This chapter frames problems that reflect the split between biological psychiatry and psychotherapy, and promotes a biopsychosocial model of etiology for most mental disorders. Findings with regard to genetics, neurotransmitters, and imaging methods are reviewed, and their limitations are highlighted. A similar critical review is applied to purely psychosocial interpretations of etiology with a focus on post-traumatic theories of mental disorders. The chapter emphasizes that constructs in science which have some applicability are often expanded into what can be called “concept creep.”