Clinical evaluation of functional capacity in treatment resistant schizophrenia patients: Comparison and differences with non-resistant schizophrenia patients

Treatment resistant schizophrenia (TRS) is defined by poor or non-response to conventional antipsychotic agents. Functional capacity is defined as the baseline potential of a patient to function in the community, irrespective of actual achievements gained, and has never been studied in TRS. Here, we screened 182 patients with psychotic symptoms and separated them in TRS (n = 28) and non-TRS (n = 32) ones, to evaluate whether they exhibited differential extents and predictive clinical variables of functional capacity. Functional capacity was measured by the UCSD Performance-Based Skills Assessment (UPSA). Psychotic symptoms by PANSS, social functioning by PSP and SLOF, clinical severity of the illness, cognitive functioning, and neurological soft signs (NSS) were assessed. TRS patients had non-significant lower UPSA scores compared to non-TRS (t-test: p > 0.05). In TRS, UPSA score correlated with multiple clinical variables. The highest effect sizes were observed for PANSS negative score (r = -0.67, p < 0.005); SLOF Area1 score (r = 0.66, p < 0.005); NSS severity (r = -0.61, p < 0.005). Multivariate analysis showed that main predictors of UPSA score in TRS patients were PANSS negative score, education years, NSS, Problem Solving performances, and PSP score (F = 11.12, R² = 0.75, p < 0.0005). These variables were not predictive of UPSA score in non-TRS patients. Hierarchical analysis found that variance in UPSA score mainly depended on negative symptoms, NSS, and problem solving (F = 15.21, R² = 0.65, p < 0.0005). Path analysis individuated two separate paths to UPSA score. These results delineate a limited and independent group of candidate predictors to be putatively accounted for therapeutic interventions to improve functional capacity, and possibly social functioning, in TRS patients.