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 In the development of postpartum depression, the predictive power of maternal mood during the immediate postpartum period (the first 2 weeks postpartum) has consistently been reported. For example, the EPDS (1) was used to measure depressive symptomatology in 217 UK mothers at 5 days and 6 weeks postpartum (2). A significant positive correlation between the 2 EPDS scores was found (r = 0.60, P < 0.001), and of the 25 women who scored above 12 on the EPDS at 6 weeks, 17 (68%) had similar symptomatology in the first week postpartum (that is, a However, despite the concordance in maternal mood across the early postpartum period, researchers and health professionals have traditionally been cautioned against screening for depression in the first couple of weeks postdelivery because a significant number of women identified with depressive symptoms do not remain symptomatic 6 to 8 weeks later (7,8). The primary cause of this false-positive rate is the high prevalence of “postpartum blues,” reported to affect up to 75% of women during the first week postpartum (9). Screening in the immediate postpartum period could therefore result in substantial costs—both economic, in terms of resources required to follow up all cases of positive screens, and maternal, in terms of burden and potential risk associated with implementation of unnecessary interventions for women with false-positive scores. Conversely, early detection from early screening may improve outcomes for women with true-positive scores. This population-based study aimed to determine whether true- and false-positive screening scores can be distinguished during the early postpartum period by examining characteristic differences between 2 groups: 1) women with depressive symptomatology at 1 week postpartum who continued to exhibit symptoms at 8 weeks postpartum, compared with those who did not; and 2) women with depressive symptomatology at 8 weeks postpartum who previously exhibited symptoms at 1 week postpartum, compared with those who did not. MethodSample Participants completed questionnaires as part of a longitudinal study to develop a multifactorial predictive model of postpartum depression (10); the study was conducted in a health region near Vancouver, British Columbia, from April 2001 to January 2002. Eligible women, who were aged at least 18 years and able to understand English, were recruited after the study received approval from the university ethics committee and authorization from the participating health region. To obtain a population-based sample, study packages that included informed consent procedures were provided either antenatally (through participating family physician, obstetrician, and midwifery offices) to women at more than 32 weeks gestation or postnatally during the standard 48-hour posthospital discharge call provided by public health nurses to new mothers. The same questionnaires were mailed to all participants at 1, 4, and 8 weeks postpartum; reminder telephone calls were provided to women who did not return their questionnaires within 2 weeks of mailing. Antenatally, 166 participants were recruited, with 115 (69%) returning the 1-week postpartum questionnaire. Of the approximately 971 women screened postnatally, 857 were eligible. The most common reason for ineligibility was inability to read English (24%). Of the eligible women, 190 (22%) declined enrolment, with the most common reason for declining being lack of interest or time. Of the 667 new mothers who agreed to participate in the study, 479 returned the 1-week postpartum questionnaire, yielding a 72% response rate. In total, 594 participants returned the 1-week postpartum questionnaire. Of these mothers, 535 (90%) returned the 4-week questionnaire, and 498 (84%) returned the 8-week questionnaire. All participants who returned the 1-week postpartum questionnaire were included in this study. Measures Assessment of Depressive Symptomatology. The EPDS (1), a 10-item, self-report instrument, was used to assess depressive symptomatology at 1 and 8 weeks postpartum. Items were rated on a 4-point scale to produce a summative score ranging from 0 to 30, with higher scores indicating lower maternal mood. In this study, women who scored more than 9 on the EPDS were defined as exhibiting depressive symptomatology. This cut-off point has been recommended for community-based screening (11,12) and has been shown to have high sensitivity, specificity, and positive predictive power for postpartum depression (11,13). Maternal Characteristics. To identify maternal characteristics potentially associated with depressive symptomatology, we conducted a literature search of MEDLINE, PubMed, Cinahl, PsycINFO, and EMBASE. Consistently reported risk factors were included in the 1-week postpartum questionnaire, categorized into the following domains: sociodemographic, biological, psychological, psychiatric history, pregnancy-related, life stressors, social support, obstetrical, and maternal adjustment (Table 1). Several risk factors were also quantified according to standardized measures. We used the Vulnerable Personality Style Questionnaire (14), a 9-item Likert-type instrument, to assess personality traits (for example, poor coping style, timidity, worry about what others think, need for order and control in life, perfectionism, quickness to anger with temper outbursts, difficulty asking for help). Items were rated on a
Statistical AnalysisIn this study, we divided participants into 2 groups: 1) women with depressive symptomatology (EPDS score > 9) at 1 week postpartum and 2) women with depressive symptomatology (EPDS score > 9) at 8 weeks postpartum. Women with depressive symptomatology at 1 week postpartum were then subcategorized as follows: women who remained symptomatic (continued EPDS score > 9 at 8 weeks postpartum) and those who did not (EPDS score ≤ 9 at 8 weeks postpartum). Similarly, women with depressive symptomatology at 8 weeks postpartum were subcategorized as follows: women who were previously symptomatic (EPDS score > 9 at 1 week postpartum) and those who were not (EPDS score ≤ 9 at 1 week postpartum). We used chi-square tests to examine differences between 2 groups for dichotomous categorical variables; independent sample t tests were conducted for continuous variables. We used SPSS (Version 11.0 for Windows) to analyze the data. ResultsWomen with Depressive Symptomatology at 1 Week Postpartum At 1 week postpartum, 175 (29.5%) women exhibited depressive symptomatology (EPDS > 9). The mean age of this sample was 28.1 years, SD 4.9, with a range of 17 to 44 years. Eighty-nine percent of the women were white (n = 154), with 88% indicating they were married or living common-law (n = 152). Of the mothers, 39% (n = 68) had a high school diploma or less education; 42% (n = 72) had a college diploma or went to a trade school; and 19% (n = 32) had a university degree or higher education. In relation to annual household income, 48% (n = 78) of mothers had an income less than CDN$40 000; 26% (n = 42) had incomes between $40 000 and $60 000; and 26% (n = 41) had incomes greater than $60 000. Of the women, 47% (n = 83) were primiparous; 71% (n = 123) delivered vaginally; and 63% (n = 110) were discharged home within 48 hours of delivery. Among the mothers with depressive symptomatology at 1 week postpartum, 45.2% (n = 66) had an EPDS score ≤ 9 at 8 weeks postpartum and formed the “nondepressive group,” whereas 54.8% (n = 80) of women had an EPDS score > 9 at 8 weeks postpartum and formed the “depressive group.” Table 2 lists significant group differences in maternal characteristics. In particular, among the sociodemographic variables, the following were associated with a continued EPDS score > 9 at 8 weeks postpartum: born outside Canada, immigration within the last 5 years, and multiparous parity. Biological factors that were significantly different between the 2 groups included number of premenstrual symptoms; significant psychological factors included vulnerable personality and self-esteem. There were also significant differences in relation to depression during pregnancy, history of postpartum depression, and family history of depression in pregnancy. Mothers who continued to exhibit depressive symptomatology at 8 weeks postpartum had significantly higher levels of perceived stress, were more likely to have a partner with a drug or alcohol problem, and were more likely to have been sexually abused as a child. In terms of social support, low perceptions of global support and relationship-specific support from the partner, mother, and other women with children were associated with continued depressive symptomatology at 8 weeks postpartum. These women also had significantly higher levels of conflict with their partners and other women with children and were more likely to report that they had no one available to provide help without asking. There were no group differences in relation to pregnancy, obstetric, or maternal adaptation factors.
Women With Depressive Symptomatology at 8 Weeks Postpartum At 8 weeks postpartum, 101 (20.3%) women exhibited depressive symptomatology (EPDS > 9). The mean age of the sample was 28.8 years, SD 4.9, with a range of 20 to 44 years. Of the women, 91% were white (n = 91), with 94% indicating that they were married or living common-law (n = 94). Forty-two percent (n = 42) of mothers had a high school diploma or less education, 44.4% (n = 44) had a college diploma, and 13.1% (n = 13) had a university degree or higher education. In relation to annual household income, 45.7% (n = 47) of mothers had an income less than CDN$40 000; 29.2% (n = 27) had incomes between $40 000 and $60 000; and 25% (n = 23) had incomes greater than $60 000. Of the women, 38% (n = 39)were primiparous; 59% (n = 59) delivered vaginally; and 67.3% (n = 68) were discharged home within 48 hours of delivery. Among the mothers with depressive symptomatology at 8 weeks postpartum, 20.8% (n = 21) had an EPDS score ≤ 9 at 1 week postpartum and formed the “nondepressive group,” whereas 79.2% (n = 80) of women had an EPDS score > 9 and formed the “depressive group.” Table 3 lists significant group differences in maternal characteristics. In particular, among the sociodemographic variables, being born outside Canada was the only factor associated with a previous EPDS score > 9 at 1 week postpartum. The only significant psychological factor included a vulnerable personality. Mothers who previously exhibited depressive symptomatology at 1 week postpartum also had significantly higher levels of perceived stress and number of stressful life events in the past 12 months, compared with women who did not have depressive symptomatology at 1 week. In terms of social support, low perceptions of global support and relationship-specific support with the mother-in-law were associated with previous depressive symptomatology at 1 week postpartum. These women also had significantly higher levels of conflict with their partners. There were no group differences in relation to biological factors, past psychiatric history, pregnancy, obstetric, or maternal adjustment factors.
DiscussionThis study aimed to determine whether true- and false-positive screening scores can be distinguished during the early postpartum period by examining differences between 1) women with depressive symptomatology at 1 week postpartum who continue to exhibit symptoms at 8 weeks postpartum, compared with those who do not; and 2) women with depressive symptomatology at 8 weeks postpartum who previously exhibited symptoms at 1 week postpartum, compared with those who did not. This is the first known population-based study to specifically examine these differences. Consistent with previous research (7), screening at 1 week postpartum was associated with a high false-positive rate: nearly 50% of women with EPDS scores > 9 at 1 week postpartum no longer screened positive for probable depression at 8 weeks postpartum (EPDS > 9). However,we identified several significant differences between those women whose depressive symptoms continued and those whose symptoms resolved. Several of the variables that differentiated between these 2 groups of women are known risk factors for postpartum depression. In particular, depression during pregnancy has consistently been established as one of the strongest risk factors for postpartum depression (24–26). In about 20% to 30% of cases, women who are identified with postpartum depression report that their symptoms had onset during pregnancy (27,28). It therefore follows that women with persistent depressive symptoms were more likely than women with remitting depression to have reported symptoms of depression during pregnancy. Other known risk factors for postpartum depression that differentiated between the persistent and remitting depressive symptoms groups include vulnerable personality, history of postpartum depression, low self-esteem, perceived stress, and lack of social support (14–29). In addition, women who were born outside Canada and (or) immigrated to Canada within the last 5 years were more likely to exhibit persistent symptoms of depression. This finding is consistent with other recent reports indicating that the prevalence of postpartum depression is high among immigrant populations (10–12,30–32). Other maternal characteristics that differed significantly between the persistent and remitting depression groups—including premenstrual symptoms, history of postpartum depression, and family history of depression during pregnancy—may indicate that women with persistent depression could have an underlying hormonal or genetic vulnerability to perinatal depression. There is evidence that a subgroup of women may be particularly sensitive to the normal hormonal changes that accompany pregnancy and childbirth. For example, Bloch and colleagues found that, when the pregnant and postpartum states were mimicked with exogenous hormones, women with a history of postpartum depression exhibited mood changes, whereas a control group with no history of postpartum depression exhibited no response (33). In addition, women who develop postpartum depression are known to have significantly more first-degree relatives with a history of depression, compared with women who do not develop postpartum depression (18–34). Women who screen positive for depression during the immediate postpartum period and have one or more of these biological risk factors may therefore be more likely to continue to exhibit symptoms of depression later in the postpartum period. Other variables, such as childhood sexual abuse (35), that distinguished between the persistent and remitting depressive symptoms groups are known to be associated with depression in women, independent of childbirth. Considering that major depression is common among women in their childbearing years (36), a proportion of this population-based sample would likely have met criteria for major depression prepregnancy, during pregnancy, and continuing throughout the postpartum period; as such, variables that are associated with chronic major depression would be expected to differentiate between those women whose symptoms of depression continued beyond the immediate postpartum period and those women whose symptoms resolved. Consistent with previous research (3–6,37), nearly 80% of women with elevated EPDS scores at 8 weeks postpartum also had elevated scores in the immediate postpartum period. The variables that differentiated the women with new-onset symptoms of depression from those with persistent symptoms were very similar to the variables identified in the previous analysis of true- and false-positive scores. As would be expected on the basis of the postpartum depression risk-factor literature (26), immigrant status, recent life stressors, perceived stress, low social support, conflict with partner, and a vulnerable personality were also associated with new onset of depressive symptoms at 8 weeks postpartum. Although the EPDS has good sensitivity and specificity when compared with diagnostic clinical interviews, no psychiatric interviews were conducted for this study. Further, there is some possibility for selection bias because only 72% of the mothers returned the first-week postpartum questionnaire. Although this is an exploratory study, a large number of variables were assessed, which possibly led to chance findings. Despite these limitations, the findings confirm that screening for depressive symptoms during the early postpartum period will yield a significant number of false-positive scores, that is, women whose symptoms of depression will spontaneously remit by 8 weeks postpartum. However, our findings also confirm that most women with depressive symptoms later in the postpartum period (8 weeks) can be identified from elevated depression scores in the immediate postpartum period. Strategies to address both the benefits and limitations of early screening are therefore needed. Our data show that several characteristics differentiate women with persistent, compared with remitting, symptoms of depression. These are, primarily, known risk factors for postpartum depression and (or) chronic major depression in women, including depression during pregnancy, lack of perceived social support, and childhood sexual abuse. These findings therefore suggest that, when screening tools are administered during the immediate postpartum period, positive scores should be interpreted in the context of each individual woman’s risk for depression. Many practice settings collect data regarding such risk factors during the prenatal period (using, for example, a psychosocial screening tool such as the Antenatal Psychosocial Health Assessment; 16). Women with a positive screen for depressive symptoms in the immediate postpartum period, together with one or more known risk factors for depression, could then be targeted for further assessment and possible intervention. Further research, including diagnostic assessments of depression and economic evaluations, is required to identify optimal screening procedures for postpartum depression. However, our results suggest that an understanding of a woman’s biological and psychosocial risk for postpartum depression, together with use of a screening tool such as the EPDS, may assist health professionals to identify early symptoms of depression. Funding and SupportDr Dennis received financial support from the Canadian Institutes of Health Research through a postdoctoral research fellowship, as well as financial support from the Hamber Foundation and the Fraser Valley Health Region. References1. Cox JL, Holden JM, Sagovsky R. Detection of postnatal depression. Development of the 10-item Edinburgh Postnatal Depression Scale. Br J Psychiatry 1987;150:782–6. 2. Hannah P, Adams D, Lee A, Glover V, Sandler M. Links between early post-partum mood and post-natal depression. Br J Psychiatry 1992;160:777–80. 3. Dennis CL. Can we identify mothers at risk for postpartum depression in the immediate postpartum period using the Edinburgh Postnatal Depression Scale? J Affect Disord 2004;78:163–9. 4. Yamashita H, Yoshida K, Nakano H, Tashiro N. Postnatal depression in Japanese women—detecting the early onset of postnatal depression by closely monitoring the postpartum mood. J Affect Disord 2000;58:145–54. 5. 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Relationships between childhood maltreatment, adult health and psychiatric outcomes, and medical utilization. J Clin Psychiatry 2004;65(Suppl 12):10–5. 36. Kessler RC, McGonagle KA, Zhao S, Nelson CB, Hughes M, Eshleman S, and others. Lifetime and 12-month prevalence of DSM-III-R psychiatric disorders in the United States. Results from the National Comorbidity Survey. Arch Gen Psychiatry 1994;51:8–19. 37. Henshaw C. Mood disturbance in the early puerperium: a review. Arch Women Ment Health 2003;6(Suppl 2):S33–42. Author(s)Manuscript received September 2005, revised, and accepted January 2006. 1. Assistant Professor, University of Toronto, Toronto, Ontario. 2. Research Scientist, Centre for Addiction and Mental Health, Toronto, Ontario. Address for correspondence: Dr C-L Dennis, University of Toronto, Faculty of Nursing, 155 College Street, Toronto, ON M5T 1P8 e-mail: cindylee.dennis@utoronto.ca
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