Pretty much any treatment that has very aggressive effects is usually done without it.

Even treatments that can be tested using a control group are quite often tested without it if you can isolate your metrics well enough.

But technically you can still use a control group for psychoactive drugs because in every trial the first rule is not to give the test subjects any information about possible effects or side effects in order not introduce bias, you also quite often isolate the subjects from each other completely.

I'm also not sure if the dose that is given in this case is even high enough to induce hallucinations in the first place.