Negative symptom domain prevalence across diagnostic boundaries: The relevance of diagnostic shifts

Negative symptoms are included in diagnostic manuals as part of criteria for schizophrenia spectrum psychoses only, however some studies have found their presence in other diagnoses. This study sought to clarify negative symptom domain prevalence across diagnostic categories, while investigating whether negative symptoms predicted diagnostic shift over time. Scale for the Assessment of Negative Symptoms (SANS) data were collected at first presentation in 197 individuals presenting with first episode psychosis and again at one year follow-up assessment. Negative symptoms were highest among individuals with schizophrenia and among those whose diagnosis shifted from non-schizophrenia spectrum at baseline to schizophrenia spectrum at follow-up. In a non-schizophrenia spectrum group negative symptoms at baseline were not a significant predictor of diagnostic shift to schizophrenia spectrum diagnoses. The study suggests negative symptoms can present among individuals with non-schizophrenia spectrum diagnoses, although this is most relevant for individuals following diagnostic shift from non-schizophrenia spectrum to schizophrenia spectrum diagnoses. The findings support introduction of a negative symptom dimension when describing a range of psychotic illnesses, and indicate that further research investigating the evolution of negative symptoms in non-schizophrenia diagnoses is needed.