February 14, 2020
1 min read

Infections linked to substance-induced psychosis, schizophrenia

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Carsten Hjorthøj

Severe infections may increase the risk for developing substance-induced psychosis, according to a study conducted in Denmark and published in American Journal of Psychiatry.

“Infections play an important role in psychotic disorders even in this type of psychosis in which it would otherwise seem straightforward to just say that the psychosis is simply caused by use of substances,” Carsten Hjorthøj, PhD, of the Copenhagen Research Center for Mental Health, told Healio Psychiatry.

The researchers noted that previous research has suggested that schizophrenia likely has an immune-related component; however, no prior research examined whether substance-induced psychosis may also have this component. To address this research gap, they collected data from the combined nationwide Danish registers to include all people born in Denmark since 1981. They estimated hazard ratios and confidence intervals using Cox proportional hazards regression with infections as time-varying covariates, and they operationalized infections both as any infection and by the site of infection.

Of the 2,256,779 individuals included, Hjorthøj and colleagues recorded 3,618 cases of incident substance-induced psychosis. Any infection increased the risk for substance-induced psychosis (HR = 1.3; 95% CI, 1.22-1.39), with the risk doubling for the first 2 years. The infection most strongly associated with substance-induced psychosis was hepatitis (HR = 3.42; 95% CI, 2.47-4.74). Different types of substance-induced psychosis were associated with different types of infections, and after controlling for potential confounders, such as substance use disorders, most associations remained significant. The researchers noted that only hepatitis predicted conversion to schizophrenia after substance-induced psychosis (HR = 1.87; 95% CI, 1.07-3.26).

“The clinical relevance is perhaps still a bit downstream, in that we don’t yet fully understand how infections or immunological responses eventually manifest as psychosis," Hjorthøj said. "With further research, this study and related studies could open the door to novel treatments for psychotic disorders. There is already some evidence that immunotherapy and anti-infectious agents may be effective for treating some people with psychosis and, with more research, it may become possible to prevent the emergence of psychosis altogether." – by Joe Gramigna

Disclosures: The authors report no relevant financial disclosures.