The fact of having a prescription for psychotropic drugs is a knowable thing, albeit jealously guarded by HIPAA and lawsuit-averse manufacturers. Perhaps it is less knowable whether the victims were taking those drugs and had "therapeutic" levels in their systems at time of death.

But it would be extremely unknowable whether or not they had experienced suicidal ideations, and how long they had had them. Because the most you will get is a note in the medical chart, based on a verbal claim by an unreliable narrator.

Then it seems like a pretty terrible idea to just assume they increase the likelihood of social ideation more than they prevent, no?

Tell that to the pharmaceutical manufacturers who ran clinical trials, received guidance from the FDA, and have been required to black-box-label the drugs according to the suicidal ideations which were scientifically proven to increase due to taking the drugs. I don't know where you got "assume"?