Not distinctly harmless, but No distinct harms?

Research on the harms of talk therapies has recently been increasing. Much of this research aims to measure the prevalence of such harms. The measurement of these harms assumes the ability to distinguish between distinct kinds of harms, e.g., side effects, malpractice effects, nocebo effects, etc. If it were to be shown that - contrary to that assumption - there is no distinction between some of these harms, it would fundamentally challenge this field of work. Or, at least, it would present a significant problem that any future work on talk therapy harms must reckon with. My aim here is to offer such an argument, i.e., that in the context of talk therapies, some of these harms become causally indistinct.