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The Association Between Maternal Age and Depression

      Abstract

      Objective

      Postpartum depression is a relatively common and potentially debilitating condition but its relationship with advanced maternal age has not been adequately studied. We evaluated the relationship between age and depression in a population-based sample of Canadian women.

      Methods

      Data on women aged 20 to 44 years were obtained from the Canadian Community Health Survey, 2007 to 2008. Depression was defined using the Short-Form score from the Composite International Diagnostic Interview (depression defined as a score of5). Women were stratified according to whether they had a live birth within five years preceding the interview. Logistic regression was used to compare the prevalence of depression among women of advanced maternal age versus younger women after adjusting for education, marital status, and chronic disease.

      Results

      Among women who had delivered recently, 8.0% (207 of 2326) were depressed compared with 10% (597 of 5610) of women who had not recently delivered. The prevalence of depression in women who had recently delivered was significantly higher in women aged 40 to 44 years than in women aged 30 to 35 years (adjusted OR 3.72; 95% CI 2.15 to 6.41). Depression rates were not higher among older women who had not had a recent delivery (adjusted OR among women 40 to 44 years 0.75; 95% CI 0.56 to 1.01).

      Conclusion

      Women of advanced maternal age have significantly higher rates of depression than younger women. Research is required to determine if a program of targeted depression screening and prevention will help reduce the burden of illness among older mothers.

      Résumé

      Objectif

      La dépression postpartum est un trouble relativement courant et potentiellement débilitant. Toutefois, son lien avec l’âge maternel avancé n’a pas été examiné de manière adéquate. Nous avons évalué le lien qui existe entre l’âge et la dépression au sein d’un échantillon fondé sur une population de Canadiennes.

      Méthodes

      Nous avons obtenu des données portant sur des femmes âgées de 20 à 44 ans à partir de l’Enquête sur la santé dans les collectivités canadiennes (2007 à 2008). La définition de la dépression a été établie à l’aide de la cote du Short-Form Health Survey de la Composite International Diagnostic Interview (une cote5 indique qu’il y a présence de dépression). Les femmes ont été réparties en fonction de la présence ou de l’absence d’une naissance vivante au cours des cinq années ayant précédé l’entrevue. Une régression logistique a été utilisée pour comparer la prévalence de la dépression chez les femmes d’âge maternel avancé et chez les femmes plus jeunes, à la suite de la neutralisation de l’effet du niveau de scolarité, de l’état civil et de la présence d’une maladie chronique.

      Résultats

      Huit pour cent des femmes qui avaient accouché récemment (207 participantes sur 2 326) étaient déprimées, par comparaison avec 10 % (597 participantes sur 5 610) des femmes qui n’avaient pas accouché récemment. La prévalence de la dépression chez les femmes qui avaient récemment accouché était nettement plus élevée chez les femmes âgées de 40 à 44 ans que chez les femmes âgées de 30 à 35 ans (RC corrigé, 3,72; IC à 95 %, 2,15 - 6,41). Chez les femmes d’âge plus avancé qui n’avaient pas accouché récemment, les taux de dépression n’étaient pas plus élevés (RC corrigé chez les femmes âgées de 40 à 44 ans, 0,75; IC à 95 %, 0,56 - 1,01).

      Conclusion

      Les femmes d’âge maternel avancé présentent des taux considérablement plus élevés de dépression que les femmes moins âgées. Des recherches plus poussées sont nécessaires en vue de déterminer si un programme ciblé de dépistage et de prévention de la dépression peut permettre de réduire le fardeau de la maladie chez les mères d’âge plus avancé.

      Key Words

      ABBREVIATIONS

      AMA
      advanced maternal age
      aOR
      adjusted odds ratio
      CIDI-SF
      Composite International Diagnostic Interview—Short Form

      INTRODUCTION

      The frequency of women giving birth at advanced maternal age (≥35 years) has been on the rise in most high-income countries over the last 30 years.
      • Benzies K.M.
      Advanced maternal age: are decisions about the timing of child-bearing a failure to understand the risks?.
      • Canadian Institute for Health Information
      • Public Health Agency of Canada
      In Canada, between 1995 and 2009, the number of live births per 1000 women aged 35 to 39 years increased by 81% (from 28.0 to 50.6 per 1000 females).
      • Statistics Canada
      Increasing maternal age has become an issue of public health concern because women of advanced maternal age experience higher rates of pregnancy complications, obstetrical intervention, and severe maternal morbidity than younger mothers.
      • Canadian Institute for Health Information
      • Joseph K.S.
      • Allen A.C.
      • Dodds L.
      • Turner L.A.
      • Scott H.
      • Liston R.
      The perinatal effects of delayed childbearing.
      • Bayrampour H.
      • Heaman M.
      Comparison of demographic and obstetric characteristics of Canadian primiparous women of advanced maternal age and younger age.
      • Carolan M.
      • Frankowska D.
      Advanced maternal age and adverse perinatal outcome: a review of the evidence.
      Numerous studies have demonstrated associations between AMA and chromosomal abnormalities, gestational diabetes, multiple births, Caesarean section, preterm birth, low birth weight, and perinatal death.
      • Joseph K.S.
      • Allen A.C.
      • Dodds L.
      • Turner L.A.
      • Scott H.
      • Liston R.
      The perinatal effects of delayed childbearing.
      • Carolan M.
      • Frankowska D.
      Advanced maternal age and adverse perinatal outcome: a review of the evidence.
      • Bayrampour H.
      • Heaman M.
      Advanced maternal age and the risk of cesarean birth: a systematic review.
      • Huang L.
      • Sauve R.
      • Birkett N.
      • Fergusson D.
      • van Walraven C.
      Maternal age and risk of stillbirth: a systematic review.
      • Jacobsson B.
      • Ladfors L.
      • Milsom I.
      Advanced maternal age and adverse perinatal outcome.
      • Lisonkova S.
      • Paré E.
      • Joseph K.S.
      . Does advanced maternal age confer a survival advantage to infants born at early gestation?.
      However, despite the abundance of research aimed at understanding the physiological effects of AMA, few studies have comprehensively examined postnatal depression and the psychological experiences of older mothers. The importance of postpartum depression is underscored by its frequency (10% to 15% of women experience depression after childbirth) and its debilitating effects on the mother and the infant.
      • O’Hara M.W.
      • Swain A.M.
      Rates and risk of postpartum depression— a meta-analysis.
      The anxiety-provoking “high risk” context of pregnancy in women of AMA and the frequency of medical complications have been suggested as reasons to expect higher rates of depression among older mothers.
      • Milgrom J.
      • Gemmill A.W.
      • Bilszta J.L.
      • Hayes B.
      • Barnett B.
      • Brooks J.
      • et al.
      Antenatal risk factors for postnatal depression: a large prospective study.
      On the other hand, the higher and more stable socioeconomic status that often characterizes women of AMA
      • Bayrampour H.
      • Heaman M.
      Comparison of demographic and obstetric characteristics of Canadian primiparous women of advanced maternal age and younger age.
      • Stein Z.
      • Susser M.
      The risks of having children in later life. Social advantage may make up for biological disadvantage.
      could confer psychological benefits.
      • Stein Z.
      • Susser M.
      The risks of having children in later life. Social advantage may make up for biological disadvantage.
      Previous studies on depression in older mothers have yielded mixed results, with some finding negative associations between maternal age and depression,
      • McMahon C.A.
      • Boivin J.
      • Gibson F.L.
      • Fisher J.R.W.
      • Hammarberg K.
      • Wynter K.
      • et al.
      Older first-time mothers and early postpartum depression: a prospective cohort study of women conceiving spontaneously or with assisted reproductive technologies.
      • McMahon C.A.
      • Boivin J.
      • Gibson F.L.
      • Hammarberg K.
      • Wynter K.
      • Saunders D.
      • et al.
      Age at first birth, mode of conception and psychological wellbeing in pregnancy: findings from the parental age and transition to parenthood Australia (PATPA) study.
      • Waldron I.
      • Weiss C.C.
      • Hughes M.E.
      Interacting effects of multiple roles on women’s health.
      • Williams S.
      • McGee R.
      • Olaman S.
      • Knight R.
      Level of education, age of bearing children and mental health of women.
      others observing no differences between age groups,
      • Aasheim V.
      • Waldenström U.
      • Hjelmstedt A.
      • Rasmussen S.
      • Pettersson H.
      • Schytt E.
      Associations between advanced maternal age and psychological distress in primiparous women, from early pregnancy to 18 months postpartum: psychological distress in older first time mothers.
      and yet others showing higher rates of depression in women of AMA.
      • Mirowsky J.
      • Ross C.E.
      Depression, parenthood, and age at first birth.
      • Spence N.J.
      The long-term consequences of childbearing: physical and psychological well-being of mothers in later life.
      • Carlson D.L.
      Explaining the curvilinear relationship between age at first birth and depression among women.
      In addition, a few studies have examined the effects of childbearing on depression by contrasting postpartum women with those who had not recently delivered.
      • Eberhard-Gran M.
      • Eskild A.
      • Tambs K.
      • Samuelsen S.O.
      • Opjordsmoen S.
      Depression in postpartum and non-postpartum women: prevalence and risk factors.
      • O’Hara M.W.
      • Zekoski E.M.
      • Philipps L.H.
      • Wright E.J.
      Controlled prospective study of postpartum mood disorders: comparison of childbearing and nonchildbearing women.
      • Cox J.L.
      • Murray D.
      • Chapman G.
      A controlled study of the onset, duration and prevalence of postnatal depression.
      • Augusto A.
      • Kumar R.
      • Calheiros J.M.
      • Matos E.
      • Figueiredo E.
      Post-natal depression in an urban area of Portugal: comparison of childbearing women and matched controls.
      However, none of these studies have simultaneously compared the effect of age on depression in women who had recently delivered and in women who had not recently experienced childbirth.
      We carried out a population-based study on the effect of age on depression with the objective of comparing the prevalence of depression among younger and older women who either had or had not recently given birth.

      METHODS

      Data for this study were obtained from the Canadian Community Health Survey, 2007 to 2008. This is a nationally representative cross-sectional study that collects data on health status, health care use, and determinants of health on an ongoing basis. The target population included individuals aged 12 years and older living in private dwellings in Canada’s 10 provinces and three territories. Individuals were excluded if they lived in institutions, on First Nations reserves, on government-owned land, or in very remote regions. The survey represented approximately 98% of the Canadian population aged 12 and over.
      • Mirowsky J.
      • Ross C.E.
      Depression, parenthood, and age at first birth.
      It employed a multistage sampling strategy to select households randomly. Approximately one half of the interviews were conducted in person using computer-assisted personal interviews, while the other half were conducted by telephone using computer-assisted telephone interviews. Further details on the methodology of the Canadian Community Health Survey are reported elsewhere.
      • Statistics Canada
      Our study was restricted to women aged 20 to 44 years and was stratified by the experience of recent childbirth based on the response to the question “Have you given birth in the past five years (not including stillbirths)?” The study population was further restricted to women from the six provinces that included the optional depression module in the 2007 to 2008 Canadian Community Health Survey (Nova Scotia, New Brunswick, Quebec, Alberta, Yukon, and Nunavut). Respondents with incomplete information were excluded (n=42). Our final study population included 7936 women; of these, 2326 had given birth in the last five years, and 5610 had not (subsequently referred to as the “recent birth group” and the “no recent birth group,” respectively).
      Age was classified into five-year categories (20 to 24, 25 to 29, 30 to 34, 35 to 39, and 40 to 44 years). The age category 30 to 34 years was used as the reference group since previous research has suggested that rates of depression are lowest at approximately age 30.
      • Mirowsky J.
      • Ross C.E.
      Depression, parenthood, and age at first birth.
      Because the survey question asked women if they had given birth in the last five years, women in the 30 to 34 years of age category in the recent birth group could have delivered a live baby at any time between the ages of 25 and 34. Similarly, women in the 40 to 44 years of age group could have had a live birth at any time between the ages of 35 and 44. Thus, the age group that corresponded to women of AMA was the group aged 40 to 44 in the “recent birth group.” The 35 to 39 years of age group contained some women aged35 at delivery, but also included women aged 30 to 34.
      Data on the prevalence of depression were collected using a short-form scale of items from the Composite International Diagnostic Interview.
      • Statistics Canada
      The CIDI-SF is a widely used structured diagnostic instrument designed to produce diagnoses according to the definitions and criteria of the Diagnostic and Statistical Manual of Mental Disorders, Fourth edition, and the International Classification of Diseases-10th Revision Classification of Mental and Behavioral Disorders.
      • Kessler R.C.
      • Andrews G.
      • Mroczek D.
      • Ustun B.
      • Wittchen H.-U.
      The World Health Organization Composite International Diagnostic Interview short-form (CIDI-SF).
      Scores on the CIDI-SF scale range from 0 to 8, with higher scores indicating higher levels of depression. Individuals with a score of5 are considered to have at least a 90% probability of having had a major depressive episode in the preceding 12 months.
      • Statistics Canada
      • Kessler R.C.
      • Andrews G.
      • Mroczek D.
      • Ustun B.
      • Wittchen H.-U.
      The World Health Organization Composite International Diagnostic Interview short-form (CIDI-SF).
      In this study, depressed individuals were defined as those with a CIDI-SF score of5 and non-depressed individuals as those with a score of<5.
      Subject characteristics known to be associated with age and depression were controlled for in the analysis to provide an adjusted estimate of the association. These included highest level of education attained, marital status, and chronic disease status.
      The prevalence of depression in each age group was calculated, and the results were stratified by recent childbirth status. Bivariable analyses were performed in each stratum to assess the relationship between age and depression and between other subject characteristics and depression. The statistical significance of differences in depression rates between age groups was assessed using the Pearson’s chi-square test. The associations between age groups and depression were reported using crude odds ratios with 95% confidence intervals.
      Multivariable logistic regression was used to measure the presence and strength of the association between age group and depression while controlling for the effect of potential confounders. After testing for possible interactions, all covariates tested in the bivariable analysis were included in the final model to obtain adjusted ORs and 95% CIs. All statistical tests were two-sided and considered significant if the P value was<0.05. Weights reflecting the survey sampling strategy were used in the analysis to account for the individual and household sampling probability and non-response.
      • Statistics Canada
      The relationship between age and depression was further examined using the entire study population of 7936 women. In this analysis, logistic regression was used to test whether recent childbirth significantly modified the effect of age on depression (by introducing interaction terms [age×recent childbirth] into the multiple regression analysis).
      A subgroup analysis was also carried out to quantify the relationship between maternal age and depression in primiparous women. Since information on parity was not directly available in the data source, primiparous women were identified on the basis of household structure (e.g., parent living with spouse and children, single parent living with children) and the number of people living in the household. We carried out a supplementary analysis adjusting for available information on family income (missing for over 10% of subjects) to ascertain whether the inclusion of income affected the study results. Data were analyzed using SAS version 9.3 for Windows (SAS Institute Inc., Cary, NC).
      Ethics approval for this study was not required as the data are publicly accessible.

      RESULTS

      Among the 2326 women in the “recent birth group,” more than 80% were between 25 and 39 years of age, 74% were post-secondary graduates, 55% were married, and 40% reported having a diagnosed chronic disease (Table 1). In comparison, the “no recent birth group” was characterized by being more evenly distributed across all five age categories and having a lower marriage rate (30%, Table 1). Of the women in the “recent birth group,” 8.0% (207 of 2326) were depressed, compared with 10% (597 of 5610) among the “no recent birth group.” Rates of depression by age and recent childbirth status are presented in the Figure.
      Table 1Bivariable associations with depression among Canadian women aged 20 to 44 (n=7936)
      CharacteristicRecent birth group (n=2326)No recent birth group (n=5610)
      DepressedDepressed
      Yes, %No, %PYes, %No, %P
      n%(n=207)(n=2119)n%(n =597)(n=5013)
      Age, years< 0.0010.002
       20 to 242279.410.090.0102922.910.189.9
       25 to 2968427.810.689.498317.712.587.5
       30 to 3477832.05.794.395414.610.289.8
       35 to 3948522.94.096.0114117.89.890.2
       40 to 441528.017.083.1150327.17.892.2
      Highest level education0.030.008
      <Secondary1908.511.488.64096.211.888.3
       Secondary graduate30011.410.289.870812.410.689.4
       Some post-secondary1606.611.588.54979.613.286.8
       Post-secondary graduate167673.56.993.1399671.99.190.9
      Marital status< 0.001< 0.001
       Single/never married2779.018.781.4225438.412.687.4
       Widowed/separated/divorced1164.116.983.14677.018.781.3
       Common-law73732.48.691.4129124.38.391.7
       Married119654.55.294.9159830.35.694.4
      Chronic disease< 0.001<0.001
       Yes98639.813.186.9268144.513.286.8
       No134060.24.695.4292955.57.292.8
      All “Not stated” responses were removed from this table. These responses made up <1% of the responses in each characteristic. Differences between groups are reported using Pearson’s chi-square test statistic. All frequencies reported are unweighted; all proportions and P values are weighted.
      In the “recent birth group” women in all age categories except for women aged 35 to 39 years had significantly higher odds of depression than women in the reference age group (30 to 34 years) (Table 2). The increase in odds was most pronounced among women aged 40 to 44 years (OR 3.40; 95% CI 2.01 to 5.77). Among women in the “no recent birth group,” age was not associated with depression. Higher education level, being married, and not having a chronic disease diagnosis all decreased the odds of depression in both groups of women.
      Table 2Results of logistic regression showing effects of age and other factors on depression among women who had and did not have a live birth in the previous five years
      DeterminantsRecent birth groupNo recent birth group
      UnadjustedAdjustedUnadjustedAdjusted
      OR95% CIOR95% CIOR95% CIOR95% CI
      Age, years
       20 to 241.841.03 to 3.291.010.52 to 1.960.980.74 to 1.310.840.62 to 1.14
       25 to 291.981.29 to 3.031.791.15 to 2.791.260.94 to 1.681.270.95 to 1.71
       30 to 34REFREFREFREFREFREFREFREF
       35 to 390.700.40 to 1.240.740.41 to 1.320.950.70 to 1.280.990.73 to 1.35
       40 to 443.402.01 to 5.773.722.15 to 6.410.740.55 to 0.980.750.56 to 1.01
      Highest level education
      <Secondary1.731.04 to 2.891.150.65 to 2.041.330.95 to 1.861.310.93 to 1.85
       Secondary graduate1.540.96 to 2.461.290.78 to 2.131.180.91 to 1.531.260.96 to 1.64
       Some post-secondary1.750.99 to 3.091.220.66 to 2.241.521.16 to 1.981.361.03 to 1.79
       Post-secondary graduateREFREFREFREFREFREFREFREF
      Marital status
       Single/never married4.232.67 to 6.693.592.15 to 6.012.411.90 to 3.052.291.76 to 2.99
       Widowed/separated/divorced3.751.99 to 7.063.721.92 to 7.233.862.80 to 5.303.942.83 to 5.45
       Common-law1.741.19 to 2.551.521.02 to 2.271.511.15 to 1.981.381.03 to 1.83
       MarriedREFREFREFREFREFREFREFREF
      Chronic disease
       Yes3.122.23 to 4.383.012.13 to 4.261.971.65 to 2.342.021.69 to 2.41
       NoREFREFREFREFREFREFREFREF
      REF: reference category
      Figure thumbnail fx1
      Weighted distribution of depression by age among Canadian women aged 20 to 44 (n=7936)
      Conversely, in the adjusted model for the “no recent birth group,” the absence of an association between maternal age and depression persisted (Table 2). Education, marital status, and chronic disease were significant predictors of depression; however, they had little effect on the association between maternal age and depression. Being widowed, separated, or divorced was the strongest predictor of depression, with an aOR of 3.94 (95% CI 2.83 to 5.45).
      Analysis with an interaction term included in the full model showed that the relationship between older age (40 to 44 years) and depression was modified by having had a recent delivery (P for interaction term<0.001) (Table 3).
      Table 3Results of logistic regression showing adjusted effects of age and other factors on depression among Canadian women aged 20 to 44 (n=7936)
      DeterminantsAdjusted
      OR95% CI
      Age, years
       20 to 240.820.61 to 1.11
       25 to 291.260.94 to 1.69
       30 to 34REFREF
       35 to 391.000.73 to 1.36
       40 to 440.760.56 to 1.02
      Recent childbirth
       Yes0.750.50 to 1.13
       NoREFREF
      Age×Recent childbirth (interaction)
      The effect of older age (i.e., 40 to 44 vs. 30 to 34 years) on depression among women with no recent childbirth is expressed by the odds ratio 0.76; 95% CI 0.56 to 1.02, and this effect was not statistically significant. The effect of older age (i.e., 40 to 44 vs. 30 to 34 years) on depression among women with a recent childbirth is expressed by the product of 2 odds ratios 0.76×4.75=3.61. The P value associated with the interaction term was<0.001, showing that recent childbirth signifcantly modified the effect of older age on depression.
       20 to 24×recent childbirth1.410.73 to 2.75
       25 to 29×recent childbirth1.440.85 to 2.44
       30 to 34×recent childbirthREFREF
       35 to 39×recent childbirth0.720.38 to 1.39
       40 to 44×recent childbirth4.752.75 to 8.78
      Highest level of education
      <Secondary1.290.96 to 1.72
       Secondary graduate1.281.01 to 1.61
       Some post-secondary1.321.03 to 1.70
       Post-secondary graduateREFREF
      Marital status
       Single/never married2.501.98 to 3.15
       Widowed/separated/divorced3.972.97 to 5.29
       Common-law1.431.14 to 1.80
       MarriedREFREF
      Chronic disease
       Yes2.211.89 to 2.59
       NoREFREF
      REF: reference category
      * The effect of older age (i.e., 40 to 44 vs. 30 to 34 years) on depression among women with no recent childbirth is expressed by the odds ratio 0.76; 95% CI 0.56 to 1.02, and this effect was not statistically significant. The effect of older age (i.e., 40 to 44 vs. 30 to 34 years) on depression among women with a recent childbirth is expressed by the product of 2 odds ratios 0.76×4.75=3.61. The P value associated with the interaction term was<0.001, showing that recent childbirth signifcantly modified the effect of older age on depression.
      In the subgroup analyses restricted to primiparous women (n=723), the odds of depression were not significantly elevated in the 20 to 24, 25 to 29, and 35 to 39 years of age groups, compared with the 30 to 34 years of age group. However, the odds of depression in the 40 to 44 years of age group were substantially higher than the odds of depression among women aged 30 to 34 years (aOR 9.51; 95% CI 3.41 to 26.54).
      When income was included in the regression models, the results did not change appreciably. In the adjusted model for the “recent birth group,” women aged 25 to 29 and 40 to 44 years remained significantly more depressed than women aged 30 to 34 years. In the “no recent birth group” there was no significant difference in depression among any of the age groups in the adjusted model. Marital status, chronic disease, and income were significantly associated with depression among women in the “recent birth group” and the “no recent birth group.”

      DISCUSSION

      Our study on the effect of age on depression showed significantly higher rates of depression among women who gave birth between 35 and 44 years of age than women who gave birth in younger age groups. This relationship was strengthened after controlling for the confounding effects of educational level, marital status, and chronic disease. On the other hand, there was no appreciable difference in the prevalence of depression between any of the age categories in the “no recent birth group.” This suggests that the combination of childbirth and AMA accounts for the elevated risk of depression in women aged 35 to 44 years.
      The results of this study are consistent with a growing body of literature suggesting an increased risk of depression in women of AMA.
      • Aasheim V.
      • Waldenström U.
      • Hjelmstedt A.
      • Rasmussen S.
      • Pettersson H.
      • Schytt E.
      Associations between advanced maternal age and psychological distress in primiparous women, from early pregnancy to 18 months postpartum: psychological distress in older first time mothers.
      • Mirowsky J.
      • Ross C.E.
      Depression, parenthood, and age at first birth.
      • Carlson D.L.
      Explaining the curvilinear relationship between age at first birth and depression among women.
      This increased risk has been attributed to a variety of factors, such as the perception that older women have more difficult experiences and adjustments to motherhood,
      • Bayrampour H.
      • Heaman M.
      • Duncan K.A.
      • Tough S.
      Advanced maternal age and risk perception: a qualitative study.
      and the lack of peer support due to deviations from social norms surrounding maternal age.
      • Carlson D.L.
      Explaining the curvilinear relationship between age at first birth and depression among women.
      Others have suggested that the increase in obstetrical complications, multiple births, and increases in the use of assisted reproductive technologies may contribute to higher rates of depression.
      • McMahon C.A.
      • Boivin J.
      • Gibson F.L.
      • Fisher J.R.W.
      • Hammarberg K.
      • Wynter K.
      • et al.
      Older first-time mothers and early postpartum depression: a prospective cohort study of women conceiving spontaneously or with assisted reproductive technologies.
      On the other hand, it is possible that the higher rates of depression among older mothers are a biological phenomenon involving age and childbearing.
      Our findings contradict studies that have demonstrated a negative relationship between maternal age and depression.
      • McMahon C.A.
      • Boivin J.
      • Gibson F.L.
      • Fisher J.R.W.
      • Hammarberg K.
      • Wynter K.
      • et al.
      Older first-time mothers and early postpartum depression: a prospective cohort study of women conceiving spontaneously or with assisted reproductive technologies.
      • McMahon C.A.
      • Boivin J.
      • Gibson F.L.
      • Hammarberg K.
      • Wynter K.
      • Saunders D.
      • et al.
      Age at first birth, mode of conception and psychological wellbeing in pregnancy: findings from the parental age and transition to parenthood Australia (PATPA) study.
      • Williams S.
      • McGee R.
      • Olaman S.
      • Knight R.
      Level of education, age of bearing children and mental health of women.
      Authors of these studies propose that the favourable socioeconomic characteristics of older mothers (e.g., more financial security) together with factors relating to maturity (e.g., stability of relationship) are protective against depression. Although our study consisted predominantly of women of high socioeconomic status, it is possible that biological risk factors among women of AMA limited any psychosocial benefits of childbearing at older age.
      • Mirowsky J.
      • Ross C.E.
      Depression, parenthood, and age at first birth.
      Differences in the assessment of depression using different depression measures at different times in the parenting cycle may also have contributed to inconsistent findings between studies. Our study used the CIDI-SF, but others have used the Edinburgh Depression Scale, symptom checklists, other diagnostic interviews, and behavioural indexes of stress/coping.
      • McMahon C.A.
      • Boivin J.
      • Gibson F.L.
      • Fisher J.R.W.
      • Hammarberg K.
      • Wynter K.
      • et al.
      Older first-time mothers and early postpartum depression: a prospective cohort study of women conceiving spontaneously or with assisted reproductive technologies.
      • McMahon C.A.
      • Boivin J.
      • Gibson F.L.
      • Hammarberg K.
      • Wynter K.
      • Saunders D.
      • et al.
      Age at first birth, mode of conception and psychological wellbeing in pregnancy: findings from the parental age and transition to parenthood Australia (PATPA) study.
      • Williams S.
      • McGee R.
      • Olaman S.
      • Knight R.
      Level of education, age of bearing children and mental health of women.
      • Aasheim V.
      • Waldenström U.
      • Hjelmstedt A.
      • Rasmussen S.
      • Pettersson H.
      • Schytt E.
      Associations between advanced maternal age and psychological distress in primiparous women, from early pregnancy to 18 months postpartum: psychological distress in older first time mothers.
      In contrast to previous work,
      • Aasheim V.
      • Waldenström U.
      • Hjelmstedt A.
      • Rasmussen S.
      • Pettersson H.
      • Schytt E.
      Associations between advanced maternal age and psychological distress in primiparous women, from early pregnancy to 18 months postpartum: psychological distress in older first time mothers.
      • Mirowsky J.
      • Ross C.E.
      Depression, parenthood, and age at first birth.
      we did not observe an increased rate of depression in adolescent mothers. The inclusion of both education and marital status in our model may account for this inconsistency. Adolescent mothers may not yet have had the opportunity to attain higher educational status or to marry. Therefore, controlling for these variables may have masked a true effect, and the unadjusted estimate (OR 1.84; 95% CI 1.03 to 3.29) may be the more appropriate measure for this age category.
      The key strengths of this study were the large study size, the use of a validated instrument to measure the outcome variable, and the inclusion of socioeconomic status and chronic disease indicators into the analytic model. Limitations of the study include the cross-sectional nature of the design and the measures based on self-report, which may be susceptible to social desirability and recall biases. Another limitation of our study is the lack of a direct parity measure and our use of a proxy measure to identify primiparous women.

      CONCLUSION

      Our population-based study provides evidence of a strong positive association between AMA and depression, even after adjustment for education, marital status, and chronic disease. Further research is required to assess the effect of pregnancy complications and assisted reproductive technology on the risk of experiencing depression. Research is also required to determine if a program of targeted depression screening and prevention will help reduce the burden of illness among older mothers.

      ACKNOWLEDGEMENTS

      We thank Dr Mieke Koehoorn for providing helpful feedback and guidance on the study design and the manuscript. Giulia Muraca is the recipient of the Vanier Canada Graduate Scholarship and is also supported by a Canadian Institutes of Health Research (CIHR) team grant on severe maternal morbidity. KS Joseph is supported by a CIHR Chair in maternal, fetal and infant health services research.

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