The connection between birth order and the incidence of schizophrenia is directly relevant to the problem of the etiology of the disease.1,11 The absence of any clearly established relationship between the two has been cited as support for the belief that environmental factors play at most a relatively minor role in the disease process.7
The question of relationship between birth order and schizophrenia has been revived by recently published experimental findings with normals. These studies suggest a relationship between birth order and a primary symptom of schizophrenia, social self-isolation. The work done by Schachter10 indicates that subjects who are first-born or only children tend to be more affiliative in an anxiety-provoking experimental situation than those who have older siblings. Laterborn subjects when anxious did not particularly wish to be with other people. Schachter saw this tendency to prefer isolation