Marijuana use can accelerate the development of psychotic illnesses and leave life-long damage, a study conducted by the GW School of Medicine and Health Sciences found.

Researchers discovered that marijuana use can hasten the onset of schizophrenia and other psychotic disorders by up to 2.7 years, a fact researchers discovered while determining the extent of the link between marijuana usage and psychosis.

Patient data from 83 previous studies was re-examined to find the link, Dr. Matthew Large, one of the researchers, said.

He also said individuals in mental health facilities and schizophrenics are more frequent substance-users.

“Results of this study are conclusive and clarify previously conflicting evidence of a relationship between cannabis use and the earlier onset of a psychotic illness, with evidence supporting the theory that cannabis use plays a causal role in the development of psychosis in some patients,” Large said.

Large said the study offers “strong evidence” that some psychosis cases would be delayed or prevented entirely if cannabis use was reduced or eliminated.

Genetics and environmental disorders could also be a factor in the connection, or disrupted brain development, according to the study.

The study was conducted jointly by the SMHS and the University of New South Wales, and tested more than 20,000 patients.