Risk of schizophrenia spectrum disorders among people with HIV: A nationwide, populationbased, matched cohort study

Background: Mental health has become an area of concern among people with HIV (PWH). We aim to assess whether the risk of schizophrenia spectrum disorders (SSD) is increased among PWH. To examine whether such risks are affected by familial factors we also accessed the risk among their siblings. Methods: Nationwide, population-based, matched cohort study of PWH with Danish origin (1995–2021), a comparison cohort from the background population, matched on date of birth and gender, and sibling cohorts. We used cumulative incidence function and Cox regression to estimate absolute risk and hazard ratios (HR) with 95% confidence intervals (CI) of study outcomes and stratified the results according to route of HIV transmission. Findings: We observed an increased risk of SSD among PWH [20-year cumulative incidence 3.7% vs. 1.0% and HR 4.6 (95% CI: 3.8–5.6)], especially among individuals with injection drug use (IDU) as route of HIV transmission [HR 11.3 (95% CI: 7.7–16.4)]. Among siblings increased risk of SSD was mainly observed among siblings of PWH with IDU as route of HIV transmission [HR of 2.9 (95% CI: 1.9–4.5)] and with lack of statistical power among siblings of PWH with men who have sex with men and heterosexual contact as routes of HIV transmission [HR 1.3 (95% CI: 0.9–1.7) and HR 1.2 (95% CI: 0.7–1.9)]. Interpretation: Risk of SSD is substantially increased among PWH, especially among those who report IDU as route of HIV transmission. Familial risk factors might partly contribute to this risk.