In the last post I discussed thoughts on why certain groupings of physiological measurements may turn out to be a better predictor of suicidal behavior than genes (check out that post here). On top of that, I have some general ideas as to how this may play out.
I would imagine that each psychological disorder may end up having its own constellation of physiological factors with predictive power. For instance, people with major depression without psychotic features would have a different constellation of physiological factors associated with suicidal behavior than people with schizophrenia. The people in the major depression group may have lots of indicators of very low mood but a certain amount of anxiety / excitement too. Currently, it is a commonly held belief among clinicians, researchers, and even the general public that a certain amount of energy is required to make a suicide attempt. Rather than a 1 to 1 correlation between low mood and suicide - i.e. the people w/ the lowest mood are at the highest risk of making an attempt - low mood plus a certain amount of motivation/excitation to attempt is believed to be in the mix. It's worth noting that the excitation wouldn't necessarily improve one's mood. Low mood and excitation are not only likely to be separate and valid psychological constructs, but they would represent themselves differently physiological tests. Speaking in terms of totally made up units of measurement to illustrate a point, a person with major depression may need lower than -100 endorphins (representing low mood) and somewhere between +15 and +30 cortisol (representing excitation) in order to qualify as being at imminent risk for suicide. On the other hand, a person with schizophrenia may need lower than only -25 endorphins (representing low mood) and higher than +200 cortisol (representing excitation) to be at imminent risk for suicide attempt. Continuing down the path of this totally fabricated example, high levels of excitation may be more indicative of imminent suicide risk in schizophrenia than in major depression for a couple of reasons. If someone with schizophrenia attempts suicide, it has a decent likelihood of being because they heard a voice in their head commanding them to do so. As such, the experience of hearing a scary voice telling them to kill themselves would hypothetically induce a physiologically state of excitation. On the other hand, a relatively low but existent amount of excitation would hypothetically be required for a person with major depressive disorder to attempt suicide. Concurrently, their mood would presently need to be extremely low to be at risk for such destructive behavior.
Pulling back out of the examples and towards the larger picture, in short, I would imagine that each disorder would have it's own set of physiological risk factors. Major depression, schizophrenia, bipolar, borderline personality disorder, etc. would all have different high-risk constellations. Some more thoughts on the specifics to come.