Biology Reference
In-Depth Information
syndrome
[41,42]
. However, the prevalence of the metabolic syndrome varies consid-
erably between studies, mainly due to different definitions used, but also due to other
factors such as differences between gender and ethnic groups
[42,43]
.
Thus, having a “thrifty gene” favouring survival in primitive life may in our mod-
ern society “back-fire” as e.g. the effects of glucocortiocoids are often combined
with high caloric intake and physical inactivity
[34]
. Individuals frequently respond-
ing with defeat reactions and the associated activation of the HPA axis may thus be
more vulnerable to metabolic diseases and also to immunological disturbances.
Post-traumatic stress disorder (PTSD), which may be considered to be a deci-
sive consequence of prolonged defeat reaction in man, is frequently comorbid with
the metabolic syndrome, and particularly if the patients also suffer from depression
[44]
. Furthermore, several studies indicate that people with severe PTSD show a dys-
regulation in HPA-axis function. Briefly, glucocorticoid levels are usually consider-
ably lower in PTSD patients than in healthy controls, believed to be a result from an
enhanced negative feedback by glucocorticoids, which is secondary to an increased
sensitivity of glucocorticoid receptors in target tissues
[45]
.
One distinct difference between the defeat and defence reactions, seen in e.g. ani-
mal experiments is that gonadotrophins and testosterone as well as growth hormone are
suppressed in defeat reactions, while they are increased in defence reactions
[46]
. In
humans, the pictures are often far more complex and data concerning the effects on sex
steroids are not consistent, which may reflect that in complex modern life the defence
and defeat reactions can frequently shift from the one-to-the-other as daily life situa-
tions change from day to day. However, animal experiments are commonly so designed
as to promote “the-one” or “the-other” in an “either-or” fashion to simplify analyses.
11.5 The Complexity of Defence and Defeat
Reactions in Modern Man
Translating the defence and defeat reactions to humans and life challenges in today's
society is far from easy, as in reality present-day man can be faced with many situa-
tions even during the same hour, causing shifts between defeat or defence reactions.
While the so-called freezing reaction or playing dead reaction, as explored in ani-
mals
[3]
(the equivalents of vigilance response and emotional fainting in man) usually
are very brief (seconds or minutes), defence reactions, and particularly defeat reac-
tions, can in modern life be quite sustained and frequently induced, though usually in
mild forms. Even though their physiological expressions differ considerably, defence
and defeat reactions are in man's situation often “blended” in various constellations,
depending on situation, earlier experience, genetics, etc. For such reasons the net out-
come in man can be complex, indeed, and quite intricate to analyse, and this was in
fact also the case in Henry's mice colonies.
In today's modern society, millions-of-bits of information reach the brain each
minute, though, thanks to blissful inhibitory mechanisms at subcortical and corti-
cal levels, consciousness is not overwhelmed by such bombardments. In fact, recent
developments in neuroscience suggest that stimulating the brain through training of
