The link between marijuana and psychosis goes beyond a short-lived high. If you already have schizophrenia and use the drug, your symptoms may get worse. You may have more psychotic episodes and spend more time in the hospital.
Researchers also have found that if you carry certain types of specific genes that affect brain chemistry, marijuana use can raise the chance you’ll have schizophrenia. One of those genes is called AKT1. Another is called COMT.
Cannabis may cause schizophrenia symptoms to start earlier in life, too. Typically, men show signs of the disorder in their late teens to early 20s, and women in their late 20s to early 30s. Using marijuana may make symptoms show up as much as 3 years earlier.
The age at which you start using marijuana also might make a difference. Earlier use, especially during the teen years, may mean a greater chance of having schizophrenia, perhaps because your brain is still developing during this time.
If you have a parent or sibling with schizophrenia, you already have a higher chance of getting the disease. Using cannabis can make your odds even worse, taking them from one in 10 to one in five.