General population studies suggest a non-casual association (comorbidity) between migraine, major depression and anxiety disorders (panic attack disorder, obsessive-compulsive disorder, generalised anxiety disorder). The risk of developing affective and anxiety disorders is not increased uniformly in the different migraine subtypes, but it is more elevated in migraine with aura patients. The relationship between migraine and depression is "bi-directional" (i. e., migraineurs have a more than three-fold risk of developing depression compared with non-migraine patients, while depression patients that have never suffered from migraine before have a more than three-fold risk of developing migraine compared with nondepressed patients) and specific (i. e., the presence of migraine or severe non-migraine headache increases a patient's risk of developing depression or panic attack disorder, whereas the presence of depression or panic attack disorder is associated with a greater risk of developing migraine, but not severe non-migraine headache). Comorbidity with psychiatric disorders has also been described for chronic tension-type headache and for chronic daily headache, although these findings are based only on clinical population data.