On the simple and the complex in psychiatry, with reference to DSM 5 and Research Domain Criteria.

The author reflects on the misleading effects of simple and the complex theories in psychiatry. He states that more than 3000 different forms of attention-deficit/hyperactivity disorder (ADHD) can be defined by combining the 18 items listed in the the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). To identify genetic and environmental risk factors which correlates with psychiatric disorders, endophenotype approach is used in many empirical studies.