Figure 16.8: Results of a classic study of the heritability of schizophrenia The researchers looked for signs of schizophrenia in the biological and adoptive relatives of people who had been adopted at an early age and either did or did not subsequently develop schizophrenia. The results here are the percentage of relatives who showed either schizophrenia or a milder disorder now called schizotypal personality disorder.

(Based on data from Kety et al., 1976.)