New Analyses Suggest Cannabis Offers No Proven Relief for Anxiety, Depression

Bad news for some cannabis users: both recreational and medical cannabis use seem to be ineffective in reducing the symptoms of various mental health conditions, according to 2 recent studies. The Lancet Psychiatry published a major meta-analysis conducted by the University of Sydney’s Matilda Centre for Research in Mental Health and Substance Use. Researchers went down from an initial pool of 5,774 studies to 54 randomized controlled trials involving 2,477 participants and conducted between 1980 and May 2025. The results indicated that cannabis did not provide significant relief for anxiety, depression, or post-traumatic stress disorder. These findings are especially important because these 3 conditions are the primary reasons patients seek medical marijuana prescriptions. 

 A second study reaches the same conclusion

A concurrent review published in JAMA Internal Medicine added to the evidence of these results. This review, led by Dr. Deepak Cyril D’Souza of the Yale Center for the Science of Cannabis and Cannabinoids, examined both natural and synthetic THC and CBD. The JAMA study found that evidence claiming benefits for conditions like ADHD, depression, and anxiety was grossly misrepresented and inaccurate. The study also noted low-confidence data on THC-dominant cannabis and its failure to reduce PTSD symptoms. The Lancet and JAMA analyses gain reliability by using randomized controlled trials that account for placebo effects and expectation bias, which can distort results in less careful observational studies.

The gold standard of evidence

Researchers consider randomized controlled trials (RCTs) the most rigorous source of clinical data. They account for expectancy bias, self-selection, and placebo effects in these studies, as these factors often lead to exaggerated findings in observational or real-world research. The JAMA review and the Lancet meta-analysis present findings of no significant benefit that are particularly difficult to dispute because both rely solely on RCT data. For instance, a 2021 PubMed review of eight studies concluded that insufficient evidence exists to support the use of CBD and THC for anxiety, PTSD, or affective disorders, ultimately advising against recommending medical cannabis.

Lack of Research on Cannabinoids for Depression and Its Implications

The Lancet review highlighted a significant lack of research into the primary reasons for cannabis use, noting that researchers have never conducted randomized controlled trials (RCTs) to investigate the efficacy of cannabinoids for depression. This lack of rigorous testing creates a significant clinical gap, given that in states where medical cannabis is legal, depression is the most common reason for patients to seek prescriptions for cannabis. Despite this absence of gold-standard evidence, physicians continue to approve its use, a practice that researchers like Wilson suggest should be reconsidered until formal scientific validation is achieved.

Additionally, the cannabis industry has financial ties to many ongoing studies, which creates a major conflict of interest. The validity of more thorough research is called into question because these commercial relationships may lead to the systematic exaggeration of therapeutic benefits. Such changes could weaken the evidence that healthcare providers and regulatory bodies use. To present a more objective perspective, the Lancet and JAMA analyses deliberately avoided potential biases by concentrating only on data from randomized controlled trials, which are better able to account for placebo effects and expectancy bias.

A Prescription-Evidence Gap That Cannot Be Ignored

Medical cannabis prescriptions are increasing despite a lack of clinical trial support. According to data, approximately 27% of people aged 16 to 65 in the United States and Canada have used cannabis for medicinal purposes, with roughly half of those users specifically targeting mental health symptoms. Furthermore, cannabinoid medication sales in Australia tripled over a 4-year period, exceeding 1 million prescription approvals. This significant expansion occurred even though no randomized controlled trial (RCT) evidence exists to justify its use for the specific conditions being treated. 

Depression has zero trials

The Lancet review revealed a significant lack of research into the primary reasons for cannabis use. Specifically, no randomized controlled trials have ever looked into the efficacy of cannabinoids in the treatment of depression. This creates a significant clinical disconnect, as depression is the leading reason for medical cannabis prescriptions in legalized states. Despite the lack of gold-standard clinical testing, physicians continue to approve its use for this condition, which Wilson believes should be reconsidered given the lack of formal scientific validation. 

Industry influence on the science

Wilson emphasized a significant “conflict of interest,” noting that the industry holds financial stakes in several ongoing studies, which undermines the reliability of cannabis research. These business ties may lead to an exaggeration of therapeutic benefits, jeopardizing the entire research process from planning to final reporting. This compromises the evidence base for regulatory agencies and physicians who rely on that literature. Although the broader research landscape remains uneven, the two new analyses actively avoided this distortion by focusing solely on RCT data.

What Studies Tested Versus What People Actually Use

The RCT evidence base has one significant limitation. The trials included in the Lancet review examined standardized pharmaceutical cannabinoids. Researchers used isolated CBD in 24 experiments and isolated THC in 18. They used only 12 fixed-ratio combinations. In real-world settings, medical cannabis users typically prefer whole-plant products that feature various terpene and cannabinoid profiles. These trials’ controlled environments don’t accurately represent what patients eat daily outside a clinical setting. Experts argue that the limited pharmacological window may cause the RCTs to inaccurately reflect the effects of the products that are actually prescribed.

Smoked cannabis remains understudied

Wilson identified a significant disparity in common consumption patterns. Although clinical trials focused on oral preparations such as oils, sprays, and capsules, the majority of actual users prefer to smoke or vaporize cannabis. As a result, compared to oral alternatives, the randomized controlled trial (RCT) data on the effects of smoked cannabis on mental health are even more limited. Wilson emphasized that the already limited evidence of efficacy for this primary delivery method is exacerbated by the fact that real-world use typically entails smoking.

Limited signals in specific conditions

The Lancet review found a few minor, low-quality positive outcomes for a few diseases. Researchers have shown that a combination of THC and CBD reduces both the frequency of weekly use and the severity of withdrawal symptoms in people suffering from cannabis use disorder. Studies link cannabinoids to a reduction in autistic traits in individuals with autism spectrum disorder and a decrease in the intensity of tics in those with Tourette’s syndrome. While insomnia showed a slight improvement, researchers classified these findings as low-quality evidence that is not yet strong enough to guide clinical protocols. Although these observations suggest that cannabis research does not always produce negative results, they do not contradict the study’s main conclusion.

The Real Risks of Cannabis for Mental Health

The evidence for benefit is lacking, but the evidence for harm is substantial. According to D’Souza, daily users of high-potency cannabis are 6 times more likely than non-users to develop a psychotic disorder such as schizophrenia or bipolar disorder. The JAMA review confirmed that THC-predominant cannabis use carries a significant risk of negative mental health effects, including worsening mania in bipolar disorder patients. According to Mass General Hospital’s psychiatry division, youth who use high-potency THC cannabis are 3 times more likely to develop psychotic disorders than those who have never used cannabis. 

Adolescents carry the highest risk

Teenagers face a significantly higher risk profile. A 2024 study published in Psychological Medicine and led by CAMH researchers found that teens who used cannabis had an 11-fold higher risk of developing a psychotic disorder than teens who did not use cannabis. This is a significantly stronger relationship than previous estimates. Potency plays a role in this explanation. Much of the older data used in previous analyses predates the era of high-THC cannabis, implying that prior risk estimates likely underestimate the actual dangers that current adolescents face.

Cannabis worsens outcomes in existing mental illness

The use of cannabis after a mental health diagnosis tends to exacerbate the severity of the condition. According to one analysis, cannabis appeared to exacerbate symptoms in every study reviewed for patients who already had PTSD and cannabis use disorder. People suffering from mood disorders who heavily use cannabis are more likely to self-harm or attempt suicide. Heavy cannabis use also doubles the likelihood of abandoning cognitive-behavioral or pharmacological PTSD treatments and decreases compliance with trauma-focused psychotherapy. Finally, patients who combine cannabis with clinical care face greater treatment challenges and a higher risk of relapse. 

Today’s Cannabis Is Not What It Was

The cannabis available today is vastly different from what existed decades ago. The average THC content in the 1960s and 1970s ranged between 1% and 2%. It had reached around 4% by the 1990s. Herbal cannabis currently has an average THC concentration of 18% to 23%. Products available at licensed dispensaries typically contain THC concentrations of 35% or higher. Cannabis concentrates tested at THC levels of 80% or higher, which is roughly 20 times the potency of cannabis 50 years ago. The American Psychological Association stated in 2025 that this potency trajectory is still accelerating with no signs of slowing.

The addiction risk is growing with potency

Higher potency cannabis is causing a noticeable increase in addiction. According to the US Centers for Disease Control and Prevention, roughly 3 out of every 10 marijuana users meet the criteria for cannabis use disorder. Dependence characterizes cannabis use disorder, leading to withdrawal symptoms like irritability, restlessness, mood disturbances, sleep difficulties, and altered appetite when individuals stop using it. That figure includes more than 16 million Americans aged 12 and up. Adolescents are especially vulnerable, with research showing that regular high-THC use during youth increases the risk of psychosis by two to eleven times, depending on the frequency and potency of use.

Treatment uptake is declining as use rises

Despite rising rates of cannabis use disorder, fewer people seek treatment. The percentage of people with cannabis use disorder who received any type of treatment fell from 19% in 2003 to 13% in 2019. Barriers include a lack of knowledge about where to seek help, a reluctance to quit, concerns about job consequences, and an inability to afford care. According to the Drug-Free America Foundation, the treatment gap will widen as legalization normalizes use and reduces perceived risk. The disparity between the size of the problem and the rate of treatment engagement is a growing public health concern.

What the Evidence Does Support

Anxiety and depression treatment options have been clinically validated. Selective serotonin reuptake inhibitors (SSRIs) are the most commonly prescribed medication for both conditions. Because of their established safety, efficacy, and tolerability profiles, SSRIs are classified as first-line pharmacotherapy for depression and various other psychiatric disorders in StatPearls, the National Institute of Health’s clinical reference database. SSRIs are particularly effective for depressive mood and psychic anxiety, making them an ideal intervention for the conditions that drive the majority of medical cannabis prescriptions. 

Cognitive behavioral therapy as the leading psychotherapy

Cognitive behavioral therapy (CBT) is the leading evidence-based psychotherapy for anxiety and depression. CBT actively targets negative thought patterns and behaviors to enhance emotional regulation. Research published in PMC confirms that combining SSRIs with CBT produces greater improvement than either treatment alone, particularly in the medium to long term. The Association for Behavioral and Cognitive Therapies keeps a searchable database of CBT-trained therapists. The American Psychological Association also includes CBT-trained providers in its “Find a Psychologist” tool under treatment methods. 

The cost of delaying proven care

Choosing cannabis over evidence-based treatment carries a clinical cost beyond the direct risks of the substance itself. Wilson noted that routine cannabis use for mental health could delay access to treatments with a proven track record. That delay is not neutral. Untreated anxiety and depression worsen over time, and the window for early intervention carries prognostic significance. Patients who use cannabis in place of SSRIs or CBT are not simply choosing a less effective option; often, they are postponing care that could have meaningfully changed the course of their condition.

The Regulatory Question

Another regulatory failure is the difference between prescriptions and evidence. D’Souza pointed out that almost every state in the United States allows medical marijuana for mental health conditions. Despite the lack of clinical trial evidence supporting its use for those conditions, the approval continues to grow. The two 2026 analyses make this contradiction explicit. Wilson stated that the findings directly call into question the routine approval of medical cannabis for depression, anxiety, and PTSD. As a direct result of their findings, both research teams advocated for stricter clinical oversight of medicinal cannabis prescriptions. 

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Calls for tighter oversight

Both the Lancet and JAMA research teams used their findings to push for regulatory reform. The current model, in which prescription approvals outpace the available evidence, creates a system where patients bear risk without proven benefit. The researchers stopped short of calling for an outright ban but emphasized that, without credible evidence of efficacy, the routine prescription of medical cannabis should not continue at the current scale. A 2024 review in BJPsych Open reinforced this position, noting that pharmaceutical THC increased adverse events and withdrawals from treatment across multiple studies. Further research into specific formulations, dosing regimens, and subpopulations remains necessary before any revision to that position is clinically warranted. 

A market that has run ahead of the science

The US cannabis market was valued at $38.50 billion in 2024 and is projected to nearly double within five years. That scale of commercial growth is difficult to reconcile with an evidence base that, at its most rigorous level, shows no benefit for the most common conditions driving sales. The industry holds financial stakes in research outcomes and marketing narratives that do not always align with what controlled clinical trials show. According to drug abuse statistics published in 2026, 51% of American adults have tried marijuana at least once, and 25.7% of 12th-graders used it in 2025 alone. Patients making decisions about their mental health deserve a clearer separation between what the market sells and what the science actually supports.

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