Individual differences in defensive stress-responses: the potential relevance for psychopathology

Alterations in primary freeze and fight-or-flight reactions in animals have been associated with increased vulnerability to develop anxious or aggressive symptomatology. Despite the potential relevance of these primary defensive responses for human stress-coping, they are still largely unexplored in humans. The present paper reviews recent evidence suggesting that individual differences in primary defensive stress responses in humans are associated with individual differences in anxiety and aggression. In addition, we discuss (neuro)endocrine systems that may underlie increased freezing and flight behavior in anxiety and increased fight tendencies in aggression-related disorders. We conclude with a research agenda for the study of human defensive stress-responses as potential behavioral markers for stress-related disorders, including anxiety and aggression.