Secular Changes in Affective Disorder and Variations in the Psychosis Gene

To the Editor.—  Two surveys have reached the surprising conclusion that there has been a recent secular increase in the prevalence of affective disorder. The Yale University—National Institute of Mental Health Collaborative Study¹ of 1482 first-degree relatives of 90 bipolar I and 163 major depression probands reported a "large secular increase in affective illness over the past three generations." The National Institute of Mental Health—Clinical Research Branch Collaborative Program on the Psychobiology of Depression Clinical Study² of 2289 first-degree relatives of 523 probands with affective disorder reported "a progressive increase in rates of depression in successive birth cohorts through the 20th century and an earlier age of onset of depression in each birth cohort." Both studies were carried out with standardized criteria and with care to exclude artifacts of ascertainment. Neither group of authors offered a confident explanation for the findings.I wish to suggest an explanation that