Marijuana has side effects, too. Fortunately, the side effects are usually mild to moderate and resolve quickly, but they can be severe when the patient does not adhere to the physician's dosage instructions.   That said, people with schizophrenia should avoid marijuana products containing high levels of THC because it can worsen psychosis. The side effects of medical marijuana include; Increased heart rate Dry mouth Impaired memory Hallucinations (when consumed in high doses) Delusions (when consumed in high quantities) Psychosis (when you consume high-potency marijuana)