[stephengillie]

Is mentally ill doesn't have binary outcomes. Mental issues are set on spectrums (spectra?), usually from normal to extreme or extremely low to extremely high, normal in middle, and each human has an analog value on each spectrum for each disorder. With the latter, we expect a Poisson distribution.

[_delirium]

A particularly tricky aspect for the purposes of this discussion is that the positions on those spectra are somewhat circularly defined when looking at outcomes, at least as defined in the DSM, the most common U.S. diagnostic manual. Many of the conditions have outcome-related diagnostic factors right in the definitions: whether the person is experiencing significant distress in their life, conflict with others or their surroundings, inability to work a job, etc. The pragmatic goal is to avoid over-diagnosing things that aren't actually causing people problems, but as a result it's tricky to isolate causal factors. Even worse if you're diagnosing people in retrospect: of course someone who went on a shooting rampage is going to meet all those criteria, after the fact.

[tunesmith]

Well, yes - I meant it as shorthand for passing a screening test, since that is what they all talk about. Passing a screening test for mental illness will have a lot of false positives, and a lot of false negatives.

"Mentally ill" is one of those mysterious designations, anyway. No one really knows what it means. Is there a set of symptoms such that if you have them, you're definitely mentally ill, and if you don't, you definitely aren't?