The capacity of animals to make allostatic adjustments through
change is necessary for survival. If they persist too long, the excess
cortisol can be damaging to the biological pathways influencing
brain function and physical and mental health.
In studies of stress and development in rats, investigators have
concluded that mothers’ care during infancy programs stress re-
sponses in their offspring by modifying the neural systems in the
LHPA axis. The findings from research in animals indicate that early
rearing conditions can permanently alter the set point for the control
of the LHPA system. This influences the expression of endocrine and
biological responses to stress throughout life.
This work has provided evidence about how early life events can
affect the function of the LHPA system and subsequent behavioral
and mood disorders, as well as atherosclerosis and arterial thrombosis
in animals. In their work, these investigators and others have con-
cluded that conditions in early life can permanently alter gene ex-
pression (the epigenetic effect).
The investigators have found that adverse maternal behavior can
lead to poor protein synthesis from DNA because of epigenetic effects
on the gene promoter functions. Since methylation (an epigenetic
pathway) of gene structures is difficult to reverse, this is a possible
mechanism for the long-term environmental effects of maternal in-
teraction with newborns on gene expression that can last throughout
life.
The production of cortisol is important in how individuals cope
with the daily demands of what they do. Overproduction of cortisol
can influence behavior and health, such as antisocial behavior, de-
pression, type II diabetes, cardiovascular diseases, memory, the im-
mune system, and risk of drug and alcohol addiction. Underproduc-
tion is associated with chronic fatigue syndrome, fibromyalgia,
autoimmune disorders, rheumatoid arthritis, allergy, and asthma.
Immune System
Another biological pathway that is influenced by the brain and the
LHPA pathway is the immune system. In her recent book, Sternberg
(2000) has outlined this pathway as follows—
Scientific Underpinnings of the Importance of ECD in a Global World 53