Mental Effects of marijuana Long-term marijuana use has been linked to mental illness in some people, such as: temporary hallucinations temporary paranoia worsening symptoms in patients with schizophrenia—a severe mental disorder with symptoms such as hallucinations, paranoia, and disorganized thinking Marijuana use has also been linked to other mental health problems, such as depression, anxiety, and suicidal thoughts among teens. However, study findings have been mixed. Contact your doctor for help. Dr Rohan jahagirdar MD