Psychobiological allostasis: resistance, resilience and vulnerability.

The brain and body need to adapt constantly to changing social and physical environments. A key mechanism for this adaptation is the 'stress response', which is necessary and not negative in and of itself. The term 'stress', however, is ambiguous and has acquired negative connotations. We argue that the concept of allostasis can be used instead to describe the mechanisms employed to achieve stability of homeostatic systems through active intervention (adaptive plasticity). In the context of allostasis, resilience denotes the ability of an organism to respond to stressors in the environment by means of the appropriate engagement and efficient termination of allostatic responses. In this review, we discuss the neurobiological and organismal factors that modulate resilience, such as growth factors, chaperone molecules and circadian rhythms, and highlight its consequences for cognition and behavior.