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Prenatal Stress and Homosexuality

Amanda Stevens

November 11, 2008

 

 

            Two topics of growing importance and interest in our society are stress and homosexuality. In today’s world, stress seems to be inevitable. We are constantly being bombarded with stimuli telling us to loose weight or buy a new car. We can be reached 24/7 via cell phone or blackberry, so nobody ever has a moment of peace. Homosexuality is a controversial subject that has become quite a hot topic in politics, and is slowly becoming more accepted, or tolerated, in society.

 

STRESS!

            Stress is not just an automatic feeling we get for no reason when we are overwhelmed. It is thought to be an adaptational process that evolved to help us cope with what lies ahead of us. Stress “is the process by which a person both perceives and responds to events that are judged to be challenging or threatening” (Straub 2007). In this process, the person must first evaluate the situation he or she is in. If the situation is found to be either threatening or challenging, then it will be evaluated as stressful, and the person must respond in some way which will relieve the stress, by removing, ignoring, changing, overcoming or coping with the stressor.

            When a situation has been evaluated as “stressful,” the body’s biological systems kick in, and we experience a biological response that is called “fight or flight.” The fight or flight response is controlled by two branches of our nervous system, the sympathetic and the parasympathetic nervous system. When a threat or challenge is perceived, the body’s sympathetic nervous system is switched on, raising the level of two hormones, epinephrine and norepinephrine. These hormones cause a series of biological changes, such as increase heart rate, dilation of nostrils and bronchial tubes, raises blood pressure, increases blood flow to brain and muscles, which gear up the body to either flee from the perceived danger, or stay and fight. Once the perceived danger or challenge is no longer a threat, the body’s parasympathetic nervous system kicks in, and returns all body systems back to normal levels of functioning. However, when the body suffers a long period of chronic stress, many of the body’s functions are thrown out of whack, resulting in a depletion of the body’s resources, weakening and possible failure of the immune system, the pituitary gland can not produce enough stress hormones, and other negative health effects.

 

Homosexuality

 

            For years now we have been researching possible causes of homosexuality, and there are a wide range of theories varying from it is a lifestyle choice, to it is a genetic trait, and everything in between. One theory that has been gaining attention in the field of sexual orientation research is that prenatal stress, stress suffered by the pregnant mother, is a possible cause of homosexuality in males.

            While everyday stressors, like losing your keys or waiting in line at the DMV, are most likely not severe enough to cause a change in the prenatal environment of a fetus, the research into the relationship between prenatal stress and male homosexuality, especially in our furry friends, the laboratory mice, has found a strong correlation between the two.

 

Which leads us to our question…

 

Does prenatal stress, caused by external stress experienced by the mother, cause homosexuality in humans???

 

 

                                   +

 =   ?

 

What started this theory?

 

         Early experiments led by G. Dörner, conducted on rats revealed that homosexual tendencies, sexual arousal by partners of the same sex, was exhibited by male rats who had been exposed to an androgen deficiency during perinatal sexual differentiation of the brain, even though normal to high levels of androgen were present in adult stages. If androgen deficiency is not induced, it can often be found in male rat fetuses and newborns of stressed mothers (Dörner 1983).

         These findings led Dörner to question whether extreme stress experienced by pregnant humans would also lead to homosexuality in their male offspring. So, he studied the frequency of homosexuality in males born in Germany before, during and after World War II. Out of 865 homosexual males studied, significantly more were of them were born between the critical period of the war (“between 1941 and 1947- with a maximum in 1944-1945”) than in the years before or after the “critical period” (Dörner 1983). These findings spurred a second study by Dörner, which yielded similar results. In this second study, Dörner used a sample of 100 bi- or homosexual men and 100 heterosexual men. In turn, each was asked about possible stressful life events that took place in his mother’s life during her pregnancy with him. The findings were as follows:

1.      “Out of 100 heterosexual males only 6 heterosexuals reported on moderate stressful events that have occurred in their prenatal life, while none of them described severe stressful events in prenatal life, even after consulting their parents.

2.      Out of 40 bisexual men 10 bisexuals (=25%) described moderate and 6 bisexuals (=15%) even severe stressful events that have occurred in prenatal life.

3.      Out of 60 homosexual men 20 homosexuals (=33.3%) reported on moderate and 21 homosexuals (=35%) even on severe stressful events that have occurred during their prenatal life. (Dörner 1983)”

       These findings indicate that there is a correlation between prenatal stress and bi- or homosexuality in males. Dörner acknowledges that errors can be attributed to a restrospective study, such as this one, and prospective studies should be conducted in the future to further supplement his findings.

 

         While the correlation seems like a good indicator of causation, there are many problems with this study. Dörner did not supply the method with which he chose his subjects, how he rated the “stressfulness” of their situations, and retrospective studies are entirely based upon memory, which can not be regarded as 100% fact.

 

 

                    

Oh, Rats! (Or mice…)

 

            Though Dörner’s experiments did not prove the theory, the effect of prenatal stress on the sexuality of offspring continued to be tested repeatedly through experiments with pregnant rats. In 1994, Ward et al. published findings to support Dörner’s original studies on the effects of prenatal stress on sexual behaviors in rats. The female rats were mated with males, and separated into several groups (only 2 of which will be discussed here, because the effect of alcohol was also being tested, but is not being discussed in this paper). The two groups in question received identical treatment, with the exception of the experimental group had stress induced. The apparatus used to induce stress on the pregnant females was a Plexiglas animal holder with two floodlights attached over the surface. Between days 14-21 of pregnancy, the female rats received the stress treatment three times per day, for 45 minutes per session. After birth, the male progeny were tested for displays of female and male copulatory patterns. The findings revealed that 73% of males with prenatal exposure to stress led to the development of female sexual behavior, but did not affect the ability of ejaculation. However, when presented with an estrous female, 54% of males still ejaculated, implying bisexual behavior. The results were attributed to the fact that stress “is known to block the testosterone surge that normally occurs on Days 18 and 19 of gestation in male fetuses. This surge has been linked to the normal development of sexually dimorphic behaviors” (Ward 1994). Stress causes a lack of testosterone that is needed to fully masculinize the male brain and lead to normal male copulatory behavior.

 

So, the evidence seems pretty solid, right?

 

But the plot thickens…

 

            While Dorner’s experiment in combination with the rat studies seems to make a pretty strong case, Dorner’s results have yet to be successfully repeated. J. Michael Bailey, et al., attempted a similar experiment. In the experiment, questionnaires were sent home to the mother’s of the subjects. The questionnaires asked the mother to assess their child’s childhood gender conformity behavior, the number of homosexual or bisexual siblings that the subject had, a life events questionnaire, which measured the stress experienced by the mother during her pregnancy, scales to measure stress proneness of the mother, and an assessment of the mother’s assessment of the subject’s gender conformity in the subject’s childhood personality. The questionnaires were completed by 83 mothers of male nonheterosexuals, 60 mothers of male heterosexuals, 19 mothers of female nonheterosexuals, and 53 mothers of female heterosexuals. The study found no statistically significant difference in the amount of stress suffered by mothers of nonheterosexual males and mothers of heterosexual males, contrasting sharply with Dorner’s results. However, it was found that mothers who rated their sons as more effeminate “were found to be more stress prone than mothers of gender-conforming boys.

             A possible explanation for the inconsistent results is the level of stress that was suffered by the mothers. The stress level experienced in a World War II Germany, in Dorner’s first study, is much different from that experienced by North Americans in the late 1980’s. The stressors listed in Dorner’s second study included husband at war, undesired pregnancy, death of husband or family member, maltreatment, rape and other experiences. The most common stressful experience listed by mothers in Bailey’s study was “moved residence,” while others included “change in pattern of work or job,” and the most stressful experience was “death of a friend.”

 

Ethical barriers

 

            Scientists can not ethically, or legally, induce the levels of stress equal to that put on the mice, on pregnant women in an attempt to discover whether or not causality exists between prenatal stress and homosexual male progeny. So, if we can not induce the stress on humans to experimentally test the impact, scientists either have to wait for another catastrophic event, like a world war, to occur, then wait for children to be born, and take into account all other factors and confounding variables that were not controlled for because it was not an experiment or find some other way.

 

Other problems

 

            While the scientific knowledge of the stages of a fetus’ development is vast, the exact stages and timing of neurological development is very difficult to detect, thus, even if it were ethical, testing on pregnant women would be very difficult because stress would have to be induced before the neurological development of the fetus, especially sexual hot spots, like the hypothalamus and the Sexually Dimorphic Nucleus.

 

Questions to ask in the future

 

            Wouldn’t there be a higher population of gay men in countries stricken with war, extreme poverty, famine or other daily, life threatening stressors?

            What are other possible causes of homosexuality?

 

The jury is still out…

 

            While the findings in the rat studies, that maternal stress during gestation causes differential sexual behavior in their male offspring, are seemingly indisputable, the findings can not yet be applied as fact for humans. Much more research needs to be done looking at the correlation and causation of prenatal stress and homosexuality, as well as other possible causes, such as genetics and other prenatal environmental factors.

 

 

Works Cited

 

Bailey, J. M., L. Willerman, et al. (1991). "A test of the maternal stress theory of human male homosexuality." Archives of Sexual Behavior 20(3): 277-93.

 

Dörner, G., T. Geier, et al. (1980). "Prenatal stress as possible aetiogenetic factor of homosexuality in human males." Endokrinologie 75(3): 365-8.

 

Dörner, G., B. Schenk, et al. (1983). "Stressful events in prenatal life of bi- and homosexual men." Experimental and Clinical Endocrinology 81(83-87).

 

Ellis, L., M. A. Ames, et al. (1988). "Sexual orientation of human offspring may be altered by severe maternal stress during pregnancy." Journal of Sex Research 25: 152-157.

 

Hines, M., K. J. Johnston, et al. (2002). "Prenatal stress and gender role behavior in girls and boys: a longitudinal, population study." Hormones and Behavior 42(2): 126-34.

 

Straub, Richard O. (2007). Health Psychology: A Biopsychosocial Approach. New York: Worth Publishers.

 

Ward, I. L. (1972). "Prenatal stress feminizes and demasculinizes the behavior of males." Science 175(17): 82-4.

 

Ward, I. L., O. B. Ward, et al. (1994). "Male and female sexual behavior potential of male rats prenatally exposed to the influence of alcohol, stress, or both factors." Behavioral Neuroscience 108(6): 1188-95.

 

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