Mendel is best remembered for the introduction of duboisine as a treatment for Parkinson's disease. Duboisine is an extract from the Australian plant Dubosia myoporoides. Mendel was an advocate concerning the unification of psychiatry and neurology as complementary disciplines. He also did important studies of epilepsy and progressive paralysis.
Among his medical writings is a textbook on psychiatry titled A Psychological Study of Insanity for Practitioners and Students, which has been translated into English.