Introduction

Hardly any studies on schizoaffective mixed states exists. However, an exception is the Cologne study carried out by Marneros et al. in the 1980s and 1990s (Marneros et al., 1991). The rarity of research on schizoaffective mixed states is, on the one hand, a paradox, but on the other hand, an understandable phenomenon. Why a paradox? There are two reasons: first, while schizoaffective disorders are well established as diagnostic categories in both Tenth Revision of the International Classification of Diseases (ICD-10: World Health Organization, 1991) and Diagnostic and Statistical Manual of Mental Disorders (DSM-IV: American Psychiatric Association, 1994), it has also been determined that schizoaffective disorders have to be divided according to their mood component into unipolar and bipolar types, a fact that implicates the occurrence of schizoaffective mixed states (American Psychiatric Association, 1994; Marneros et al., 1989a–c; 1990a, 1990b; 1991; Marneros and Angst, 2000). Second, both diagnostic systems, ICD-10 and DSM-IV, define a schizoaffective mixed episode, as shown in Tables 8.1 and 8.2. Therefore, it is to be expected that clinicians and researchers applying either ICD-10 or DSM-IV criteria diagnose schizoaffective mixed episode. But neither clinical nor practical experience, as well as a study of the literature, supports such an assumption.

Then, why do these obvious deficits seem understandable? Mainly due to two reasons: first, the definition of schizoaffective disorders is – in spite of their long history and clinical reality – still diffuse and uncertain.