Factor Analysis of the Scale of Prodromal Symptoms: Differentiating between Negative and Depression Symptoms

Background: This study examines the ability of the Scale of Prodromal Symptoms (SOPS) to differentiate between negative and depression symptoms in a young help-seeking ultrahigh risk (UHR) group. Methods: SOPS data of 77 help-seeking patients at UHR for psychosis were analyzed with an exploratory factor analysis. The extracted Depression factor was validated with the Beck Depression Inventory (BDI). The extracted SOPS Negative symptoms factor was validated with the Negative symptoms subscale of the Positive and Negative Syndrome Scale (PANSS). Results: Four factors were extracted from the SOPS: a negative, depression, disorganized and positive factor. The Negative symptom factor consisted of three items (N1: social anhedonia and withdrawal, N3: decreased expression of emotion; N4: decreased experience of emotions and self), and could be validated with the PANSS Negative symptoms subscale. The Depression factor was also made up of three items (G2: dysphoric mood, G4: impaired tolerance to normal stress, and D4: personal hygiene/social attentiveness), and could be validated with the BDI. Conclusions: Our results suggest that 3 items of the Negative symptoms subscale of the SOPS, 2 items of the General and 1 item of the Disorganization subscale differentiate validly between negative and depression symptoms in an UHR population.