问答题Passage 2　　Many scientists have wondered whether there is some quirk in the way depression is inherited, such as a depressed parent or grandparent is more likely to pass on a predisposition for the disorder to female than to male descendants. Based on

Passage 2　　Many scientists have wondered whether there is some quirk in the way depression is inherited, such as a depressed parent or grandparent is more likely to pass on a predisposition for the disorder to female than to male descendants. Based on studies that trace family histories of depression, the answer to that question appears to be no. (1)______　　Simply tracing family histories, though, without considering environmental influences, might not offer a complete picture of how depression is inherited.　　Indeed, Kenneth S. Kendler and his colleagues at the Medical College of Virginia found in a study of 2060 female twins that genetics might contribute to how women respond to environmental pressures. The researchers examined twins with and without a family history of depression; some twins in both groups had recently undergone a trauma, such as the death of a loved one or a divorce. The investigators found that among the women who did not have a family history of depression, stressful events raised their risk for depression by only 6 percent. (2)______.　　A similar study has not been done in men, leaving open the question of whether environmental stress and genetic risk for depression interact similarly in both sexes. But research is being done, to determine whether men and women generally experience similar amounts and types of stress. Studies of key hormones hint that they do not. Hormones are not new to depression researchers. Many have wondered whether the gonadal steroids estrogen and progesterone--whose cyclic fluctuations in women regulate menstruation--might put women at a greater risk for depression. There are at least two ways in which they might do so.　　First, because of differences between theX and Y chromosomes, male and female brains are exposed to different hormonal milieus. (3)______.　　Indeed, animal experiments show that early hormonal influences have marked behavioral consequences later on, although the phenomenon is of course difficult to study in humans.　　Second, the fact that postpuberal men and women have different levels of circulating gonad steroids might somehow pull women at higher risk for depression. Research shows girls become more susceptible to depression than boys only after puberty, when they begin menstruating and experience hormonal fluxes. (4)______.　　For example, Peter J. Schmidt and David R. Rubinow of the National Institute of Mental Health recently reported that manipulations of estrogen and progesterone did not affect mood, except in women who suffer from severe premenstrual mood changes.　　It now appears, however, that estrogen might set the stage for depression indirectly by priming the body's stress response. During stressful times, the adrenal glands--which sit on top of the kidneys and are controlled by the pituitary gland in the brain--secrete higher levels of a hormone called cortical, which increases the activity of the body's metabolic and immune systems, among others: (5)______.　　Evidence is emerging that estrogen might not only increase cortical secretion but also decrease mortise’s ability to shut down its own secretion. The result might be a stress response that is not only more pronounced but also longer-lasting in women than in men.[A] But the same risk rose almost 14 percent among the women who did have a family history of depression. In other words, these women had seemingly inherited the propensity to become depressed in the wake of crises.[B] To figure out why depression is more common among women, scientists have to study how genetics and environment divide the sexes and how the two conspire to produce the symptoms we describe as depression.[C] In the normal course of events, stress increases cortical secretion, but these elevated levels have a negative feedback effect on the pituitary, so that cortical levels gradually return to normal;[D] Despite their importance, estrogen and cortical are not the only hormones involved in female depression, medium stress is not the only environmental influence that might hold more sway over women than men.[E] These hormonal differences may affect brain development so that men and women have different vulnerabilities and different physiological reactions to environmental stresses later in life.[F] Even so, scientists have never been able to establish a direct relation between emotional states and levels of estrogen and progesterone in the blood of women.[G] Women and men with similar heritage seem equally likely to develop disorder.