Objective: To study how stress, life satisfaction and personality related factors, are related to long-term major weight gain.
Design: Prospective cohort study, with follow-up by questionnaire at 6 y and 15 y with a within-study replication.
Subjects: 5867 twin pairs aged 18-54 y at baseline, considered as two sets of unrelated individuals in analyses.
Main outcome measures: Adjusted odds ratios (OR) for 10 kg weight gain over 6 y and 15 y.
Results: A high level of stress at baseline, was a predictor for major weight gain over 6 y, and this effect was consistent in some groups even over 15 y. Low levels of life satisfaction and high scores for neuroticism, were predictors for weight gain in older women. These effects were consistent, even after adjustments for confounding variables (education, dieting, smoking, alcohol consumption and pregnancy in women). High levels of extroversion showed a trend towards lesser weight gain in younger men.
Conclusion: Psychological traits did not affect the risk of major long-term weight gain in a uniform fashion. The observed effects of the factors related to psychological health were modest and consistent, but varied by age and gender. Thus, there may be trait-specific effects in selected subgroups of the population that should be further investigated.