Cannabis and Mental Illness

Marijuana (Cannabis sativa) is the most commonly used illicit drug worldwide as well as in the Unites States. Prolonged use of marijuana or repeated administration of its primary psychoactive constituent, Δ9-tetrahydrocannabinol (THC), can lead to physical dependence in humans and laboratory animals. The changes that occur with repeated cannabis use include alterations in behavioral, physiological, and biochemical responses. A variety of withdrawal responses occur in cannabis-dependent individuals: anger, aggression, irritability, anxiety and nervousness, decreased appetite or weight loss, restlessness, and sleep difficulties with strange dreams. The medical community is now beginning to accept the idea that cannabis-related disorders represent a clinically significant public health problem.

mental disorder

Cannabis Causes Psychiatric Disorders

In addition to producing dependence, cannabis use is associated with a wide range of psychiatric disorders. There is a clear relationship between the use of cannabis and psychosis, different hypotheses for the same have been propounded. There is strong evidence that cannabis use may precipitate schizophrenia or exacerbate its symptoms. There is also reasonable evidence that cannabis use worsens the symptoms of psychosis.

Cannabis and Schizophrenia

There is a growing amount of evidence linking a variety of environmental factors and their impact on the emergence of psychotic disorders. The environmental factors include pre- and perinatal insults, stress and trauma, family environment, and cannabis use.

In observational studies, there has been consistent evidence that cannabis use is associated with an increased risk of schizophrenia and more generally, psychosis. In the intervening years there has been a steady increase in the number and quality of research studies that have been conducted exploring the links between cannabis use and psychosis.

Early Cannabis Use Causes Depression in Adults

Recreational cannabis use occurs across the globe. In recent decades, the age of initiation has declined, and concern about the public health impact has mounted. Statistically significant associations between cannabis use and anxiety and major depressive symptoms or disorders have been found in some high-income countries.


  1. Marijuana Dependence: Not Just Smoke and Mirrors
  2. Chemistry, Metabolism, and Toxicology of Cannabis: Clinical Implications
  3. Environmental Risk and Protective Factors and Their Influence on the Emergence of Psychosis
  4. Should Burden of Disease Estimates Include Cannabis Use as a Risk Factor for Psychosis?



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