The article proceeds as follows. In 2 and 3, I examine questions concerning the naturalness of depression and suicide. In Section 2, I critically examine the views of Thomas Szasz and Ian Hacking who offer different reasons for rejecting the existence of natural kinds in psychiatry. I subsequently propose a positive theoretical account of natural kinds in psychiatry that maintains that some mental disorders are natural kinds insofar as members of a kind share the same biological causal structure. More specifically, natural kinds in psychiatry (e.g., schizophrenia, bipolar disorder) are stable objects of classification whose characteristic signs are determined by networks of stable biological mechanisms.