Risk factors, pre-morbid functioning and episode correlates of neurological soft signs in drug-naive patients with schizophrenia-spectrum disorders

Abstract

Background: There is a lack of consistent evidence regarding associations of neurological soft signs (NSS) with illness-related variables in schizophrenia. This study examined NSS in first-episode psychotic patients with respect to their factor structure and associations with risk factors, pre-morbid characteristics, psychopathology and spontaneous extrapyramidal syndromes.

Method: First-episode, drug-naive patients with schizophrenia-spectrum disorders (n=177) were assessed for NSS using the Neurological Evaluation Scale, and its 26 constituting items were factor analysed. The identified neurological dimensions were then entered into hierarchical regression models as outcome dependent variables of a set of predictors including risk factors (familial loading for schizophrenia, obstetric complications), pre-morbid characteristics (neurodevelopmental delay, symptoms of attention deficit-hyperactivity disorder, pre-morbid functioning), psychopathological domains (reality distortion, disorganization, negative symptoms, mania, depression, catatonia) and spontaneous extrapyramidal syndromes (parkinsonism, dyskinesia, akathisia).

Results: Five neurological domains were identified: sequencing, release signs, sensory integration, abnormal movements and coordination. Multivariate analyses showed independent associations (p<0.01) of sequencing with familial liability to schizophrenia, deterioration of pre-morbid adjustment and parkinsonism; release signs with obstetric complications, catatonic symptoms and parkinsonism; sensory integration with familial liability to schizophrenia; abnormal movements with familial liability to schizophrenia, obstetric complications, parkinsonism and dyskinesia; and coordination with neurodevelopmental delay. The empirically derived factors explained additional variance over and above that explained by subscale scores across the examined variables.

Conclusions: Familial liability to schizophrenia, obstetric complications, neurodevelopmental delay, deterioration in pre-morbid functioning and observable motor disorders appear to contribute independently to domains of neurological dysfunction. The findings support a neurodevelopmental model of NSS in schizophrenia.