A common example would be ADHD stimulants, where the early stimulating and mood-boosting effects disappear over time while the concentration-enhancing effects mostly remain. This leads a lot of patients to assume the medication isn’t working because it doesn’t feel like those first few doses, which can lead to discontinuation or abuse.
Ketamine has a similar story arc. The antidepressant effect doesn’t require full blown dissociation, but so many headlines and fame-seeking authors have hyped it as “psychedelic medicine” that some patients assume it isn’t working until they disassociate/hallucinate. This can create a sort of nocebo effect where patients may actually be improving but they think they’re not because they didn’t have the wild hallucinations they read about in some exaggerated internet article.