A study links migraine headaches, especially if accompanied with nausea or stomach/back pain, to major depressive disorder.
About 10 percent of the population suffers from migraines. Women are more than twice as likely than men to have them. For 4 percent of the U.S. population, the headaches are chronic; that is, they occur more than 15 times a month.The study found that women who had disabling chronic migraines – accompanied by other pain – were 32 times more likely to suffer from major depression than women with infrequent, nondisabling migraines without other severe pain symptoms.
Even women with headaches less than 15 times a month have a tenfold greater risk of major depressive disorder if they rated their headaches disabling and experienced severe pain of other types. (Source: Toledoblade)
I find it interesting to note when different conditions seem (and/or proven to be via study) to be connected. Such as that of diabetes, and depression.