Cannabis and Mental Health: What the Latest Research Says About Risks and Benefits

June 6, 2026

Cannabis and Mental Health: What You Need to Know

Muthukumar Vellaichamy, MD
CEO and Founder, KSP Health

Based on: JAMA Internal Medicine May 2026

🌿 Why This Matters

Over the past two decades, cannabis (also known as marijuana) has become more widely available in the United States. More people are using it—some daily or nearly every day. At the same time, cannabis products have become much stronger than they used to be.

Many people use cannabis for medical reasons. Studies suggest that:

✅ 10% to 30% of the general population who use cannabis do so to manage health-related symptoms

✅ Three out of four primary care patients who use cannabis report using it for symptom relief

As cannabis becomes more common, patients increasingly ask their doctors about its effects on mental health. However, many doctors feel they do not have enough knowledge or confidence to answer these questions.

This document summarizes what science currently tells us about cannabis and mental health. It is based on a 2026 review published in a leading medical journal and is intended to help you have informed conversations with your healthcare provider.

📖 Key Terms You Should Know

Term	What It Means
THC	The main psychoactive ingredient in cannabis. It is what makes you feel “high.” Higher THC means stronger effects and higher risks.
CBD	A cannabis ingredient that does not cause a “high.” It has attracted interest for possible medical uses, but research is still limited.
Cannabinoids	Chemical compounds found in cannabis. THC and CBD are the two most studied.
Potency	How strong a cannabis product is, based on its THC content.
Cannabis Use Disorder (CUD)	A problematic pattern of cannabis use that leads to significant impairment or distress, including craving, loss of control, and continued use despite harm.
Cannabis-induced psychosis	A temporary state of losing touch with reality (hallucinations, delusions) triggered by cannabis, usually high-THC products.

🧠 How Cannabis Works in the Brain

Your body has its own natural “endocannabinoid system” – a network of receptors that helps maintain balance in mood, memory, appetite, and stress response. This system normally works locally and briefly.

When you use cannabis, THC floods this system indiscriminately and stays active for a long time. It activates receptors throughout the brain – including areas that control mood, motivation, and memory. This is what causes the intoxicating (“high”) effects.

👉 Key point: The mental health effects of cannabis — both positive and negative — are closely linked to how much THC you consume and how often.

🔬 What the Science Says About Cannabis for Mental Health Conditions

😟 Posttraumatic Stress Disorder (PTSD)

Many people with PTSD use cannabis to cope with hyperarousal and sleep problems. However, the scientific evidence does not currently support cannabis as an effective treatment for PTSD.

What studies show:

• Only two small clinical trials have been published. The largest (80 veterans with PTSD) found no difference in PTSD symptoms between cannabis and placebo over three weeks.

Side effects:

• Dry mouth
• Nausea
• Dizziness
• Drowsiness

These were more common with THC-containing products than with CBD alone or placebo.

👉 Bottom line: Low-certainty evidence suggests cannabis does not reduce PTSD symptoms.

😰 Anxiety

About half of people who use cannabis for symptom management do so to treat anxiety. However, the effects depend heavily on dose and type of cannabinoid.

THC effects:

• Low doses (e.g., 7.5 mg oral THC) reduced anxiety in some healthy volunteers.

• Higher doses (12.5 mg) actually caused anxiety.

CBD effects:

• Several studies show that 300–600 mg of CBD can reduce acute anxiety, including fear of public speaking.

• CBD may also reduce the anxiety caused by THC.

Long-term use:

• There is insufficient evidence about the long-term effects of THC-predominant cannabis on anxiety disorders.

• Early evidence suggests high-dose CBD may be beneficial, but more research is needed.

👉 Bottom line: While CBD shows promise for acute anxiety, current evidence does not support cannabis as a long-term anxiety treatment.

😔 Depression

Many people believe cannabis helps with depression, but scientific studies do not support this.

What studies show:

• A meta-analysis found cannabis was not associated with improved depression symptoms.

• One prospective study found cannabis use did not lead to higher remission rates in major depression.

⚠️ Serious concerns:

Heavy cannabis use is associated with self-harm and suicidal behavior – especially in younger people.

• One study found that adolescents and young adults with mood disorders who had cannabis use disorder had a higher risk of self-harm and unintentional opioid overdose death.

• Veterans with cannabis use disorder had substantially higher rates of self-injurious behavior.

👉 Bottom line: Cannabis is not an effective treatment for depression, and heavy use may be harmful – particularly in younger populations.

🔄 Bipolar Disorder

The evidence here is clearer and more concerning.

What studies show:

Across seven observational studies, cannabis use in bipolar disorder was consistently associated with:

❌ Higher rates of mania

❌ Lower rates of recovery and remission

❌ More psychosis

❌ More social and employment problems

CBD research:

• One small 2024 trial found CBD did not improve depression and anxiety in bipolar patients with acute depression, though higher doses showed a nonsignificant benefit.

• A larger trial is ongoing.

👉 Bottom line: Patients with bipolar disorder should avoid regular cannabis use, especially high-THC products, given the consistent evidence of harm.

🧩 Psychosis and Schizophrenia

This is one of the most well-established risks of cannabis use.

Acute effects:

• THC can temporarily induce psychosis (hallucinations, delusions) that lasts several hours.

• CBD does not.

Long-term risk:

• About 50% of people who experience cannabis-induced psychosis may later develop a chronic psychotic disorder like schizophrenia with repeated use.

Adolescents at highest risk:

• A 2024 study found an 11-fold increased risk of psychotic disorders associated with cannabis use during adolescence.

Dose-response effect:

Compared to no use:

• Daily use: 1.76 times higher risk

• Weekly use: 1.35 times higher risk

Genetic vulnerability:

• Those with first-degree relatives (parent, sibling) with psychotic disorders are at even greater risk.

👉 Bottom line: Early, heavy cannabis use – especially during teenage years – significantly increases the risk of developing schizophrenia and other psychotic disorders.

🎯 Attention-Deficit/Hyperactivity Disorder (ADHD)

Cannabis use is common among people with ADHD – one-third to more than half of daily cannabis users meet criteria for ADHD.

The paradox:

Cannabis intoxication can cause symptoms that look like ADHD – attention deficits, poor working memory, and impaired decision-making. These deficits may persist in youth who use heavily.

Evidence gap:

• Only one small randomized trial has examined cannabis for ADHD.

• It found no statistically significant effects (positive or negative) on attention, memory, or cognition.

👉 Bottom line: There is no evidence supporting cannabis as a treatment for ADHD.

🚨 Cannabis Use Disorder (CUD)

CUD is a recognized medical condition characterized by loss of control over cannabis use, craving, continued use despite harm, tolerance, and withdrawal.

How common?

• About 30% of people who have used cannabis in the past year meet criteria for CUD.

Who is at higher risk?

• Younger people

• Males

• Those with a history of other substance use disorders

• Those who use cannabis more frequently and at higher doses

Treatments:

• Evidence-based non-drug treatments include cognitive behavioral therapy and motivational enhancement therapy, but these are not always accessible.

• There are currently no FDA-approved medications for CUD.

🧠 Cannabis and Thinking (Cognition)

Acute effects:

• THC-predominant cannabis causes dose-dependent deficits in verbal learning, working memory, executive function, and processing speed. These impair driving and raise safety concerns.

Chronic effects in adolescents:

• Regular cannabis use during the teenage years may lead to small but measurable declines in IQ.

Chronic effects in adults:

• Cognitive deficits may improve with abstinence, but it is unclear how quickly or completely.

💊 Drug Interactions

Cannabis can interact with many psychiatric medications. Always tell your doctor if you use cannabis so they can check for interactions.

Examples include:

• CBD can increase concentrations of the antiseizure medication clobazam, causing more drowsiness and unsteadiness.

• Cannabis can increase the sedating effects of benzodiazepines (like Xanax or Valium).

• Cannabis may affect how the body processes certain antidepressants and mood stabilizers.

✅ Practical Advice for Safer Decisions

If you choose to use cannabis – or are considering it – here is evidence-based guidance to reduce harm:

1️⃣ Prefer lower THC products.

Higher THC means higher risk of anxiety, psychosis, and other mental health harms. Avoid high-potency concentrates and dabs entirely.

2️⃣ Avoid use during adolescence and young adulthood.

The developing brain is uniquely vulnerable. Cannabis use during these years significantly increases the risk of psychotic disorders.

3️⃣ Do not use if you have bipolar disorder or a psychotic disorder.

The evidence of harm is consistent and strong.

4️⃣ Be cautious with depression and anxiety.

Cannabis may worsen symptoms, especially with heavy use. Heavy use in younger people with mood disorders is associated with self-harm.

5️⃣ Avoid during pregnancy.

Cannabis increases the risk of preterm birth and low birth weight.

6️⃣ Be aware of withdrawal.

Regular users who stop may experience insomnia, anxiety, restlessness, and agitation. These symptoms can be mistaken for worsening mental health, leading to continued use.

7️⃣ Avoid smoking as a long-term route.

Smoking cannabis increases bronchitis and may increase lung cancer risk.

8️⃣ Talk to your doctor. 😊

Be honest about your cannabis use. Doctors can check for drug interactions, screen for cannabis use disorder, and provide evidence-based guidance.