Affective and schizophrenic disorders are not monolithic concepts. The idea of groups of disorders has proved to be useful. Today the concept of a spectrum of affective disorders and a spectrum of psychotic disorders is based on clinical and research findings. It has also been proposed that a kind of continuity exists between the two spectra. There are clinical bridges joining them, or perhaps some nosologic islands filling the gaps in-between. Possibly what is “in-between” represents a cross of the underlying dimensions of the two “voluminous” spectra, or a superposition of some of the contributory factors of one or that of the other.
Psyche is like Physis – Nature. She does not take any leaps, even when she is ill. Emil Kraepelin himself realized the indistinct boundaries of the dichotomy of the manic-depressive and schizophrenic psychoses he had proposed at the turn of the nineteenth century. He thought that it was only partially true. One can read it in his paper published in 1920: “Die Erscheinungsformen des Irreseins”, which means “The manifestation types of insanity”. Among other relevant observations, he noted:
No experienced psychiatrist will deny that there is an alarmingly large number of cases in which, despite the most careful observation, it seems impossible to arrive at a reliable diagnosis … We therefore will have to get used to the fact that the symptoms we have used so far are not sufficient to always reliably distinguish between manic-depressive insanity and schizophrenia, but that there are overlaps based on the origin of these symptoms from given preconditions.