Indirect effects from neurological signs to functional outcomes via psychiatric symptoms in Chinese schizophrenia patients

Background: Neurological soft signs (NSS) in motor coordination and sequencing of complex motor acts occur in the majority of schizophrenia patients and are an intrinsic sign of the underlying neural dysfunctions of schizophrenia. The present study explored the longitudinal relationships among NSS, psychiatric symptoms, and functional outcomes in patients with chronic schizophrenia. Methods: The present study recruited a sample of 151 Chinese patients with chronic schizophrenia from a residential care hostel in Hong Kong. The participants completed the Neurological Evaluation Scale for NSS at Time 1, Positive and Negative Syndrome Scale for psychiatric symptoms at Time 1 and Time 2 (3-month follow-up), Activities of Daily Living (ADL) index and Instrumental Activities of Daily Living (IADL) scale for daily functioning at Time 3 (6-month follow-up). Direct and indirect effects of NSS on functional outcomes via psychiatric symptoms were evaluated using path analysis in Mplus 7.2 under bootstrapping. Results: The path model showed an adequate model fit to the data (χ2(38) = 45.11, p = 0.20, CFI = 0.99, TLI = 0.96, RMSEA = 0.04, SRMR = 0.05). Time 1 motor coordination and motor sequencing NSS did not have any significant direct effects on Time 3 functional outcomes in the path model. However, motor coordination NSS exerted significant and negative indirect effects on ADL via positive and disorganized symptoms and on IADL via negative and disorganized symptoms. Discussions: The current results contribute to a better understanding of the determinants of functional outcomes by demonstrating significant indirect pathways from motor coordination NSS to functional outcomes via psychiatric symptoms. The finding that motor sequencing NSS did not affect functional outcomes either directly or indirectly may be explained by their trait marking features