Introduction

Since Leonhard (1979) originally proposed the distinction between bipolar and monopolar (unipolar) forms of affective disorder, there have been many attempts to validate this separation (Angst 1966; Perris 1966; Perris 1990; Perris 1992). In particular, there has been considerable interest in identifying pathophysiological or clinical features which may differentiate the depressed phase of bipolar disorder from the depressed phase of unipolar depression. Any such demonstration of distinguishing features would be of considerable clinical value, particularly for first-onset depressive episodes or when no accurate history is available. More importantly, differing clinical presentations (or phenotypic expressions) might indicate differential biological determinants.

Whilst a number of biochemical and endocrine investigations have been undertaken, with some studies suggesting possible biological differences between these syndromes (e.g., Roy et al. 1985; Carroll 1994), there have been relatively few comparative studies of clinical features. In this chapter we examine for differences in clinical features – and particularly for differences in psychomotor disturbance – between bipolar and unipolar melancholic depressed patients, as psychomotor retardation has traditionally been considered to be more prevalent in bipolar depression (Goodwin and Jamison 1990).

In relation to clinical features, Leonhard (1979) emphasised both variability between episodes and the polymorphic nature of both the depressed and manic phases of bipolar disorder, with the term “polymorphic” used to describe his observation of “signs of lability toward the other pole.” Leonhard also believed that “partial states” (i.e., those with the absence of essential single symptoms, for example, “unproductive mania”) were characteristic of both phases of the bipolar form, in comparison to the “pure” presentations of unipolar melancholia or unipolar mania.