The Clinical Significance of Sub-Threshold Psychosis in the General Population: Comorbidity and Suicide Risk

Background and Purpose: The general population prevalence of psychotic disorders is far exceeded by that of sub-clinical psychotic-like experiences, which are phenomenologically similar to threshold psychosis but of less intensity or associated impairment. Psychotic-like experiences often occur in the context of common mental disorders, where they are associated in adolescents with greater severity, earlier onset, and greater need for treatment. Psychotic-like experiences are also strongly associated with suicidal ideation and behavior in adolescents. It is not known whether psychotic-like experiences continue to be associated with comorbidity of common disorders or with suicidality in adulthood. The first aim of this study is to examine the prevalence of psychotic-like experiences among respondents with common mental disorders, and to describe the clinical significance of these symptoms when occurring in the context of common mental disorders. The second aim is to determine the risk for suicidal ideation and behaviors among respondents with psychotic-like experiences.

Method: Data from the Collaborative Psychiatric Epidemiology Surveys (n=20,013) were used to examine psychiatric comorbidity and suicidality among adults who reported psychotic-like experiences.  Presence of psychotic-like experiences and mental health disorders was determined using the World Health Organization Composite International Diagnostic Interview. Odds ratios with 95% confidence intervals (OR, 95% CI) were calculated for associations between psychotic-like experiences and common mental disorders (affective, anxiety, and substance use disorders) and suicidal behaviors (ideation, plans, and attempts). All odds ratios were adjusted for demographic factors, with significance of individual predictors tested using Wald chi-square tests.

Results:  Within this nationally-representative data set, 6.6% of all respondents endorsed lifetime psychotic-like experiences and 2.4% reported psychotic-like experiences over the prior 12-months. All classes of common mental disorders were more than twice as prevalent among individuals reporting psychotic-like experiences, whether using 12-month or lifetime diagnoses. Further, risk for psychotic-like experiences increased in a dose-response relationship with increasing number of comorbid conditions such that those with three or more mental health conditions had 12-fold greater odds of experiencing psychotic-like experiences over the concurrent 12-month period (OR = 12.3, 95% CI = 3.3-45.3). Twelve-month psychotic-like experiences were also associated with greatly increased odds for suicidal ideation (OR = 5.5, 95% CI = 3.3-9.2), suicide plans (OR = 4.4, 95% CI = 2.2-8.9), and suicide attempts (OR = 10.2, 95% CI = 4.4-23.3) over the same year, particularly if psychotic-like experiences included sub-threshold delusions that one’s mind was being controlled by strange forces (OR = 14.8, 95% CI = 3.1-70.5).

Conclusions and Implications: This study presents evidence that psychotic-like experiences are clinically meaningful despite not meeting full criteria for threshold psychotic disorder. They appear to be indicators of general mental health difficulties and comorbidity of common mental disorders, and may be particularly important as markers of suicide risk. Future studies should examine whether there is a causal relationship between psychotic-like experiences and suicidality, or if they are simply useful risk indicators. Regardless, social work practice may benefit by assessing and screening for psychotic-like experiences in high-risk mental health clients, particularly those with multiple comorbidities or elevated risk for suicide.