Direct comparison of first-contact <i>versus</i> longitudinal register-based case finding in the same population: early evidence that the incidence of schizophrenia may be three times higher than commonly reported

Abstract

The incidence of schizophrenia was three times higher in a longitudinal register study than in a high-quality first-contact study conducted in the same population. Risk estimates based only on first-contact studies may have been affected by selection bias.