The major disorders of the brain (MDBs), in terms of their prevalence and the burdens of ill health, disability and financial cost that they impose on individuals and society, are headache, depression and anxiety [1-4]. Tension-type headache (TTH) and migraine are the second and third most prevalent disorders in the world [5], and migraine is the seventh highest specific cause of years of life lost to disability (YLDs) [5,6]. Major depressive and anxiety disorders are not as prevalent, but still common, and they contribute even more to disability at societal level: respectively they are the second and sixth leading specific causes of YLDs [5,7].