How can illegal drug use affect schizophrenia?

While there may not be a causal relationship, per se, between schizophrenia and substance abuse, there is strong evidence that using certain drugs can trigger an onset or relapse in some people. Individuals with schizophrenia may also use substances such as alcohol and drugs to "self medicate" by trying to eliminate unpleasant symptoms or side effects of medication. In fact, one study shows that 60% of people with schizophrenia used substances of one kind or another, with 37% having a diagnosable substance abuse disorder. Amphetamines and hallucinogenic drugs may worsen schizophrenia symptoms.

There is evidence that cannabis (known in its herbal form as marijuana or ganja, or as hash in its resinous form) use can contribute to schizophrenia and, in fact, may be a significant causal factor. Some studies indicate that cannabis actually doubles the risk of developing schizophrenia as compared to those who have not used cannabis.
Taking illegal drugs and drinking too much alcohol are problems for some people with schizophrenia. When a person is using drugs, they are less likely to follow a treatment plan.
Most experts believe drugs and alcohol do not cause schizophrenia, but they may make antipsychotic medications less helpful. Also, drugs like marijuana make symptoms worse.
It is very common for people with schizophrenia to smoke cigarettes. However, smoking may make the medications less useful. It is hard for people to quit smoking because it might make their schizophrenia symptoms worse for a while. Doctors need to help any patient with schizophrenia who wants to quit smoking.
This answer from the National Institute of Mental Health has been reviewed and/or edited by Dr. William D. Knopf.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.