Are there neurological and sensory risk factors for schizophrenia?

The association between left-handedness, epilepsy, and hearing impairment with schizophrenia was investigated using data from a cohort of 50,000 male Swedish conscripts linked to the Swedish National Register of Psychiatric Care. Though epilepsy was rare in this cohort, no association with schizophrenia was found. Left-handedness was associated with neither schizophrenia nor other psychoses. The study shows that, when studied from a population base, the apparent increase in neurodevelopmental anomalies in schizophrenia may be an artefact of bias. However, schizophrenia was 1.81 (95% CI 1.2-2.7) times higher amongst those with severe hearing loss, which may be preventable.