In my case, when I've done dangerous, yes very much a nanosecond of madness. I suffer from intrusive thoughts, they go round and round in my head "swallow razor blades" or "take the pills" and it get's very draining. Before I started receiving psychiatric help my only respite from those thoughts was to give in. Immediately after I'd given in I knew I was in trouble and had to seek medical treatment and the thoughts had stop. In regards to what psychiatric help you receive after A+E in my area you'll have a follow up appointment with a psych nurse and that's it. Unfortunately I'd tortured mself in quite a few cruel and unusual ways before I got passed on to the CMHT. That said now I'm under them the help and support I've received has been fantastic and I've learnt to deal with my feelings without recoursing to such self-destructive acts. It's just a shame that services are so stretched that many who need the help don't access it.