The trajectories and correlates of two negative symptom subdomains in first-episode schizophrenia

Background Recent studies suggest a two-factor structure for negative symptoms as assessed by the Positive and Negative Syndrome Scale (PANSS) in schizophrenia, namely experiential and expressive subdomains. Little is known about their clinical correlates and treatment trajectories. Objectives We sought to replicate the two factor-analysis derived subdomains for PANSS negative symptoms in schizophrenia and to assess their independent demographic, premorbid and treatment-related characteristics. Methods This was a longitudinal study of 106 minimally treated participants with a first episode of a schizophrenia spectrum disorder who received treatment with flupenthixol decanoate 2-weekly injections over two years. Factor analysis was used to characterize the PANSS negative symptom subdomains and linear mixed-effect models for continuous repeated measures were constructed to assess the temporal relations between the negative symptom subdomains and premorbid and treatment related variables. Results Factor analysis confirmed a two-factor solution for experiential and expressive subdomains of negative symptoms, although they were strongly correlated. The treatment response trajectories for the two subdomains did not differ significantly, and neither subdomain was significantly associated with our premorbid variables. We found significant main effects for disorganised symptoms and extrapyramidal symptoms on the expressive subdomain, and for disorganised symptoms and depressive symptoms on the experiential subdomain. Post-hoc testing indicated that reductions in HDL-cholesterol levels were associated with less improvement in both expressive and experiential subdomain scores. Conclusion The two negative symptom subdomains are closely related, have similar premorbid correlates and respond similarly to antipsychotic treatment. Depression affects the experiential subdomain, whereas extrapyramidal symptoms affect the expressive subdomain.