainprint, which lets medical marijuana patients track and report changes in symptoms based on their cannabis use. The data included 11,953 tracked sessions: 3,151 for depression, 5,085 for anxiety, and 3,717 for stress. After crunching the numbers, they reported:

  • Medical cannabis users perceived a 50% reduction in depression and a 58% reduction in anxiety and stress following cannabis use.
  • Two puffs were sufficient to reduce ratings of depression and anxiety, while 10+ puffs produced the greatest perceived reductions in stress.
  • High CBD (>9.5%)/low THC (<5.5%) cannabis was associated with the largest changes in depression ratings.
  • High CBD (>11%)/high THC (>26.5%) cannabis produced the largest perceived changes in stress.

Another study from 2020 also used app-based reporting of real-world cannabis use for treating depression. Of the 1,8000 people who participated in the study, some 96% reported a decrease in symptoms of depression after smoking marijuana.

More insights come from Frontiers in Psychiatry. For a study released in 2021, researchers surveyed 538 people who reported having depression, anxiety, or both. Participants include 368 current medical cannabis users and 170 people who were not using cannabis medicinally but were considering doing so. The study concluded:

  • Medical cannabis use was associated with lower self-reported depression.
  • Medical cannabis users also reported superior sleep, quality of life, and less pain on average.
  • Participants who used cannabis, particularly CBD-rich products, reported lower levels of depression than non-users.
  • Non-users who started cannabis during a follow-up period to the initial survey reported significantly decreased anxiety and depressive symptoms.

The study’s lead author is quoted as saying:

Medicinal cannabis products, especially products high in CBD, may help to treat symptoms of depression, improve sleep, and increase quality of life. There is also some evidence that medicinal cannabis may alleviate symptoms of anxiety, particularly if administered over an extended period of time.

Marijuana Legalization & Suicide

According to the NBER report mentioned earlier, there’s some good news regarding the relationship between medical marijuana legalization and suicide rates. The short version is that:

  • Legalization does not appear to increase suicide rates, and
  • There are some indications that legal access to therapeutic cannabis may play a role in reducing suicide numbers.

These conclusions are based on three individual studies that the NEBR authors felt had the highest degree of credibility.

A report released in 2014 compared state-by-state suicide rates from 1990-2007 to the adoption of medical marijuana laws. The data, which was obtained from the CDC’s National Vital Statistics System, showed that the adoption of MMLs was associated with an overall 5 to 6% reduction in male suicide rates. These reductions were even greater for younger and early middle-aged men. Specifically, the authors found that MML adoption is associated with an:

  • 11% reduction in suicides among men ages 20 to 29
  • 9% reduction in suicides among men ages 30 to 39

One potential explanation given for this phenomenon was that men in these groups may be using marijuana to cope with stressful life events.

The following year, another research team started with the same CDC information, then applied some additional filters to account for things like state-by-state spending on mental health care and specific social and economic factors that might skew the data. Their adjusted data showed a similar 4 to 6% reduction in suicide rates following marijuana legalization.

In 2020, the Archives of Suicide Research reported that suicides in California fell by around 400 deaths a year after medical marijuana legalization. They noted that this reduction was related to a drop in gun-related suicides. The vast majority of suicides in the U.S. involve firearms and California state law disqualifies individuals holding a medical marijuana card from legally purchasing a firearm.

Marijuana Legalization & General Well-Being

If medical marijuana legalization really does have a positive effect on overall mental health, the numbers should support this phenomenon. One source that does so is a 2018 discussion paper from the Centre for Economic Performance. This report used records from the CDC’s Behavioral Risk Factor Surveillance System that included more than 6 million cases over a 22-year period. The report concluded:

Overall, we find no evidence that MMLs have a detrimental effect on mental health. On the contrary, we observe overall reductions in the number of bad mental health days.

Digging a little deeper, the authors determined:

[Improvements in mental health days] are concentrated mainly in the first three years following the introduction of the laws.

And that:

Improvements primarily arise in states that have the most liberal medical marijuana regimes (specifically, those that allow the prescription of cannabis for unspecific pain).

To date, most all studies on marijuana legalization and mental health have focused on medical marijuana laws. A new study released in late 2022 is billed as the first to consider the implementation of recreational marijuana laws (RMLs) on standard measures of mental health. Study conclusions were based on two metrics of mental health – the first being the self-reported number of days of bad mental health, the second coming from a standard test used to determine overall mental well-being.

At first glance, the results might seem a bit underwhelming, as the authors reported that RMLs adoption didn’t appear to create any overall change in public mental health. In other words: a “null effect.” But a different picture emerged when age was factored into the equation. It seems that this null effect was created by offsetting trends. The authors report:

Elderly individuals (age 60 and older) benefit from medical marijuana legalization in terms of better mental health, whereas legalizing recreational marijuana produces negative mental health effects for younger individuals (below age 35).

They noted that MMLS laws improved mental health for older users largely due to reductions in pain and enhanced symptom management. By contrast, MMLs did not appear to affect mental health scores among younger users. According to the study, this changed when RMLS came into effect. In states where recreational marijuana became available, the under-35 users showed an average increase in their reported number of poor mental health days. The authors attributed this trend to “overuse rather than use of marijuana as a medical treatment.”

These results do not suggest that the responsible consumption of marijuana puts all younger adult-age users at risk of mental health issues. Instead, they likely represent problems associated with substance abuse by a subset of younger users.

CannaMD is one of Florida’s leading advocates for the informed and responsible use of medical marijuana. We will continue to keep readers apprised as additional research emerges regarding marijuana legalization and mental health.

Updated: May 28, 2024

Article Written By:

Pierce Hoover

Pierce Hoover is a career journalist with more than three decades of experience in print, broadcast and online writing, editing and reporting, with more than 5,000 articles published in national and international print media and online. His focus on medical marijuana therapies mirrors his broader interest in science-based alternative medical practices.


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