Why do we get the stress-related diseases we do? Why do some people have flare ups
of autoimmune disease, whereas others suffer from melancholic depression during a
stressful period in their life? In the present review possible explanations will be
given by using different levels of analysis. First, we explain in evolutionary terms
why different organisms adopt different behavioral strategies to cope with stress.
It has become clear that natural selection maintains a balance of different traits
preserving genes for high aggression (Hawks) and low aggression (Doves) within a population.
The existence of these personality types (Hawks-Doves) is widespread in the animal
kingdom, not only between males and females but also within the same gender across
species. Second, proximate (causal) explanations are given for the different stress
responses and how they work. Hawks and Doves differ in underlying physiology and these
differences are associated with their respective behavioral strategies; for example,
bold Hawks preferentially adopt the fight-flight response when establishing a new
territory or defending an existing territory, while cautious Doves show the freeze-hide
response to adapt to threats in their environment. Thus, adaptive processes that actively
maintain stability through change (allostasis) depend on the personality type and
the associated stress responses. Third, we describe how the expression of the various
stress responses can result in specific benefits to the organism. Fourth, we discuss
how the benefits of allostasis and the costs of adaptation (allostatic load) lead
to different trade-offs in health and disease, thereby reinforcing a Darwinian concept
of stress. Collectively, this provides some explanation of why individuals may differ
in their vulnerability to different stress-related diseases and how this relates to
the range of personality types, especially aggressive Hawks and non-aggressive Doves
in a population. A conceptual framework is presented showing that Hawks, due to inefficient
management of mediators of allostasis, are more likely to be violent, to develop impulse
control disorders, hypertension, cardiac arrhythmias, sudden death, atypical depression,
chronic fatigue states and inflammation. In contrast, Doves, due to the greater release
of mediators of allostasis (surplus), are more susceptible to anxiety disorders, metabolic
syndromes, melancholic depression, psychotic states and infection.