Yep I have definitely experienced this (although I have not had outbursts for many many years). I assumed it was anxiety, but the negative tone of the thoughts is the depression.

Whats on your mind? What kind of thoughts? Does writing them down help at all? Lately I have been having a lot of success with postponing my worrying thoughts. It is hard work to constantly put thoughts off, as I throw one out a new one replaces it, but eventually I start to fall asleep. Sometimes I will recognise I am falling asleep as I am fighting the thoughts and naturally I relax because I know sleep is coming. These thoughts are the root of irritability and if you combat them you will combat the rest of the symptoms.