Factor Structure of the Scale of Prodromal Symptoms and Empirical Development of a Brief Version in Youth at High Risk for Schizophrenia

Background:  Limited research has been performed to track prodromal symptoms in individuals with familial high risk youth, a population which is at an increased possibility of developing psychosis. There has also never been a brief version of the SOPS, a measure which is lengthy to administer in it’s entirety. Exploration of a brief tool that could predict psychosis is imperative for  these high risk youth.

Methods: One hundred and one high risk (HR) individuals with a first or second degree family member living with either schizophrenia or schizoaffective disorder were included in this study. Prodromal symptoms were assessed by trained interviewers through the Structured Interview for Prodromal Syndromes (SIPS) using the Scale of Prodromal Symptoms (SOPS). These individuals were assessed at study entry and then yearly for up to 3 years (averaging 1.37 years).  A series of exploratory factor analyses were used to examine the relationship between items.

 Results: Results of a two-factor solution separated items between Positive Symptoms/Functional Impairment and Disorganization/Thought Disturbance. We proceeded to examine the possibility of constructing a brief version of the SOPS based on the items with the highest factor loadings. The relationship between the B-SOPS and the total scale was evaluated to examine the convergent of the B-SOPS, using Pearson correlation analysis and was found to be correlated highly at r = .92. The B-SOPS was shown to be significant in predicting the development of psychosis; for every 1 point elevation on the B-SOPS, individuals were 1.69 times more likely to develop psychosis at follow up. Convergent validity was evaluated by examining the relationship of the B-SOPS to the GAS at baseline (r = -.65, p < .001, N = 92) and then again at follow up (r = -.50, p < .001, N = 61).

 Conclusion and Implications: Our findings showed that a two factor solution separated items on the SOPS between Positive Symptoms/Functional Impairment and Disorganization/Thought Disturbance and that the B-SOPS is a significant tool in predicting the development of psychosis among youth at familial high-risk for psychosis. Numerous studies have been done in an attempt to predict psychosis but few have been completed with familial high risk youth. A brief version of the SOPS could be administered easily to this population to assess for risk of developing psychosis.