Sex therapy (including clinical, licensed sex itself) is a treatment option for sexual health issues - when there are problems and goals pertaining to sex itself.
Sexual health tends to be studied from the angle of being on the 'receiving' end of health, merely being 'improved' as a benefit of good health, or hampered as a result of bad health.
But I wonder whether there have been examples of, any research on, or plausible basis for, sex (whether just orgasm as the common denominator, specific sexual techniques similar to Tantra, and whether solo or with a partner) being a 'medical treatment' mechanism for anything non-sexual in nature also.
In other words, considering the opposite - sex helping to not only improve health itself - but actually be a legitimate and studied field of (alternative) medical treatment for a whole range of scenarios whose goals have nothing to do with sex.
I have no collated research to offer up-front in the question, but only one particular angle of inquiry of my own, which is that sexual activity is part of the parasympathetic nervous system and that, given the involuntary and powerful nature of sexual function, perhaps it might assist in nervous system balance/repair/damage/even issues with PTSD/fight-or-flight sympathetic nervous system issues (e.g. maybe it is the strongest way to activate and train the parasympathetic system where a patient has issues relating to it), if studied.
There are many studies that show sex (and especially intimate sexual activity with a partner) has many direct health benefits, proven mechanisms to relieve mental stress and certainly regulate hormones of the endocrine system which then has further beneficial domino effects itself.
But is there basis to suspect it could do more? (Similar to well-understood exercise and body movement therapies having massive positive and thus often healing effects on the body?) Has this been studied at all?
Obviously in our current society the principal reason for a lack of such study would be the cultural and 'moral' taboos associated with this idea - sex always being an end, but hardly ever a means.