Schizophrenia and addiction is a common dual diagnosis. Studies have found that about half of people with schizophrenia also have substance use issues. That figure is much higher than the general population, which leads some people to wonder if substance abuse can cause schizophrenia.
Generally speaking, drugs do not cause schizophrenia, but they may trigger symptoms in people genetically disposed to schizophrenia. This has been of particular concern because of recent studies linking marijuana use to schizophrenia. It appears that teens who are predisposed to schizophrenia also, on average, use more marijuana and use it at a younger age. We aren’t yet sure why this is. It could be they are already having some symptoms that marijuana helps to mitigate, or that they respond more positively to marijuana. At any rate, marijuana appears to be a catalyst for a condition they already have. If you have a family history of schizophrenia, it’s best to stay away from marijuana.
The same is true of other psychoactive drugs. Psychedelics, especially LSD, have long been suspected of causing schizophrenia because they cause similar auditory and visual hallucinations. There are plenty of urban legends about people who used LSD, had a psychotic break, and had to be permanently committed. This situation is unlikely unless the person already had a genetic predisposition to schizophrenia. People who do have a genetic predisposition to schizophrenia should definitely not use LSD or other psychedelics. They may trigger symptoms or make the symptoms worse.
Stimulants are another drug of concern. An overdose of stimulants, especially cocaine, meth, or Ritalin can cause stimulant psychosis, which is very similar to schizophrenia. The two conditions are thought to be linked by a malfunction of dopamine signaling in the brain. Studies have shown that people who experience stimulant psychosis are five times more likely to have a relative with schizophrenia. It may be that people prone to stimulant psychosis have at least some of the genetic markers for schizophrenia. Typically, stimulant psychosis resolves on its own with about a month. In an estimated five to 15 percent of cases, psychotic symptoms persist indefinitely.
While drugs don’t appear to cause schizophrenia, they may precipitate symptoms or make them worse. Even alcohol can exacerbate the symptoms of schizophrenia. Also, about 80 percent of people with schizophrenia smoke. A recent study suggests this is because nicotine moderates the effect of antipsychotic medications. If you have a family history of schizophrenia or have already developed schizophrenia, it’s best to avoid drugs and alcohol completely.