I too have drug-induced psychosis (probably). My symptoms went on for 2 years, then went away. I had a "relapse" after smoking some cannabis and stuff about 8 months after that. I had small bouts of mild psychosis 1 or 2 times before the first major break though, so I guess that means 3-4 times. I also had some worsening of symptoms during that first break whilst using drugs, but nothing I'd call a relapse really as they only lasted a day or so.

Currently we are waiting to see if I relapse or not without drugs. If so, then I'll have some underlying condition but drugs will have only been the trigger. I don't think that's likely though.

The only real advice I can give is, your brain will be still be in a very delicate balance so using drugs again is not a good idea. If you are fully committed to recovery, then ideally you should never use drugs again.. (basically where I've got myself to, after making the mistake of thinking I could use them even moderately)