A Tale of three spectra: Basic symptoms in clinical high risk of psychosis vary across autism spectrum disorder, schizotypal personality disorder, and borderline personality disorder

The clinical-high-risk (CHR) approach was developed to prevent psychosis through the detection of psychosis-risk. CHR services are transdiagnostic in nature, therefore the appropriate management of comorbidity is a central part of care. Differential diagnosis is particularly challenging across three common comorbidities, schizotypal personality disorder (SPD), autism spectrum disorder (ASD), and borderline personality disorder (BPD). Phenomenological research indicates a disturbance of ‘basic self’ may differentiate between these commonly comorbid disorders and can be captured by Huber’s basic symptoms (BS) concept. We investigated whether BS vary across these disorders and may inform differential diagnosis in young person’s meeting CHR criteria. 685 participants meeting CHR criteria from the NAPLS-3 cohort completed the COGDIS items of the schizophrenia proneness instrument, a measure of BS, as well as the structured interview for DSM-5 (SCID-5). A Logistic regression model was used to investigate the variation of COGDIS across SPD, ASD, and BPD, whilst controlling for age and SIPs positive severity. Meeting COGDIS criteria was positively associated with SPD (OR = 1.72, CI=[1.31-2.28], p=0.001) but not ASD nor BPD. Our results indicate that ‘basic self-disturbance’ as indicated by COGDIS differs across SPD, ASD, and BPD. COGDIS may be useful to inform the management of comorbidities in CHR services, by providing insight into subtle subjective experiences that may benefit from disorder-specific interventions.