That's not ADHD, Cannabis. Here in America, our Diagnostic and Statistical Manual for mental stuff calls that "Intermittent explosive disorder." It's basically just bouts of rage that aren't a reaction that's really in proportion to what's happening. I've heard people also term it "rage-a-holic," at least when someone has a lot of episodes of it. It's serious when it's bad because people can really harm others they like or love--or can harm property. Intermittent explosive folks can really get themselves into legal trouble, too. From what I've read Lip describe about his temper, he has this, too. It often happens to people who had parent who tended to have fits of rage and violent abusiveness, both verbal or physical. Often the parent who modeled it also has drug or alcohol addiction, too.
Intermittent explosive disorder - MayoClinic.com