A. Any headache fulfilling criterion C
B. Major depressive disorder (single episode or recurrent) or persistent depressive disorder has been diagnosed according to DSM-5 criteria
C. Headache occurs exclusively during depressive episodes
D. Not better accounted for by another ICHD-3 diagnosis.
Many antidepressants, especially tricyclic antidepressants, are effective against headache disorders even when depression is not present. This makes it difficult to determine whether remission of or improvement in a headache disorder associated with depression and treated with a tricyclic antidepressant is, in fact, evidence of causation. Remission of headache is more suggestive of a psychiatric cause when a major depressive disorder improves under treatment with other type of antidepressants shown to be less effective in headache treatment.