Austrian-born French psychologist who introduced the term dementia praecox (schizophrenia) to refer to a mental and emotional deterioration beginning at the time of puberty. The disorder was renamed schizophrenia in 1908 by the Swiss psychologist Eugen Bleuler.

A friend of the physiologist Claude Bernard and an admirer of Charles Darwin's work on evolution, Morel sought explanations for mental illness in heredity, although he later came to believe that external agents such as alcohol and drugs could also affect the course of mental deterioration. At the Mareville Asylum near Nancy, Fr., he studied the mentally retarded, searching their family histories and examining such influences as poverty and early physical illnesses. Morel saw mental deficiency as the end stage of a process of mental degeneration that included mental illness. He articulated his theory of mental illness in Traité des maladies mentales (1860; “A Treatise on Mental Illness”), in which he coined the term demence-precoce to refer to mental degeneration.