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Open Access Highly Accessed Research article

Depression and body mass index, a u-shaped association

Leonore M de Wit1*, Annemieke van Straten1, Marieke van Herten2, Brenda WJH Penninx3 and Pim Cuijpers1

Author Affiliations

1 Department of Clinical Psychology and EMGO-Institute, VU University Amsterdam, van der Boechorststraat 1, 1081 BT, Amsterdam, The Netherlands

2 Division of Social and Spatial Statistics, Statistics Netherlands, Heerlen, The Netherlands

3 Department of Psychiatry and EMGO-Institute, VU University Medical Centre, Amsterdam, The Netherlands

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BMC Public Health 2009, 9:14  doi:10.1186/1471-2458-9-14

Published: 13 January 2009

Abstract

Background

Results of studies concerning the association between obesity and depression are conflicting. Some find a positive association, some a negative association and some find no association at all. Most studies, however, examine a linear association between Body Mass Index (BMI) and depression. The present study investigates if a nonlinear (U-shaped) trend is preferable over a linear trend to describe the relationship between BMI and depression, which means that both underweight and obesity are associated with depression.

Methods

We investigated the existence of such a U-curve in a sample of 43,534 individuals, aged between 18–90 years, who participated in a cross-sectional study (Continuous Survey of Living Conditions) of physical and mental health in the general population of the Netherlands. We calculated linear and nonlinear (quadratic) ANOVA with polynomial contrast and curve fit regression statistics to investigate whether there was a U-shaped trend in the association between BMI and depression.

Results

We find a very significant U-shaped association between BMI categories (underweight, normal, overweight and obesity) and depression (p ≤ 0.001). There is a trend indicating a significant difference in the association between males and females (p = 0.05). We find a very significant U-shaped (quadratic) association between BMI (BMI2) and depression (p ≤ 0.001), continuous BMI is not linearly associated with depression (p = 0.514).

Conclusion

The results of this study give evidence for a significant U-shaped trend in the association between BMI and depression.