depression
"Miracle drug for me. I had a very bad reaction to SSRIs (hospitalised for some days) and amitriptyline (couldn't stop sleeping) before my GP suggested we try mirtazapine for my mood and migraine management. 

I started on 15mg. My migraines were unchanged (now managed by topimarate), but my mood has improved a thousandfold - while formerly I was very much reclusive, self-loathing, and suicidal, I can now leave my flat and socialise! My college grades are back up to standard, and I've found myself generally enjoying life. Overall a huge improvement - still a way to go, but having just upped my dose to 30mg the future seems bright.

Side effects are minimal - I sleep much better now. Avoid alcohol though, it doesn't mix too well with the pills."