Karl Leonhard was born in 1904 and is customarily regarded as a follower of the Wernicke-Kleist school of thought (1). In 1936, he accepted a position as head of the department at the Frankfurt University Mental Hospital. He followed Karl Kleist (1879–1960) and worked closely with him until Kleist’s retirement in 1950 (2). Kleist had been a pupil of Karl Wernicke and had developed a complicated psychopathology based on Wernicke’s experience, gained mostly from the study of traumatic brain injuries. Although well-known for his work on aphasia, Wernicke (1848–1905) was a pioneer in biological psychiatry in the areas of both descriptive psychopathology and a comprehensive neuropathological framework (2).
Leonhard developed a highly differentiated classification system for the endogenous psychoses. He focused on refining Kleist’s clinical descriptions and turned to genetics in his quest for etiological hypotheses. Drawing on nearly 60 years of personally conducted long-term follow-up and family studies, Leonhard delineated sharply circumscribed subtypes based on signs that were easily observable, easily elicitable, or both (1).
Leonhard’s work, originally published only in German, was largely ignored in American psychiatry (2). After the translation of his monograph in 1979, however, he gained the attention of Washington University (St. Louis) and other diagnostically oriented psychiatry departments (3). While modern researchers can find obvious shortcomings in Leonhard’s nosology concerning methodology and etiology, his clinical descriptions are excellent. The Leonhard classification is complex, yet it foreshadowed modern classification of psychoses. Specifically, Leonhard promoted 1) affective psychoses with a unipolar-bipolar dichotomy, 2) schizophrenia with multiple subtypes and family studies, 3) periodic catatonia, and 4) cycloid psychoses (4).
His systems of description and classification remain valuable for investigators examining the psychopathology and other essential features of the psychoses. The Wernicke-Kleist-Leonhard Society met in Wurtzburg in 1989 for its first symposium and is still active today (3).