The Causal Effects of Transition into Poverty on Mental Health in the UK Working-Age Population

Thomson, R. M. , Pearce, A. , Leyland, A. and Katikireddi, S. V. (2020) The Causal Effects of Transition into Poverty on Mental Health in the UK Working-Age Population. 16th World Congress on Public Health 2020: Public Health for the future of humanity: analysis, advocacy and action, 12-16 Oct 2020.

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Background: Addressing the impact of poverty through income and welfare policies is likely important for public mental health; however, few studies assess potential effect size using causally-informed methodologies. To provide meaningful information for policymakers, we aimed to estimate the average treatment effect of transitioning into poverty on mental health. Methods: We used data for working-age adults (aged 25-64) from nine waves of the nationally representative UK Household Longitudinal Survey (2009-2019, n = 39,553 obs=155,963). Exposure was transition into poverty (household equiv. income < lt;60% median). Outcome was score ≥4 on General Health Questionnaire-12, indicating likely common mental disorder (CMD). To minimise the influence of reverse causation and time-varying confounders we used a marginal structural modelling (MSM) approach to create inverse probability of treatment weights. We performed secondary analysis stratifying by sex, and calculated population attributable fractions for each model. Results: Good balance of confounders was achieved between exposure groups. Experiencing new poverty was associated with increased odds of CMD (adjusted OR 1.33, 95% CI 1.24-1.42, p < lt; 0.001) with a 4.8% (3.6-6.0) absolute difference in prevalence: 24.0% vs 19.2%. There was a difference in relative effect by sex, with OR 1.40 (1.25-1.56, p < lt; 0.001) for men vs OR 1.28 (1.18-1.38, p < lt; 0.001) for women. However, there was no marked difference in absolute effect by sex: 4.9% (3.1-6.8) for men vs 4.5% (3.0-6.1) for women. For all analyses traditional logistic regression using the same confounders underestimated the effect in comparison with MSM. Conclusions: Moving below the poverty line increased odds of CMD by 32.7% after accounting for confounding and reverse causality, with a greater relative impact on men. Our causal estimates suggest transition into poverty currently accounts for 10.7% of the burden of CMD in the UK working-age population - 8.9% for women and 13.1% for men. Key messages: Reductions in household income worsen mental health, and traditional analytical approaches may be underestimating this causal relationship. Applying causal methodologies to observational data can provide exposure-outcome estimates less susceptible to common biases, which may be of more use to policymakers.

Item Type:Conference or Workshop Item
Additional Information:Abstract published in European Journal of Public Health, Volume 30, Issue Supplement_5, September 2020, ckaa166.283 [].
Glasgow Author(s) Enlighten ID:Katikireddi, Professor Vittal and Leyland, Professor Alastair and Thomson, Dr Rachel and Pearce, Dr Anna
Authors: Thomson, R. M., Pearce, A., Leyland, A., and Katikireddi, S. V.
College/School:College of Medical Veterinary and Life Sciences > School of Health & Wellbeing > MRC/CSO SPHSU

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