Are adult development and the course of mental disorder related to each other in major ways, or are they mutually irrelevant? Polar opposite views have dominated this issue. From the beginning of modern psychiatry in the nineteenth century, two major theories of the course of mental disorders, the psychoanalytic and the natural history theories, have upheld opposite extremes. The natural history view has suggested that any mental disorder, like any other type of disease, has a natural history, so that developmental considerations are essentially irrelevant to course. In fact, this model states that a disorder or disease process is defined by its course, and that course is what establishes the disease as a diagnostic entity. Thus, for example, in describing dementia praecox – later called the group of schizophrenias by Bleuler (1911/ 1950) – Kraepelin brought together three rather different syndromes under one diagnostic entity because he believed that they each had a deteriorating course and outcome (Kraepelin, 1902).

In contrast to that approach, the psychoanalytic orientation has suggested that the course of a mental disorder is intimately tied to psychological developmental mechanisms. In this view, the course of a psychosis, for example, has been perceived as the result of the degree to which id, ego, and superego pressures and mechanisms can be reconciled, which in turn is a function of their developmentally influenced strengths and patterns of functioning (Freud, 1924).

In this chapter we shall review briefly some recent major trends in understanding the course of mental disorders and adult aspects of development suggesting that these two domains are neither identical nor totally unrelated.