[rincebrain]

Quite.

On average, the acceptable "separated from placebo" margin doesn't have to be that high, but the range of effect is absolutely enormous, even within close relatives.

Antidepressants that did nothing positive or negative for me or some family members were either extremely helpful or extremely harmful to other family members of mine. (Almost never vice-versa; my biochemistry appears to be quite stubborn about responding to a great many classes of treatment, well _or_ poorly, but at least one medication just made me feel completely numb while being extremely helpful to another relative.)

It can also be a weird multidimensional variable in ways many people don't expect - one medication I'm currently taking for depression is 4 pills twice a day (very short half-life), because I was gradually tapering it up. We tried switching to the same manufacturer's single pill that was 4x the dose, twice a day, and immediately I started feeling extremely nauseous whenever in a moving vehicle, which has never happened before. Switch back, problem goes away.

(I know the above sort of outcome is not exclusive to mental health medications, but in my personal experience, I've never had any other medication type vary in outcome based on whether they gave me one or multiple pills adding to the same dosage.)