The notion of causation in psychiatry may seem daunting at first. In many cases, there are multiple causes, or, at least, the effects of many causes appear to overlap.
Alternatively, we may look at this phenomena as the presence of a precipitatnt and a susceptibility.
At one time, the term 'diasthesis" was used to describe such a susceptability. But it is difficult to say, in a patient with a compound of specific substance dependences (such as, say, dependence on alcohol, nicotine, and cocaine) the presence of a diasthesis is more than that -- it indicates the susceptibility is the primary mechanism by which the occurence of the different manifestations of illness are occuring.
Thus, any classication of etiology needs to look at the former, rather than the latter.