网范文：“The Functions of Postpartum Depression” 探讨表明,现在的父母不会主动投资后代,如果投资成本大于收益还会减少孩子的数量，英语论文范文，或不需要孩子。缺乏父亲的或社会的支持将增加成本,而婴儿的健康问题也是一大问题。在这篇医学范文中，许多探讨关于产后抑郁症的相关性，产后抑郁症可能是一个适应过程,母亲痛苦促使他们减少或消除投资。产后抑郁症也似乎是一个很好的缘由。
母亲产后抑郁症通常有伤害自己孩子的想法,对他们表现出更少的积极情绪,对婴儿减少响应和敏感信号，尽管大多数探讨人员认为产后抑郁症是一个心理障碍。产后抑郁症是一个过程,发生在产后一个月。下面的范文进行详述。
Abstract
Evolutionary approaches to parental care suggest that parents will not automatically invest in all offspring, and should reduce or eliminate investment in their children if the costs outweigh the benefits. Lack of paternal or social support will increase the costs born by mothers, whereas infant health problems will reduce the evolutionary benefits to be gained. Numerous studies support the correlation between postpartum depression (PPD) and lack of social support or indicators of possible infant health and development problems. PPD may be an adaptation that informs mothers that they are suffering or have suffered a fitness cost, that motivates them to reduce or eliminate investment in offspring under certain circumstances, and that may help them negotiate greater levels of investment from others. PPD also appears to be a good model for depression in general.
Keywords: postpartum depression, parental investment, life history theory, evolutionary psychology, reproduction, mental health
Introduction
Mothers with postpartum depression (PPD) commonly have thoughts of harming their children, exhibit fewer positive emotions and more negative emotions towards them, are less responsive and less sensitive to infant cues, less emotionally available, have a less successful maternal role attainment, and have infants that are less securely attached (Beck, 1995; Beck, 1996b; Cohn, Campbell, Matias & Hopkins, 1990; Cohn, Campbell & Ross, 1991; Field & et al., 1985; Fowles, 1996; Hoffman & Drotar, 1991; Jennings, Ross, Popper & Elmore, in press; Murray, 1991; Murray & Cooper, 1996).
Although most researchers view PPD as a disorder, evolutionary theorists frequently have argued that there are circumstances when it would in the mother’s fitness interest to reduce or eliminate her investment in her offspring, for example, when there is insufficient social support to raise the infant, or when the infant has low viability (Clutton-Brock, 1991; Daly & Wilson, 1984; Daly & Wilson, 1988; Hrdy, 1979; Hrdy, 1992; Trivers, 1974). PPD is a depressive episode with onset occurring one month postpartum (APA, 1994). 1 Depressive episodes are characterized by a number of symptoms including depressed or sad affect, marked loss of interest in virtually all activities, significant weight loss or gain, insomnia or hypersomnia, psychomotor agitation or retardation, fatigue or loss of energy, feelings of worthlessness or guilt, diminished ability to think or concentrate, and recurrent thoughts of death (APA, 1994). A diagnosis of a DSM IV major depressive episode requires that five of these symptoms be present during a two-week period, and that at least one of the symptoms is either depressed or sad mood, or a markedly diminished interest or pleasure in all or almost all activities.
Three correlates of PPD are consistently found by researchers: marriage problems and lack of social support, particularly the father’s (table 1), infant problems, including pregnancy and delivery problems (table 2), and a prior history of depression or other emotional problems (Atkinson & Rickel, 1984; Cutrona & Troutman, 1986; Gotlib et al., 1991; Graff, Dyck & Schallow, 1991; Logsdon, McBride & Birkimer, 1994; O’Hara et al., 1984; O’Hara, Rehm & Campbell, 1983; Whiffen, 1988; Whiffen & Gotlib, 1993). This will propose three related adaptive functions for PPD that are consistent with the expectations of evolutionary theorists and the first two correlates noted above. First, negative affect—i.e., sad or depressed mood—should be associated with social circumstances that were reproductively costly in ancestral environments (e.g., lack of social support or infant problems). This “psychological pain” hypothesis (Alexander, 1986; Nesse, 1991; Nesse & Williams, 1995; Thornhill & Thornhill, 1990; Thornhill & Thornhill, 1989; Tooby & Cosmides, 1990) is strongly supported by existing evidence. Second, mothers will take actions to reduce their levels of psychological pain, thereby reducing their reproductive costs. This hypothesis is also well supported by existing evidence.
The third hypothesis applies to major rather than minor PPD. A minor form of PPD involving fewer and less severe symptoms is sometimes distinguished from PPD involving a major depressive episode. 2 Minor PPD is consistent with the psychological pain hypothesis and the two proposed functions described earlier. Symptoms of major PPD not well accounted for by the psychological pain hypothesis—e.g., marked loss of interest in virtually all activities, psychomotor retardation, significant weight loss, diminished ability to think or concentrate, and recurrent thoughts of death—may enable the mother to negotiate greater levels of social support, the third functional hypothesis. In the same way that a valuable employee may attempt to negotiate a larger salary by threatening to quit, mothers receiving insufficient social support may attempt to negotiate larger levels of support by threatening to defect from (i.e., quit) the childrearing endeavor. This hypothesis cannot be adequately tested with the data that are currently available and it is justified on purely theoretical grounds; as such, it is quite speculative.
Because each of these hypotheses involves either an aspect of a mother’s decision to invest in or defect from childrearing, or her attempt to negotiate larger levels of support by threatening to defect from childrearing, I will refer to them collectively as the defection hypothesis for PPD. The defection hypothesis, its theoretical foundations, and supporting data will be presented in detail in the following sections. These data are not sufficient to prove the defection hypothesis, however. Other interpretations of the data are possible, and I consider it well beyond the scope of the to analyze these other interpretations (there is no consensus on the correct theoretical approach to PPD; see Affonso (1984), Cutrona (1982), and Hopkins (1984) for brief reviews of psychodynamic, personality, cognitive-behavioral, and biophysical theories of PPD. See Cramer (1993), Collins et al. (1993), Cutrona (1983), Cutrona and Troutman (1986), Gotlib et al. (1991), O’Hara et al. (1982), and O’Hara et al. (1984) for experimental tests of particular theories of PPD).
Parental investment theory
The close association of PPD with child bearing and rearing suggests that the application of parental investment (PI) theory may be quite fruitful (see, e.g., Clutton-Brock 1991). PI theory, an aspect of life-history theory, provides the evolutionary framework for nearly 20 years of research into parental investment in offspring for both humans (e.g., Betzig, Borgerhoff Mulder & Turke, 1988; Blurton Jones, 1989; Chisholm, 1993; Dickemann, 1979; Dickemann, 1981; Draper & Harpending, 1982; Hagen, 1996; Hagen, 1998c; Hagen, submitted; Haig, 1993; Hames, 1996; Hartung, 1982; Hartung, 1985; Hill & Kaplan, 1988; Hrdy, 1992; Lampert & Friedman, 1992; Voland, 1984) and other species(the literature is huge; for recent syntheses see Clutton-Brock (1991), Roff (1992) and Stearns 1992). Both PI theory and life-history theory (of which PI theory is a part) form the basis of this functional analysis of PPD.
To briefly review, life-history theory posits that in order to have left descendants, the ancestors of any species must have solved the problems of survival, growth, development on the one hand, and reproduction on the other. Because each of these problems is characterized by unique difficulties, and because time, energy, and resources are finite, organisms must optimally allocate these commodities between somatic effort (growth, development, and maintenance of the organism), and reproductive effort (producing offspring who themselves survive to reproductive age). Reproductive effort, in turn, should be optimally allocated between mating effort (locating and acquiring a mate), and parenting effort (e.g., gestation and raising of offspring)—what I have here termed parental investment in order to be consistent with existing literature (see Clutton-Brock 1991, p. 8, for a discussion of terminology).
PI theory focuses on those aspects of an organism’s life-history that are specifically involved with producing and raising offspring. Life history theorists assume that the physiological and behavioral characteristics of organisms represent an approximate solution to the problem of optimizing the allocation of time, energy, and resources between somatic, mating, and parenting effort, with the particular solution depending on the organism’s environmental niche as well as its evolutionary history. In general, effort allocated to reproduction will decrease an organism’s ability to survive, grow, and develop, whereas, conversely, effort allocated to survival, growth, and development will decrease reproduction. Similarly, effort allocated to finding a mate will decrease an organism’s ability to invest in offspring, whereas effort invested in offspring will reduce an organism’s ability to acquire a mate. If parental investment can only occur at the expense of somatic or mating effort, then parents need to decide, based on current circumstances, whether it is more advantageous to invest finite resources in offspring, mates, or themselves. Investment in new offspring should not be automatic.
A number of straightforward predictions follow from PI theory, two of which will be the focus of this . First, when offspring require significant investment from mothers, mothers should assess offspring viability (e.g., health) before providing the investment. Second, when offspring require significant investment from both fathers and mothers in order to survive to reproductive age, mothers should assess the availability of father investment before investing themselves. There is a correspondence between these two predictions of PI theory, and two widely replicated correlates of postpartum depression, namely the mother’s perception of lack of support from the father, and “infant problems,” including pregnancy and delivery problems (tables 1 and 2). While PI theory makes it clear why a mother who has an infant with problems or who is receiving insufficient social support will neglect, abandon, or kill her offspring, it does not make clear why these circumstances lead a mother to experience depression.
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