Clinical endophenotypes: Implications for genetic and clinical research

The last 100 years have witnessed an unprecedented attempt by Western medicine to combine codified diagnostic systems with empirically derived treatment to identify and palliate disorders of mood, thought, and communication. Today,most individuals suffering from afflictions of mood or thought can be reliably classified into categorical “disorders” or “diseases,” based on classification systems such as the Diagnostic and Statistical Manual for Mental Disorders (DSM) (1) or the International Classification of Diseases (ICD) (2). Yet, despite advances in illness classification and the wide variety of therapies available, persons suffering from severe mental illnesses (e.g., bipolar disorder and schizophrenia) continue to endure debilitating symptoms and experience occupational and social dysfunction accordingly (3,4). In arecent publication sponsored, in part, by the World Bank, several psychiatric disorders were listed as among the ten most disabling illnesses (5).