It has long been known that primary thyroid disorder is associated with mood disorder and vice versa so that the features of major depression can occur in individuals with hypothyroidism. Also, primary depression is often associated with disturbance of the hypothalamic-pituitary-thyroid axis. Roberton's historic description of the relatively common occurrence of postpartum hyperthyroidism eventually led to the discovery that thyroid antibody-positive women are prone to hypothyroidism, which is often preceded by transient hyperthyroidism after delivery. Various aspects of depression and the association with thyroid antibody status are described and the importance of treatment and management of the condition emphasized, particularly in view of the risk of later permanent hypothyroidism in mothers. The effects of associated mood disorder on attachment to the baby, the family, and later development of the child are also described.