Investigating Symptom Overlap Between Individuals with High-Functioning Autism Spectrum Disorder and Schizophrenia

Background:  Autism Spectrum Disorders (ASD) and Schizophrenia (SZ) are traditionally conceptualized as separate clinical entities. However, recent findings have suggested that they might overlap, as both are neurodevelopmental disorders characterized by negative affect, reduced social interaction and deficits in social cognition. Importantly, the symptom overlap profile, as defined by standard clinical assessments is not clear.

Objectives:  Compare scores on standard symptom assessments, focusing on positive and negative symptoms as well as social and communication deficits in individuals with high-functioning ASD, SZ and in healthy controls (HC). 

Methods:  29 individuals with ASD, 36 individuals with SZ, and 45 HC ages 18-32 were recruited to date. We administered a battery of clinical assessments to confirm diagnosis and quantify symptoms, including: Structured Clinical Interview for DSM-IV TR (SCID), Positive and Negative Syndrome Scale (PANSS) and the Autism Diagnostic Observation Schedule (ADOS). One way ANOVAs were performed to assess the differences in scores between the groups and correlation analyses to assess the relationship between positive and negative psychotic symptoms and social and communication deficits.

Results: One way ANOVAs showed main effect of group on ADOS Total, Communication (C) and Social Interaction(SI) subscale scores(p <.001). Post-hoc Tukey HSD tests demonstrated that HC showed significantly lower scores than the patient groups with no significant differences between the patient groups on all scores. The PANSS Total score showed a main effect for group (F(1,57)=11.93, p=.001) as did  the subscale  scores(positive, negative and general)(p <.05). However, SZ participants showed significantly higher (worse) scores compared to the ASD group on all PANSS scores.

SZ participants showed a significant correlation between PANSS and ADOS scores, including positive correlations between PANSS Negative and ADOS C, SI and Total scores (r(33) = .494 p =.003, r = .746, p< .001, and r = .71, p <.001, respectively). This group also exhibited a trending inverse correlation between PANSS Positive and ADOS SI and Total (r (34) = -.311, p = .065, r = -.321, p =.056, respectively). Finally, PANSS total scores also showed a correlation with SI (r(33) = .342, p = .044) and a trend with ADOS Total (r = .319) p = .062). 

 ASD participants showed significant correlations between PANSS general and ADOS C, SI and Total scores (r(22) = .410, p = .046, r(22) = .481, p =.017, r(22) = .585. p=.003, respectively). In addition, this group showed a significant correlation between the PANSS total score and the ADOS SI and total (r(22)= .480, p = .018, r(22) - .427, p = .037, respectively). There were no significant correlations between PANSS Negative and ADOS scores.

Conclusions: Our data support the hypothesis that social and communication deficits in SZ are similar to those of ASD. However, the pattern of correlation between these deficits and symptoms related to psychosis, especially negative symptoms, is different between these groups. These results have implications for future research on the underlying biology of both diagnoses as well as to patient assessment in clinical setting in order to fully characterize individual symptoms and their severity.