stress rarely occurs in isolation from other stresses or in a timely fashion so that it can be easily studied. One of the best characterized forms of psychosocial-stress-induced reproductive dysfunction comes from studies of women who present to infertility clinics with functional hypothalamic amenorrhea (FHA). By definition, FHA is a state of subfertility that is not associated with substantial undernutrition or exercise, does not involve lactation, and is not associated with any organic or structural causes for decreased fertility (Berga et al., 1989; Reame et al., 1985). Studies of women with FHA show that they experience more psychological stress than other women, although they do not experience more stressful life events but rather react more profoundly to the stressful events they do experience (Giles and Berga, 1993). They also show increased activation of physiological systems that respond to stress, including increased HPA axis activity (Berga et al., 1997). Treatment of these patients with cognitive behavioral therapy or with drugs that reduce the activity of some central neural systems activated by stress can restore fertility, although not in all cases (Berga et al., 1991, 1997).
Although the majority of studies examining the effects of psychosocial stress on reproduction have documented stress-induced suppression of reproductive function, there are a handful of human studies which have reported that girls who have grown up under conditions of family stress, such as an absent father in a home, with family conflict, a girl whose parents have divorced, enter puberty at a significantly earlier age (Belsky et al., 1991; Moffitt et al., 1993; Wierson et al., 1993). However, the mechanisms by which such stress exposure would advance the onset of puberty have not been established. Moreover, there is the possibility that early stress exposure does not cause advancement of puberty but rather that the likelihood of early puberty and exposure to early life family stresses may simply be correlated because they are both influenced by a common factor(s). For example, one of the factors governing the age of menarche in a girl is her mother’s age at menarche (Graber et al., 1995). Thus, it is possible that mothers who experienced early menarche are more likely to have family conflict or divorce when their children are young as well as to have daughters who will have early menarche themselves.
A more detailed understanding of how psychosocial stress can impact reproduction comes from animal studies, with investigations in nonhuman primates having particular relevance to understanding this human condition. Nonhuman primates live in complex social groups and have higher cortical brain areas similar to humans. Moreover, the anatomical and functional organization of their reproductive axes is very similar to humans. A number of studies have shown that acute stresses, such as placing monkeys in restraint chairs (Norman and Smith, 1992), receiving aggressive attacks from other monkeys (Rose et al., 1972), and pairing with unfamiliar part-