Study: legalizing cannabis does not increase psychosis

A new study published this month in Jama Network Open shows no increase in psychosis-related disturbances or incidents among American states that have legalized cannabis for adult or medical use.

The researchers used the database Optum Clinformatics Data Mart, which contains insurance data for more than 63 million unique individuals tracked between January 1, 2003, and December 31, 2017. All beneficiaries aged 16 and older with at least one month of insurance eligibility during the period were included in the study.

The study authors used the number of unique claims with diagnoses related to psychosis, prescribed antipsychotics and the number of enrolled individuals for each month of follow-up, and merged the data with time-varying categorical measures of state cannabis policy and the state’s demographic, economic, and social characteristics.

Researchers identified more than 7 million diagnoses related to psychosis and recorded more than 20 million filled prescriptions for antipsychotic medications during the study period. And, during the study period, reforms regarding medical or adult-use cannabis were approved in 29 states.

«In this retrospective cohort study of commercial and Medicare Advantage claims data, state policies on the medical and recreational cannabis »were not associated with a statistically significant increase in rates of health outcomes related to psychosis," the report states in the study.

In their secondary analysis, the researchers found that the rates of diagnoses related to rates of psychosis have risen slightly among men during the study period, particularly among those aged 55 to 64 and among Asian Americans, in states that allow adult cannabis use, compared with states that do not.

«The results of the fully adjusted models showed that, compared to states with no legalization policies, states with legalization policies did not experience a statistically significant increase in rates of psychosis diagnoses,» the authors write.

The study was conducted by researchers from the University of Philadelphia, Stanford University, and the Palo Alto Veterans Affairs Health Care System.