[o09rdk]

Some people hallucinate without drugs. There's a range of this, in terms of intensity and type.

Some people take drugs.

They tend to onset around the same age (adolescence to early adulthood).

Ergo, by base rates, some will start around the same time completely by chance.

Also, I get the sense that some hallucinations are "amplifications" of various types of pre-existing sensory experiences. I wouldn't be surprised if some people just started noticing certain things they were doing already but hadn't noticed before.

Not really arguing against the idea/phenomenon of [semi-]permanent drug-induced hallucinations. Just suggesting that it's hard to interpret the data in some cases because of various alternative explanations.