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Publication - Mrs Carolina Borges

    Assessing causality in the association between attention-deficit/hyperactivity disorder and obesity

    a Mendelian randomization study

    Citation

    Martin-Silva, T, Vaz, J, Hutz, M, Salatino-Oliveira, A, Genro, J, Hartwig, FP, Maia, C, Rohde, L, Borges, C & Tovo-Rodrigues, L, 2019, ‘Assessing causality in the association between attention-deficit/hyperactivity disorder and obesity: a Mendelian randomization study’. International Journal of Obesity.

    Abstract

    Background/Objectives

    Attention-deficit hyperactivity disorder (ADHD), one of the most common neurodevelopmental disorders in childhood and adolescence, is associated with obesity in observational studies. However, it is unclear whether ADHD contributes to, results from or is merely correlated with obesity. This study evaluates the presence and direction of a causal effect between ADHD and obesity.

    Subjects/Methods

    We performed a bidirectional two-sample Mendelian randomization using summary data from consortia of genome-wide association studies to investigate if ADHD (N = 55,374) has a causal effect on body mass index (BMI) in childhood (N = 35,668) and adulthood (N = 322,154–500,000), and vice-versa. The main analysis was performed using the inverse variance weighted (IVW) method. As sensitivity analyses, we used other Mendelian randomization methods that are more robust to horizontal pleiotropy (i.e., MR-Egger, weighted mode, and penalized weighted median estimators), as well as stratified the analysis by the putative mechanisms of genetic instruments (i.e., pathways involved or not in neurological processes).

    Results

    The IVW method indicated a positive causal effect of BMI on ADHD: β = 0.324 (95% CI 0.198 to 0.449, p < 0.001; expressed as change in ln(odds ratio) of ADHD per each additional SD unit of BMI). IVW estimates were directionally consistent with other methods. On the other hand, we did not find consistent evidence for a causal effect of ADHD genetic liability on BMI.

    Conclusions

    The results suggested that higher BMI increases the risk of developing ADHD, but not the other way around.

    Full details in the University publications repository