The unequal sex ratio for several of the classes of mental disorders could be due to various methodological factors including ascertainment biases, differential reporting or recognition by males and females or factors associated with assessments that preferentially identify symptoms/disorders by sex. Ascertainment biases in clinical samples in psychiatry have been well‐recognized, 25 and the large‐scale community surveys of both adults and children have showed biases in severity and comorbidity of clinical samples, and under‐or‐over‐representation by sex. Artifactual differences could also be due to misclassification based on symptom presentation or severity, and social or cultural differences in the recognition and interpretation of symptoms. For example, the higher rate of hyperactivity symptoms in males noted above may contribute to the higher rate of ADHD diagnoses in males. A longitudinal cohort study that tracks sex‐specific incidence throughout the period of risk in a community based or high‐risk sample would be one approach to test whether the deviant sex ratio for a particular disorder is a result of sampling or diagnosis. For example, depressive symptoms present equally in boys and girls in childhood, and
