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Overweight or obese young people are not at increased risk of depression, but young people with depression are at increased risk of obesity
  1. Angela L Wilson,
  2. Gary S Goldfield
  1. Department of Psychology, University of Ottawa, Ottawa, Ontario, Canada
  1. Correspondence to: Dr Gary Goldfield, Healthy Active Living and Obesity Research Group, Children's Hospital of Eastern Ontario Research Institute, 401 Smyth Rd, Ottawa, ON, Canada K1H 8L1; ggoldfield{at}cheo.on.ca

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Implications for practice and research

  • Health professionals working with young people who have major depression should be aware that they may be at increased risk for developing obesity over time, particularly boys.

  • Public health promotion or prevention efforts directed towards youths experiencing clinical depression may help to reduce future weight issues.

Context

Obesity and depression have both been associated with adverse health outcomes in young people.1 A growing body of evidence has investigated whether a link exists between these two conditions, suggesting that one may act as a risk factor for the other. To date, the evidence about the nature and strength of this relationship has been mixed, with the majority of studies examining the link in only one direction and overlooking the influence of mediating and moderating variables.2 Roberts and Duong explored prospectively the reciprocal relationship between obesity and depression in adolescents, while controlling for known covariates.

Methods

A community-based sample of 4175 youths aged 11–17 years were interviewed using a validated, structured measure (youth version of the Diagnostic Interview Schedule for Children-Version IV), and their height and weight were measured. Repeat measures were taken approximately 12 months later from 3134 youths, representing a 75% retention rate at follow-up. The 12-month prevalence of mood disorders, major depression and depressive symptoms was assessed according to Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition diagnostic criteria, while weight status (normal weight, overweight or obese) was calculated using the Centers for Disease Control and Prevention growth charts. ORs were calculated to determine the degree to which depression increased the odds of obesity, and vice versa, at baseline and from baseline to 12-month follow-up. These ratios were derived from logistic regression analyses, and were adjusted to control for relevant covariates including age, gender, family income, diet and self-reported physical activity.

Findings

Mood disorders and major depression, but not depressive symptoms, were positively correlated with weight status at baseline. Weight status at baseline did not significantly predict clinical or subclinical levels of depression at 12-month follow-up. The presence of major depression or any mood disorder (but not depressive symptoms) at baseline predicted a significant increased risk for obesity (OR=2.1 to 2.9), but not overweight, at follow-up. Gender analyses revealed this effect to be significant only for boys (OR=6.0). The authors concluded that obese youths are not more likely to become depressed but depressed youths are more likely to become obese.

Commentary

Roberts and Duong's study is the first to prospectively explore the reciprocal relationship between obesity and depression in youth. The use of validated diagnostic interviews, objective measures of height and weight, a large and representative sample, and controlling for known confounders are significant methodological strengths.3 The results suggest that among young people, particularly boys, major depression is a risk factor for developing obesity 1 year later, while the reverse was not found to be true. Interestingly, this relationship was identified after controlling for baseline weight status, indicating that depressed youths are at risk for obesity, but not overweight. Given the cumulative, progressive nature of obesity onset, an analysis of weight gain or change in body mass index would aid the interpretation of these findings.

Though the data suggest that depression leads to obesity, it may be premature to conclude that obesity does not lead to depression. As the authors indicated, a 1-year follow-up period may have prevented the observation of weight status increasing the risk of depression. It is likely that temporal differences exist in the development, progression and remission of depression and obesity, and a longer follow-up period would be beneficial in deciphering directionality. Additionally, direct tests of the ORs would provide a more definitive evaluation of whether the strength of directionality of the obesity–depression relationship differs.

These initial findings provide valuable data which lend support to directing obesity prevention strategies towards youths suffering with depression, especially boys, potentially by focusing on fostering healthy lifestyle choices. However, the weight of evidence is not yet sufficient to eliminate obesity as a risk factor for the development of depression over a longer time period. Subsequent research should continue to investigate the temporal patterning of the obesity–depression link, and identify mediators and moderators to elucidate a better understanding of this complex relationship.

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Footnotes

  • Competing interests None.

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