Hi karen,

First it is important to get an accurate diagosis from a doctor whether or not you do suffer from depression. Some people who have Migraine disease also suffer from other comorbid conditions, they occur together but are not caused by one another. Depression, thyroid issues and bi-polar are a few. This article has useful information for you: Migraine Disease and Bipolar Disorder, a Link. You may want to talk to your primary care doctor first for an evaluation.

Now, onto Amerge. It's not that the triptans like Amerge raise your serontonin levels, they  seem to work to by targeting the nerves and blood vessels thought to trigger a Migraine attack-block certain receptors that may trigger an attack all while there is a tiny bit of vasoconstriction going on to abort the attack. (This is in very laymans terms as I undertsand it)

Antidepressants, Triptans, and Serotonin Syndrome may give you some insight  to your question on serotonin. But the most important part of this article is below:

"The FDA has reviewed 27 reports of serotonin syndrome. In 13 cases, the patients were hospitalized. Two cases were considered to be life threatening.This advisory is neither totally new information nor any reason to panic if you are currently taking this medication combination. Triptans already carry a warning in their prescribing information warning of possible problems when also taking antidepressants. Serotonin syndrome, although potentially fatal, is not common. If you are concerned about your medications, contact your physician."
  

I hope this helps,

Nancy