Many of the classifications of psychological types have been discarded and rearranged under the purely behavioural approach adopted by current psychiatry, as expressed in the Diagnostic Statistical Manual, fifth edition (DSM5).
Causation has been much less of a preoccupation of the profession under behaviourism although the development of cerebral scanning devices, such as Functional Magnetic Resonance Imaging (fMRI) has shed more light on the subject.
Therapies have usually been developed by trials, based on theoretical constructs, and have been found to be more or less helpful without the reasons for such effects necessarily being known.
The commonest malady has always been depression, which is typified by a lack of motivation to engage in activities of life which the person would usually find gratifying or routine. My experience, without having been subject to chronic depression but rather episodic as a result of circumstances, is that the state is a result of feeling overwhelmed by conflicting motivations or feelings of obligation which result in a lack of clear direction and a subsequent state of withdrawal.
The tendency to consign all psychological states to behavioural definitions ignores simple causation and can result in recourse to treatments which are inappropriate. Treatment should provide for the neuropsychological nature of the individual subject.and not be oriented only towards conformity to social norms.
In the cases of those on the autistic spectrum, relief of the sense of imperative in all the factors contributing to the depressive condition would be more effective. The underlying reality is that depression in these cases is not as result of predisposition but of identifiable pressures which should be amenable to a more sympathetic regime of treatment, based not only on background and experiences but on the prevailing circumstances affecting the child or adult person. In other words, removal of conflicting factors which contribute to