So, was Kraepelin right? An attempt to clarify the relationship between schizophrenia and bipolar disorder

Abstract

Biological view of the development of mental disorders was described back in the days of Hippocrates in his humoral theory considering the brain as a place of origin of all emotions and therefore rejecting the earlier theories suggesting that psychic phenomena resulted from divine intervention. Later his ideas transformed to produce, inter alia, the Kraepelin’s allegation. Kraepelin described mental disorder as a “natural biological process” and suggested to divide mental disorders into two large groups, dementia praecox and la folie circulaire, based on this allegation. Differentiation was based on intellectual impairment that was more severe in patients with schizophrenia than in patients with bipolar disorder. Current research has revealed considerable clinical and genetic similarity of two disorders. However, in contrast to schizophrenia, the data of patients with bipolar disorder indicate no intellectual impairment. Furthermore, the risk of bipolar disorder is associated with higher premorbid IQ. Can we suppose that the genes that determine such cognitive differences are just genes and their mutations that determine lower IQ in the general population, but not the disease-associated genes? High efficacy of antipsychotics against both disorders is the other common phenomenon revealed in modern times. Modern antipsychotics that will be discussed in this paper show higher efficacy and safety.

Keywords

• schizophrenia
• bipolar disorder
• cognition
• antipsychotics
• lurasidone