Age at onset in Canadian Schizophrenia patients: Admixture analysis

Despite considerable amount of data from several studies, none of the thresholds used to define age at onset (AAO) in schizophrenia have been validated. The aim of this study is to assess the presence of different homogenous subgroups in schizophrenics based on the age at onset. Admixture analysis was applied to identify model(s) of separate normal distributions of AAO characterized by different means, variances and population proportions. This helped us in identifying different subgroups in our sample of 440 schizophrenia patients.

The model that best fits the observed AAO distribution was a mixture of two Gaussian distributions with an ideal cut-off point. The mean ages estimated in this model were 18.01years (SD=2.46) and 26.07years (SD=8.11). The cut-off point was 22years.

These results suggest the existence of two homogeneous subgroups in schizophrenia patients. This may have important implications for searching schizophrenia susceptibility factors.