Schizophrenia, a rare but serious mental illness, impairs the way you think, make decisions, and handle emotions. There’s no single cause of the condition -- it’s a complicated disease that involves many factors. Genetics play a part. Viruses or poor nutrition before birth might as well. Issues with key brain chemicals can make you more likely to get the disease. Scientists also are continuing to study the role of drug use -- including marijuana -- in schizophrenia.

An Established Link One analysis of several studies found that marijuana, also called cannabis, is one of the most commonly abused substances among people with schizophrenia. Young people with the condition, in particular, may abuse it more often than alcohol. Researchers have puzzled over what that link means. Some say that people with schizophrenia may be more likely to use the drug because they’re looking for ways to ease their symptoms. But it’s unlikely that self-medication alone can explain the relationship between marijuana use and schizophrenia.

Pot and Psychosis One thing that marijuana and schizophrenia have in common is psychosis. It isn’t a mental illness -- rather, it’s a symptom. When you have psychosis, your thoughts are disrupted in a way that makes it hard for you to tell what’s real and what’s not. You might see or hear things that aren’t there, or you might have strange thoughts that won’t go away. Psychosis is a symptom of schizophrenia. Studies have found that when you’re high on marijuana, you can have psychotic symptoms. The effect goes away as the high wears off. Scientists think the main ingredient in marijuana that causes psychotic symptoms is THC (delta-9-tetrahydrocannabinol).