سن در مقاربت اول رابطه معکوسی با واکنش پذیری استرسی کورتیزول زنان دارد

Abstract The relationship between age at first sexual intercourse and salivary cortisol stress reactivity (to the Trier Social Stress Test; TSST; consisting of public speaking and mental arithmetic) was examined in healthy subjects (43 females and 36 males; ages 19–38). Women reporting earlier first intercourse had less intense cortisol increases in response to the stressor (a non-significant trend was observed for males), and faster recovery from the stressor. Results were not confounded by age, oral contraceptive use, depression scores, smoking status, or body mass index. It is concluded that earlier first intercourse is associated with less reactivity to and faster recovery from stress as indexed by this endocrine measure. Results are discussed in terms of genetic and psychological influences on first intercourse and implications for coping with interpersonal stress.

1. Introduction Age at first sexual (penile–vaginal) intercourse (AFI) has a significant genetic loading (Martin et al., 1977 and Dunne et al., 1997), and part of this mechanism appears to involve genes for dopamine D1 and D2 receptors (Miller et al., 1999). Women’s earlier AFI was predicted by better motor skills at age 5, a domineering and mature personality at age 9 (Udry et al., 1995), earlier menarche (Udry and Cliquet, 1982), adolescent perception of earlier autonomy and physical maturity, and lack of restraint (Rosenthal et al., 1999). AFI is associated with lifelong sexual benefits as well: women’s earlier AFI is associated with greater coital orgasmic capacity (Raboch and Bartak, 1983), and in one sample (of unknown representativeness) of 64-year-old men, the sexually functional were differentiated from the nonfunctional by earlier AFI (Vallery-Masson et al., 1981). In several studies, AFI was associated inversely with adult intercourse frequency (reviewed in Brody (1997). Both AFI (in some studies of women; Paul et al., 2000) and cortisol response to stress (Seeman, 1995) have been found to be related inversely to self-esteem. The domineering and autonomous features noted above to be associated with earlier AFI have a parallel in the finding that social dominance and internal locus of control were associated with lower cortisol reactions (Pruessner et al., 1997) to the Trier Social Stress Test (TSST). In addition to genetic influences and behavioral manifestations of dopaminergic tone influencing cortisol response to social stress, cortisol responses may influence dopamine function. In laboratory animals, treatment with cortisol (at levels simulating a prolonged stress response) impaired dopamine-dependent prefrontal cortical functions (Lyons et al., 2000). Similarly, chronic psychosocial stress reduced the density of dopamine transporters in the caudate nucleus and putamen, and also reduced serum testosterone and testicular weight (Isovich et al., 2000). One may conjecture that chronic cortisol elevations associated with greater stress response could also interfere (or have interfered) with the dopamine-related initiation of sexual behavior. There are several pathways by which younger AFI might reduce stress response: earlier AFI could be a marker of a genetic predisposition against stress response, earlier AFI could have interpersonal and intrapsychic consequences leading to less stress response, and/or earlier AFI could be a precursor of more frequent intercourse, which results in less stress response. For the current study, the relationship between AFI and cortisol response to psychological stress was examined in a sample of healthy adults. To investigate one possible mechanism for differences in cortisol response (modification of adrenal sensitivity), the cortisol response to ACTH stimulation was also examined.

Results The ANOVA using a sex-specific median split had a significant interaction of Time with median split AFI in females (F(6, 246) = 2.95, p = .048, Greenhouse–Geisser epsilon = .408; see Fig. 1), but not in males (F(6, 204) = 2.0, p = .12, Greenhouse–Geisser epsilon = .537). For the females, there was no significant baseline difference, but the AFI ≥ median group had a more intense cortisol reaction to the TSST than did the < median group (at time +20 min [t = 3.2; p<.01]; as well as a possible anticipation effect at time TSST +1 min [t = 2.9; p<.01]). It should be noted that the AFI below median group had a milder, but not a completely “blunted” cortisol reaction (levels did increase a statistically significant and meaningful 50%). A separate analysis excluding the virgins obtained very similar results. A separate analysis using the criterion of age at first intercourse before age 17 obtained a stronger effect for females (F(6, 246) = 5.4, p < .003, Greenhouse–Geisser epsilon = .434; there were also significant differences at more time points), but not males. Salivary cortisol (nmol/l) response to psychological stress (TSST) in males and ... Fig. 1. Salivary cortisol (nmol/l) response to psychological stress (TSST) in males and females by sex-specific median split ages at first intercourse (AFI; <19 vs. ≥19 or never male, <18 vs. ≥18 or never female). Figure options In stepwise multiple regression analysis, the baseline-adjusted area under the cortisol curve for females was predicted by AFI (r = .41; F = 8.26, p = .006). No other variables entered the equation (the closest were smoking status: t = 1.9, p = .06, and oral contraceptive use: t = 1.6, p = .11; all others were t < 0.8, p > .45). In the forced entry model, female area under the curve was predicted by AFI (t = 2.1, p = .048; all other predictors were t < 1.4 and p >.19), with the overall model only marginally significant (p = .08) due to degradation of degrees of freedom. No variables predicted area under the curve for males in either analysis. As depicted in Fig. 2, there were no significant effects of AFI (as indexed by the median split) for either sex on the time course of plasma cortisol response to ACTH stimulation (both F < 0.6 and p > .5). Cortisol (μg/dl) response to 1 μg of ACTH (baseline, 45 min, 60 min) by ... Fig. 2. Cortisol (μg/dl) response to 1 μg of ACTH (baseline, 45 min, 60 min) by sex-specific median split ages at first intercourse (AFI; <19 vs. ≥19 or never male, <18 vs. ≥18 or never female) and sex