Multi–Polygenic Score Approach to Identifying Individual Vulnerabilities Associated With the Risk of Exposure to Bullying
Authors: Tabea Schoeler, Shing Wan Choi, Frank Dudbridge, Jessie Baldwin, Lauren Duncan, Charlotte M. Cecil, Esther Walton, Essi Viding, Eamon McCrory, Jean-Baptiste Pingault
Journal: JAMA Psychiatry (2019)

<h3>Importance</h3> Exposure to bullying is a prevalent experience with adverse consequences throughout the life span. Individual vulnerabilities and traits, such as preexisting mental health problems, may be associated with increased likelihood of experiencing bullying. Identifying such individual vulnerabilities and traits is essential for a better understanding of the etiology of exposure to bullying and for tailoring effective prevention. <h3>Objective</h3> To identify individual vulnerabilities and traits associated with exposure to bullying in childhood and adolescence. <h3>Design, Setting, and Participants</h3> For this study, data were drawn from the Avon Longitudinal Study of Parents and Children (ALSPAC), a population-based birth cohort study. The initial ALSPAC sample consisted of 14 062 children born to women residing in Avon, United Kingdom, with an expected date of delivery between April 1, 1991, and December 31, 1992. Collection of the ALSPAC data began in September 6, 1990, and the last follow-up assessment of exposure to bullying was conducted when participants were 13 years of age. Data analysis was conducted from November 1, 2017, to January 1, 2019. <h3>Exposures</h3> The polygenic score approach was used to derive genetic proxies that indexed vulnerabilities and traits. A total of 35 polygenic scores were computed for a range of mental health vulnerabilities (eg, depression) and traits related to cognition (eg, intelligence), personality (eg, neuroticism), and physical measures (eg, body mass index), as well as negative controls (eg, osteoporosis). <h3>Main Outcomes and Measures</h3> Single and multi–polygenic score regression models were fitted to test the association between indexed traits and exposure to bullying. Children completed the Bullying and Friendship Interview Schedule at the ages of 8, 10, and 13 years. A mean score of exposure to bullying across ages was used as the main outcome. <h3>Results</h3> A total of 5028 genotyped individuals (2481 boys and 2547 girls) with data on exposure to bullying were included. Among the 35 initially included polygenic scores, 11 were independently associated with exposure to bullying; no significant association was detected for the 24 remaining scores. In multivariable analyses, 5 polygenic scores were associated with exposure to bullying; the largest associations were present for genetic risk relating to mental health vulnerabilities, including diagnosis of depression (standardized<i>b</i> = 0.065; 95% CI, 0.035-0.095) and attention-deficit/hyperactivity disorder (standardized<i>b</i> = 0.063; 95% CI, 0.035-0.091), followed by risk taking (standardized<i>b</i> = 0.041; 95% CI, 0.013-0.069), body mass index (standardized<i>b</i> = 0.036; 95% CI, 0.008-0.064), and intelligence (standardized<i>b</i> = −0.031; 95% CI, −0.059 to 0.003). <h3>Conclusion and Relevance</h3> Using the multi–polygenic score approach, the findings implicate preexisting mental health vulnerabilities as risk factors for exposure to bullying. A mechanistic understanding of how these vulnerabilities link to exposure of bullying is important to inform prevention strategies.