Research published in American Journal of Psychiatry indicated that substance-induced psychotic disorder occurred in people at high familial risk for drug and alcohol abuse and a moderate familial vulnerability to psychosis.
“Clarifying the etiology of substance-induced psychotic disorder is of interest because it can provide insights generalizable to other psychotic syndromes,” Kenneth S. Kendler, MD, of the Virginia Institute for Psychiatric and Behavioral Genetics and the department of psychiatry, Virginia Commonwealth University, and colleagues wrote.
Using data from the Swedish national registries, the investigators examined people with a substance-induced psychotic disorder diagnosed between 1997 and 2015 (n = 7,606). Participants were followed up for an average of 84 months. They analyzed data on first- through third-degree relatives to determine a familial risk score for nonaffective psychosis, drug abuse and alcohol use disorder. The main analysis focused on calculating the cumulative hazard for schizophrenia for different substance-induced psychotic disorder types.
Swedish individuals with substance-induced psychotic disorder showed large increases in standardized familial risk scores for drug abuse (+1.09; 95% CI, 1.02-1.15) and alcohol use disorder (+0.98; 95% CI, 0.93-1.03) as well as modest increases in familial risk scores for nonaffective psychosis (+0.35; 95% CI, 0.3-0.41), according to the results.
In the sample, the cumulative risk for progression to schizophrenia was 11.3%; the data showed that those with alcohol-induced psychotic disorders were at lowest risk for schizophrenia while those with cannabis-induced psychotic disorder were at highest risk.
Predictors of progression to schizophrenia included early age at diagnosis of substance-induced psychotic disorder, male sex and further episodes of drug abuse, alcohol use disorder and substance-induced psychotic disorder.
Using a risk prediction model, the researchers found that 47% of individuals who developed schizophrenia were in the upper two deciles of risk.
Although familial risk scores for drug abuse and alcohol use disorder did not significantly distinguish individuals who converted to schizophrenia from those who did not, familial risk score for nonaffective psychosis did (0.67; 95% CI, 0.4-0.95 vs. 0.33; 95% CI, 0.28-0.39). In addition, familial risk scores for nonaffective psychosis were indistinguishable between people with schizophrenia with and without previous substance-induced psychosis.
“Substance-induced psychotic disorder likely arises from both substantial drug exposure and elevated liability to psychosis,” Kendler and colleagues wrote. “Schizophrenia following substance-induced psychotic disorder is better explained as a drug-precipitated disorder in highly vulnerable individuals rather than as a syndrome predominantly caused by drug exposure.” – by Savannah Demko
Disclosure: The authors report no relevant financial disclosures.