Commentary: biological findings in PTSD -- too much or too little?

Summarizing the contributions in this section of the book, this chapter addresses questions regarding the complex etiology of PTSD, and the relative strength of discernable biological indicators of the disorder. It outlines two major approaches to exploring the biology of the disorder and discusses the reason for the many non-replications of findings. It defines the constructs of multicausality, equifinality, and multifinality, and evaluates their main implication for studies of PTSD, namely that no biological signal can be properly appraised without taking into account its context. Such context, in PTSD, includes both concurring biological systems and regulatory mechanisms, and environmental-psychosocial input. Studies of gene expression of PTSD exemplify one way of studying the context of putative biological signals. The role of biological alterations as templates for responding to psychosocial challenges is discussed.