BackgroundFirst-episode psychosis is typically preceded by a prodrome in which there is deterioration in global and social functioningAimsTo examine whether the duration of the prodromal phase influences grey and white matter volumes at the onset of psychosisMethodsEighty-two people were scanned using magnetic resonance imaging when they developed a first episode of psychosis. The duration of the prodromal phase was estimated from detailed interviews and medical records. Voxel-based morphometry was used to assess neuroanatomical abnormalitiesResultsA long prodromal phase was associated with smaller grey matter volumes in the cingulate, frontal and left insular cortex, and with less white matter volume bilaterally in the superior longitudinal and uncinate fasciculi and the cingulumConclusionsThe severity of volumetric abnormalities in first-episode psychosis was greater in those with a long prodrome