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Adaptation to Stress 107

Oxytocin and vasopressin are two neuropeptides that have been strongly
implicated in the regulation of social attachment and the promotion of posi-
tive social interactions (Bartz & Hollander, 2006) as well as in the mediation

of the anxiolytic effects of social support . Diff erential oxytocin and vasopres-

sin receptor expression patterns in specific areas of the brain (ventral palli-

dum and medial amygdala) have been shown to influence the type and the
duration of social attachments formed by voles. For example, montane voles
typically avoid social contact except while mating; they have lower levels of
oxytocin receptors in the nucleus accumbens compared with prairie voles,
which are highly social and typically monogamous (Insel & Shapiro, 1992).
Oxytocin is critical for learning social cues and has been shown to enhance
maternal care in rats (Francis, Champagne & Meaney, 2000). Oxytocin also

exerts anxiolytic effects that are associated with attenuated secretion of cor-
ticosterone in lactating rodents (Neumann, Torner & Wigger, 2000). One
recent study showed that oxytocin served to increase the calming eff ects of
social support among healthy men undergoing the Trier Social Stress Test
(Heinrichs, Baumgartner, Kirschbaum & Ehlert, 2003).
Preclinical studies suggest that social isolation is associated with elevated
heart rate and blood pressure, hypercortisolemia, and atherosclerosis
(Rozanski, Blumenthal & Kaplan, 1999). Results from human studies are
consistent in that low social support is associated with increased blood
pressure (Uchino, Cacioppo & Kiecolt-Glaser, 1996) and exaggerated car-
diovascular and neuroendocrine responses to laboratory stressors (Steptoe,
Owen, Kunz-Ebrecht & Brydon, 2004). There is also a vast animal literature

to suggest that social support plays a critical role in normal development
and responses to early life stressors (for a thorough review, see Kaufman,

Plotsky, Nemeroff & Charney, 2000).
In short, the available literature suggests that neurobiological factors play
a role in forming social attachments and in mediating the benefi cial behav-
ioral and neuroendocrine effects of social support. Th ese fi ndings suggest

that it may be possible to intervene and enhance resilience in at-risk individ-
uals by providing them with nurturing environments and social support.

Possible Interventions
Th e findings and relationships reviewed in this chapter have implications

for the prevention and reversal of stress-induced alterations in neurobiologi-
cal systems and associated behavior and psychiatric symptoms. For example,
it may be possible to enhance stress resilience by providing social support,

improving aerobic fitness, learning cognitive strategies that promote opti-
mism, and incorporating training principles that serve to “inoculate” against
future stress or trauma. In the context of military readiness, these objectives
might take the form of refined or additional group training and education

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