These data show that smaller hippocampal volumes are present from the onset of illness. While these findings would support the neurodevelopmental model of schizophrenia, the finding of smaller left hippocampal volume in patients with first-episode schizophrenia and affective psychosis does not support the prediction that smaller hippocampi are specific to schizophrenia. The association of smaller right hippocampal volumes with increased illness duration in chronic schizophrenia suggests either that there is further neurodegeneration after illness onset or that bilateral small hippocampi predict chronicity.

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These findings suggest that impairment of olfactory identification is a premorbid marker of transition to schizophrenia, but it is not predictive of psychotic illness more generally.

Impairment in olfactory identification ability was apparent from the outset of psychotic illness and was not specific to schizophrenia or schizophreniform disorder. No change in the degree of this deficit was found after patients were stabilized and had responded to medication. The deficit could not be explained by peripheral factors that might contribute to olfactory identification ability, suggesting that it reflects central mechanisms.