摘要：Objectives . We examined within-person associations between changes in family income and women’s depressive symptoms during the first 3 years after childbirth. Methods . Data were analyzed for 1351 women (mean baseline age = 28.13 years) who participated in the National Institute of Child Health and Human Development Study of Early Child Care. Nineteen percent of these women belonged to an ethnic minority, and 35% were poor at some time during the study. Results . Changes in income and poverty status were significantly associated with changes in depressive symptoms. Effects were greatest for chronically poor women and for women who perceived fewer costs associated with their employment. Conclusions . Given that women head most poor households in the United States, our findings indicate that reductions in poverty would have mental health benefits for women and families. Researchers interested in links between poverty and depression have begun using longitudinal data to account for volatility in family income. 1– 4 For example, it has been demonstrated that adults who are chronically poor are at greater risk for developing depression later in life than those who are transiently poor, when researchers control for current psychological functioning. 4 Because longitudinal studies have generally relied on between-person comparisons (e.g., rates of depression for chronically poor vs transiently poor populations), it remains unclear whether economic resource changes are associated with depressive symptom changes within individuals. If a person’s income rises, then do depressive symptoms diminish? Conversely, if income falls, then do depressive symptoms increase? Longitudinal analyses of within-person associations between income and depressive symptoms would answer these questions by estimating whether individuals’ income and depressive symptoms covary over time. In our study, within-person associations between changes in family income and changes in women’s depressive symptoms were examined periodically from 1 to 36 months after giving birth. A large body of literature has documented an increased risk of depression among women compared with men. 5 The postpartum period is a time of heightened vulnerability, in part because of hormonal changes that increase women’s psychological reactivity to high-stress conditions. 6, 7 In fact, approximately 10% of postpartum women experience clinical levels of depressive symptoms within the first few weeks after delivery, with the majority of these episodes lasting 6 months or less. 8 However, postpartum depression appears similar to depressive disorders occurring at other times in life with regard to both symptoms and precursors. 9 In general, depressive episodes may be transient, lasting a period of days, or chronic, lasting years. 7, 10 Life stressors such as financial strain and marital discord, as well as previous depressive episodes, are associated with an increased risk for depression, regardless of timing. 10 Yet the public health relevance of women’s depression during the first 3 years after childbirth is exceptional, primarily because maternal depression during infancy and early childhood has been well documented as a risk factor for children’s social-emotional development. 11– 13 Not surprisingly, women living in lowincome families are more likely than other women to be exposed to high-stress living conditions such as overcrowding, noise, and violent communities. 14 Thus, we predicted that changes in family income would be associated with changes in women’s depressive symptoms throughout the first 3 years after childbirth, such that increases in income would be linked with decreases in depressive symptoms. We also predicted that changes in poverty status would be associated with changes in depressive symptoms, such that moving out of poverty would be associated with decreases in depressive symptoms, above and beyond the effects of the corresponding income changes. Although reciprocal causation between income and depressive symptoms is possible, examining the role of employment offers the opportunity to test the direction of effect. Employment changes are, in fact, the most common reason for income gains and losses among poor families. 15 If income directly influences depression, then changes in hours of employment should be indirectly related to symptom changes. That is, associations between employment and depression should be due to income gains or losses resulting from work changes. However, if depression influences income, then events that affect earnings, such as hours of employment, should mediate the link. We examined 2 pathways linking changes in hours of employment, income, and depressive symptoms: (1) changes in hours of employment → changes in income → changes in depressive symptoms, and (2) changes in depressive symptoms → changes in hours of employment → changes in income. We predicted that our results would be consistent with the first pathway. Thus, we expected our results to be more consistent with social causation theories in which economic status is hypothesized to causally influence mental health rather than health selection theories in which mental health is hypothesized to causally influence economic status. 16– 17 Interactions between income changes and characteristics of women, their children, and their families were also examined to determine whether the association between changes in income and depressive symptoms varied across women. We expected the association between income and depressive symptoms to be larger for poor women than for nonpoor women, primarily because income gains and losses would have greater relative impacts on the economic resources of poor families (e.g., a $10 000 increase in income would be a 100% gain for families earning $10 000 per year and a 20% gain for families earning $50 000 per year). 18 We also expected the association to be larger for women who believed that the costs (i.e., detrimental effects) of maternal employment were low for their children compared with women who believed these costs were high. That is, we predicted that the positive psychological impact of income gains and the negative psychological impact of income losses would be limited by the belief that maternal employment is harmful to children, a belief that has been associated with low rates of maternal employment. 19 Thus, the goal of the present study was to examine pathways linking within-person changes in income and women’s depressive symptoms during the first 3 years after childbirth, as well as variations in the association between income and depressive symptoms across demographic and psychological characteristics of women.
