Psychopathic Traits Associate With Later Schizophrenia

Despite well-known diagnostic and neurobiological overlaps between psychopathic traits and schizophrenia, it has remained unclear whether psychopathic traits increase the risk for later schizophrenia. Former studies have proven only a weak correlation between psychopathy and DSM axis I diagnoses.

We combined data from individuals who underwent forensic psychiatric evaluations (FPEs) at Niuvanniemi Hospital between 1984 and 1993 with the records from the Care Register for Health Care to examine the relationship between psychopathic traits, measured by the Psychopathy Checklist-Revised (PCL-R), and the development of schizophrenia following the evaluation. We conducted survival analyses using Kaplan-Meier estimates and Cox proportional hazards models, with a follow-up period of up to 40 years. Mortality data were obtained from the National Death Registry. Statistical analyses were adjusted for age, sex, criminal responsibility, and substance abuse disorder at the time of the FPE.

The study included 341 individuals (278 males [81.51%] and 63 females [18.49%], mean [SD] age 33.52 [11.49]) who were adults, criminally responsible, and did not have a psychotic illness, severe mental disability, or brain damage at FPE. Compared to individuals with total PCL-R scores less than or equal to 10, those with scores of 11-24 (adjusted hazard ratio [aHR] = 5.30, 95% CI = 1.21-23.25) and 25 or higher (aHR = 9.33, 95% CI = 2.04-42.76) had a significantly higher risk of later hospitalization due to schizophrenia. Also, individuals classified as psychopathic (PCL-R ≥ 25) had a significantly higher risk of developing schizophrenia compared with those classified as non-psychopathic (PCL-R < 25): aHR = 2.37, 95% CI =1.17-4.80. A total of 20% of psychopaths developed schizophrenia over the follow-up.

The novel results suggest that there is a link between higher PCL-R scores and a higher risk of later-life schizophrenia outbreak among non-psychotic individuals undergoing FPE. Multiple factors can explain the finding, including substance use and mutual risk factors.