The overweight/obesity - depression links over the life course

Abstract

Background and aims Worldwide, the prevalence of overweight, obesity and depression are increasing in both males and females and across different age groups. Although an increasing number of studies have examined their association, the results of these studies are mixed and therefore do not allow any firm conclusions to be drawn about either the strength or direction of any associations. One potential explanation is that there are relatively few cohort studies available, with sufficiently long follow-up periods that also have data on both depression and obesity as well as on potential confounding factors. The aim of this study was to examine the longitudinal associations between overweight, obesity and depression, in both adolescents and adults, with a focus on adult women who are increased risk, across their reproductive life course, of overweight, obesity and depression. Methods The first phase of the study comprised two systematic reviews and meta-analyses. Comprehensive computerized literature searches were undertaken using Pubmed (including Medline), PsycINFO, Embase, CINAHL, BIOSIS Preview and the Cochrane Library. A standard data extraction form was used to collect the secondary data for the systematic reviews. For the meta-analyses, a quality effects model was used instead of a random effects model to estimate the pooled effect size this then allowed for an empirical bias adjustment of the studies included in each review. The second phase of the study investigated the longitudinal association between overweight, obesity and depression in adult women and used data from the mothers’ cohort of the Mater University Study of Pregnancy (MUSP), a prospective pre-birth cohort study which began in 1981 at the Mater Hospital in Brisbane, Australia. The baseline sample consisted of 6753 pregnant women attending their first obstetric visit for that pregnancy. These women have been followed up at eight points in time over a 27 year period. The current work uses depression and covariates from every measurement period from pregnancy to 27 years. Body mass index, waist circumference and waist to hip ratio measures were ascertained from the women at baseline and again at the 21 and 27 year follow-ups. A number of statistical and methodological approaches were applied to estimate the longitudinal association between depression and overweight and obesity and to account for attrition occurring over this period. Key findings The first systematic review and meta-analysis examined the association between obesity and depression in adolescents and young adults. It found: 1) a bi-directional association between obesity and depression in adolescence. The association was stronger from depression leading to obesity than for obesity leading to depression. Both males and females were at risk, however; the association was stronger for young adult females. The second systematic review and meta-analysis examined the same association in adulthood, the findings were similar, that is: 2) in adulthood, the strength of the association between obesity and depression was greater from depression leading to obesity. A bidirectional relationship was evident for both men and women, these associations were more pronounced among young and middle aged women and women when followed for longer time periods. The bidirectional associations found in the studies comprising the first phase of this thesis were explored in depth using the MUSP longitudinal data. Three aspects of the association were examined: 1) the first study explored the association between gestational weight gain, postpartum weight retention and adult mental health. Adult women who gained either inadequate weight or excess weight during pregnancy were at an increased risk of lifetime anxiety and of co-morbid anxiety and depression. Women with higher postpartum weight retention were at an increased risk of experiencing depression in the last 12 months and of experiencing lifetime anxiety. 2) The second study examined the effects of the chronicity and severity of depression on obesity, measured using body mass index (BMI) and waist circumference (WC). Women who experienced both chronic and severe depression were at an increased risk of BMI and WC related obesity compared with women with no depression at 27 years postpartum. All these associations were independent of other potential confounding factors. 3) In relation to the timing of depression, two time periods were identified, the first was depression experienced around pregnancy and the early postpartum. The second was depression experienced during the early child-rearing period (when the child was between 5 and 14 years old). Women who were depressed around pregnancy were at an increased risk of obesity 21 years postpartum. Chronic depression, extending from pregnancy through the early child rearing period, increased women’s risk of obesity assessed using WC and waist to hip ratio (WHR) 21 years postpartum. Conclusions Although obesity and depression are bi-directionally associated, over the life course depression has a stronger effect on the development of obesity than obesity has on the development of depression. Appropriate interventions targeting depression may reduce the risk of obesity, particularly in women during their childbearing years.