ORIGINAL ARTICLE Obesity and depression: results from the longitudinal Northern Finland 1966 Birth Cohort Study A Herva 1 , J Laitinen 2,3 , J Miettunen 1 , J Veijola 4 , JT Karvonen 1 , K La ¨ksy 1 and M Joukamaa 5,6 1 Department of Psychiatry, Oulu University Hospital, Oys, Finland; 2 Department of Public Health, Science and General Practice, University of Oulu, Oulu, Finland; 3 Oulu Regional Institute of Occupational Health, Oulu, Finland; 4 Academy of Finland and Department of Psychiatry, University of Oulu, Oulu, Finland; 5 Department of Social Psychiatry, Tampere School of Public Health, University of Tampere, Tampere, Finland and 6 Department of Psychiatry, Tampere University Hospital, Tampere, Finland Objective: To examine the association between body size and depression in a longitudinal setting and to explore the connection between obesity and depression in young adults at the age of 31 years. Design: This study forms part of the longitudinal Northern Finland 1966 Birth Cohort Study (N ¼ 12 058). The follow-up studies were performed at 14 and 31 years. Data were collected by postal inquiry at 14 years and by postal inquiry and clinical examination at 31 years. Subjects: A total of 8451 subjects (4029 men and 4422 women) who gave a written informed consent and information on depression by three depression indicators at 31 years. Measurements: Body size at 14 (body mass index (BMI) and 31 (BMI and waist-to-hip ratio (WHR)) years and depression at 31 years by three different ways: depressive symptoms by the HSCL-25-depression questionnaire (HSCL-25), the use of antidepressants and self-reported physician-diagnosed depression. Results: Obesity at 14 years associated with depressive symptoms at 31 years; among male subjects using the cutoff point 2.01 in the HSCL-25 (adjusted odds ratio (OR) 1.97, 95% CI 1.06–3.68), among female subjects using the cutoff point 1.75 (adjusted OR 1.64, 95% CI 1.16–2.32). Female subjects who were obese both at baseline and follow-up had depressive symptoms relatively commonly (adjusted OR 1.40, 95% CI 1.06–1.85 at cutoff point 1.75); a similar association was not found among male subjects. The proportion of those who used antidepressants was 2.17-fold higher among female subjects who had gained weight compared to female subjects who had stayed normal-weighted (adjusted OR 2.17, 95% CI 1.28–3.68). In the cross- sectional analyses male subjects with abdominal obesity (WHR X85th percentile) had a 1.76-fold risk of depressive symptoms using the cutoff 2.01 in the HSCL-25 (adjusted OR 1.76, 95% CI 1.08–2.88). Abdominally obese male subjects had a 2.07-fold risk for physician-diagnosed depression (adjusted OR 2.07, 95% CI 1.23–3.47) and the proportion of those who used antidepressants was 2.63-fold higher among obese male subjects than among male subjects without abdominal obesity (adjusted OR 2.63, 95% CI 1.33–5.21). Abdominal obesity did not associate with depression in female subjects. Conclusion: Obesity in adolescence may be associated with later depression in young adulthood, abdominal obesity among male subjects may be closely related to concomitant depression, and being overweight/obese both in adolescence and adulthood may be a risk for depression among female subjects. International Journal of Obesity (2006) 30, 520–527. doi:10.1038/sj.ijo.0803174; published online 15 November 2005 Keywords: depression; body mass index; waist-to-hip ratio; cohort study; longitudinal study Introduction The prevalence of obesity has been increasing both among adults and children in Western countries. 1–3 Obesity is a risk factor for many physical diseases, such as type 2 diabetes 4 and cardiovascular diseases, 5 and can lead to premature death. 6 Especially abdominal obesity, as estimated by the waist-to-hip ratio (WHR), is associated with type 2 diabetes mellitus, cardiovascular disease and stroke. 7,8 Depression is also a common public health problem, and it has been shown to be associated with many somatic disabilities such as cardiovascular diseases and type 2 diabetes. 9,10 In cardiovascular diseases, depression increases mortality and morbidity by mechanisms that are still Received 7 January 2005; revised 26 September 2005; accepted 28 September 2005; published online 15 November 2005 Correspondence: Dr A Herva, Department of Psychiatry, University Hospital of Oulu, PL 26, FIN-90029 Oys, Finland. E-mail: anne.herva@oulu.fi International Journal of Obesity (2006) 30, 520–527 & 2006 Nature Publishing Group All rights reserved 0307-0565/06 $30.00 www.nature.com/ijo