Understanding the inverse relationship between age and psychotic symptoms: The role of borderline personality traits

There is a well-established inverse relationship between age and positive psychotic symptoms, both in patients with psychotic disorders and in general population samples with psychotic experiences. The reason for this inverse relationship is unclear. We hypothesized that life-course developmental changes in borderline personality traits, which also typically decline with age, might explain the inverse relationship between age and positive psychotic symptoms.

We tested this hypothesis with data from 19,980 adults who completed 2000, 2007, and 2014 UK Adult Psychiatric Morbidity Survey studies. Hallucinations and delusions were assessed with the Psychosis Screening Questionnaire. Borderline features were assessed with the Structured Clinical Interview for DSM-IV Axis II Personality Disorders Screening Questionnaire. Logistic regression models with effect decompositions were used to conduct the analyses.

As expected, age was negatively associated with hallucinations and delusions. These effects were wholly or mostly reduced after controlling for borderline features. Similar results were found in a subgroup of participants with a probable psychotic disorder. Repeating the analysis with a broad index of psychopathology severity instead of borderline features did not produce comparable results. Borderline factor scores reflecting identity/relationship disturbance, mood instability/anger, and self-harm/suicidality were created, all of which appeared to explain part of the inverse relationship between age and psychotic experiences.

Declining borderline traits throughout adulthood may account for the reduced prevalence of positive psychotic symptoms in both clinical and non-clinical populations. Future research might evaluate the impact of treatments that target borderline traits on positive psychotic symptoms.