Cannabis aficionados often emphasize the positive aspects of marijuana and related products, citing a range of generally not well-evidence-informed applications in pain management, mental health, creativity, and recreational or social use. While some studies suggest cannabis may be effective for certain types of pain, insomnia, and a small handful of conditions, the enthusiasm—and often the marketing in this lucrative space—does not always align with the data. Cannabis is not universally benign and may cause serious harm for some individuals. For instance, in a 2021 review and meta-analysis, Kiburi and colleagues found a 1.7-fold increased risk and earlier-onset of psychotic illness among adolescent cannabis users.

Despite cannabis’ widespread appeal and the growing number of U.S. states approving medical marijuana, research does not support broad efficacy for a range of conditions. Studying people with medical marijuana cards increases the likelihood that they are using quality-controlled cannabis products rather than street products, which may be adulterated with harmful and unpredictable synthetic chemicals. A 2022 study at Massachusetts General Hospital (Gilman et al., 2022) followed 186 individuals who had obtained medical marijuana cards for various complaints.

They found that having a medical marijuana card significantly increased the risk of developing problematic cannabis use (Cannabis Use Disorder, CUD). Additionally, medical marijuana was not associated with improvement in pain, depression, or anxiety. While patients self-reported improvement in insomnia, sleep quality was not objectively measured in this study.

Large Population Studies

Two population-based studies published in JAMA Open, the Journal of the American Medical Association, reinforce these concerns.

A large study analyzing data from 11.6 million individuals treated in emergency rooms and during hospitalizations in Ontario, Canada (Myran et al., 2025), found an overall 2.8-fold increased risk of death among those with CUD compared to the general population. The study, which analyzed data from 2006 to 2021, adjusted for other health risks, including other substance use, chronic physical conditions, and mental health disorders. Patients in the CUD group met the criteria for cannabis use disorder rather than being light or recreational users.

Among individuals in the CUD group, 3.5% died compared to 0.6% in the matched comparison group, which accounted for non-CUD-related health risks to ensure an accurate assessment of CUD-specific mortality.

Mortality for all causes of death was elevated, with the following specific risks reported as “adjusted hazard ratios” (a metric indicating how many times higher the risk is for a given cause of death):

• Suicide: 9.7
• Trauma: 4.55
• Opioid poisoning: 5.03
• Other drug poisoning: 4.56
• Lung cancer: 3.81

Mortality risk was also elevated for individuals with alcohol and other substance use disorders. While CUD presented a lower risk compared to other substance use disorders, the risk remained notably high—independent of other factors.

A second study (Myran et al., 2025) examined whether rates of newly diagnosed schizophrenia changed after marijuana legalization. This is critical, as prior research has shown that cannabis use—particularly among adolescents and young adults—can interfere with brain development and increase the risk of psychotic disorders. Using data from 13.5 million people without schizophrenia, collected between 2006 and 2022, researchers found that 8.9% of individuals in the CUD cohort developed schizophrenia, compared to just 0.7% in the comparison group. This represents a nearly 13-fold increased risk of schizophrenia among heavy cannabis users.

Proceed With Caution

At the same time, it is not uncommon for marijuana enthusiasts to claim multiple benefits and for cannabis companies to make health claims—often accompanied by the disclaimer that these statements have not been evaluated by the FDA. This issue is widespread in the multi-billion-dollar wellness industry, where pseudoscientific methods, supplements, and drugs are heavily marketed. While there are valid critiques of mainstream biomedical research, particularly regarding conventional psychiatric medications, these critiques should not be used to obscure strong data indicating that cannabis is far from benign—and may not be therapeutic for many who use it. While occasional recreational use is likely safe for people without risk factors, monitoring for excessive use and weighing risks and benefits—as with any substance—is essential. The appropriate medical use of marijuana is increasingly understood to be much more circumscribed than many would like. Far from being a miracle cure, cannabis can sometimes do more harm than good.

Unfortunately, even in cases where medical marijuana cards are required, evaluations and discussions of risks and benefits are often inadequate, making it difficult to determine who may actually benefit from cannabis and who may be at risk for CUD, increased disability, or death.

Taken together, these studies—and others not discussed here—raise significant public health concern. The widespread legalization of cannabis and increased access to medical marijuana are associated with a higher risk of cannabis use disorder, substantially elevated mortality rates across various causes of death, with minimal demonstrated benefit for mental health or chronic pain.