Cannabis may increase the risk of schizophrenia, particularly in people with a genetic predisposition for developing schizophrenia.

Schizophrenia is a mental illness that alters how people think, feel, and behave. Schizophrenia can cause psychosis, in which a person loses some contact with reality and may experience symptoms such as hallucinations and delusions.

Weed, which people may also refer to as cannabis or marijuana, may be a risk factor for developing psychosis.

This article looks at the link between cannabis use and schizophrenia symptoms. It also outlines the treatment options and explains when to contact a doctor.

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According to a 2021 article, cannabis use is a risk factor for developing a mental health condition or making an existing one worse.

Adolescents or young adults who consistently use cannabis may risk developing a psychotic disorder, such as schizophrenia. People with a genetic predisposition to schizophrenia may have an increased risk.

Up to 25–30% of people who visit the emergency department due to cannabis use will have symptoms such as:

The mind-altering component of cannabis is delta-9-tetrahydrocannabinol (THC). Cannabis also contains other compounds that are chemically related to THC. These are called cannabinoids.

In people with schizophrenia, cannabis use may worsen the course of the condition.

According to a report from the National Institute on Drug Abuse (NIDA), cannabis use, especially in high doses, can cause a short-lived psychotic reaction in people without schizophrenia. As the drug wears off, the symptoms fade.

Symptoms such as paranoia, anxiety, or psychosis may be present during the initial stage of intoxication. Impaired coordination and learning and sleep problems are among the effects that can last longer but may not be permanent.

Repeated use of cannabis can have cumulative effects that can cause long-term symptoms.

Doctors may diagnose cannabis intoxication when recent cannabis use has led to significant changes in a person’s behavior or mind. Cannabis intoxication can occur within minutes if a person inhales the drug, but it takes hours to appear following ingestion.

The duration of symptoms can depend on a person’s tolerance and the dose they take. Although they typically last for 3–4 hours, they can persist for up to 24 hours.

Many people who present to the emergency department with psychotic symptoms relating to cannabis use will need hospitalization. Up to 50% of these individuals will develop schizophrenia.

Psychosis usually develops over time, with a person experiencing gradual changes in their thoughts and perceptions. They may be unaware of these changes.

Pre-psychosis symptoms are early warning signs of psychosis. They include:

  • a worrying decline in school grades or work performance
  • difficulty concentrating or thinking clearly
  • feeling suspicious or uneasy around others
  • a decline in personal hygiene or self-care
  • spending much more time alone than usual
  • a lack of feelings or very strong, inappropriate emotions

The symptoms of psychosis may include:


Delusions are irrational, false beliefs or strong beliefs that are unusual for the person.

People may think that external forces are taking control of their thoughts and behaviors. They may believe that trivial objects have great significance, that they have superpowers, or that they are on a special mission.


Hallucinations occur when people see, hear, or feel things or sensations that are not real.

People may hear voices, experience strange sensations that they cannot explain, see things distortedly, or see objects or people that are not there.

Disorganized thoughts

People may have disorganized thoughts and speech patterns that seem jumbled and do not make much sense to others.

For instance, they may switch randomly from one topic to another or reply with an unrelated remark. Disorganized thought and speech can severely affect how people communicate.


Some people with schizophrenia may experience dissociation symptoms, such as a detached feeling or a disconnection from their body and the world around them.

People may feel as though things around them are not real, and they may be unable to remember information about themselves.

Emotion, mood, and behavioral changes

A person’s behavior and speech may change, and they might speak in a dull monotone or lack facial expressions.

Their movements might suddenly become agitated or childlike. Alternatively, a person may become catatonic and have a very limited response to their surroundings.

Other common changes include social withdrawal and difficulty making decisions or carrying out everyday tasks.

Learn more about the symptoms of schizophrenia.

For people in the early stages of psychosis, coordinated specialty care (CSC) may be an effective treatment. CSC involves a team of healthcare professionals working with the person and their family to provide:

  • family support and education
  • psychotherapy
  • peer support
  • support with education and employment

The treatment for psychosis or schizophrenia may include psychotherapy and medications, such as antipsychotic drugs.

People may also require therapies that help reduce cannabis use. These may include:

  • Cognitive behavioral therapy (CBT): CBT is a type of psychotherapy that gives people strategies to identify and change negative patterns of thought and behavior.
  • Contingency management: This approach involves frequent monitoring of the behavior that a person is working to change and provides incentives or rewards for positive changes.
  • Motivational enhancement therapy: This therapy aims to motivate the person to use their internal resources to engage in treatment and create positive changes.

Learn more about CBT for schizophrenia.

Anyone who experiences psychosis or pre-psychosis symptoms or notices them in someone else should contact a doctor. Early treatment can slow or stop psychosis and improve the likelihood of a good outcome.

It is also important to seek help for a cannabis misuse disorder. A doctor or mental health professional can discuss the treatment options with the person.

Early treatment of psychosis, during either pre-psychosis or the first episode of psychosis, may provide the best outlook.

Psychotherapy and medications can help manage and reduce the impact of psychosis and schizophrenia symptoms.

According to the Treatment Advocacy Center, a person should continue with treatment even after recovering from an acute episode of psychosis. The reason for this is that 80% of people who discontinue their medication will relapse within 1 year. For people who continue their medication, the relapse rate is 30%.

Cannabis use may cause psychosis and other symptoms that affect a person’s mood and cognitive function. The effects may disappear as the drug wears off.

In some people, consistent use of cannabis may cause symptoms of schizophrenia, particularly if they have a genetic predisposition to the condition.

Anyone who experiences any symptoms of psychosis should speak with a healthcare professional as soon as possible. Early treatment can help improve outcomes and recovery.