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Original article
Unravelling the interaction between the DRD2 and DRD4 genes, personality traits and concussion risk
  1. Shameemah Abrahams1,2,
  2. Sarah McFie1,
  3. Miguel Lacerda3,
  4. Jon Patricios4,5,6,
  5. Jason Suter7,
  6. Alison V September1,
  7. Michael Posthumus1
  1. 1 Division of Exercise Science and Sports Medicine, Department of Human Biology, Faculty of Health Science, University of Cape Town, Cape Town, South Africa
  2. 2 Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa
  3. 3 Department of Statistical Sciences, Faculty of Science, University of Cape Town, Cape Town, South Africa
  4. 4 Sports Concussion South Africa, Johannesburg, South Africa
  5. 5 Section of Sports Medicine, University of Pretoria, Pretoria, South Africa
  6. 6 Department of Emergency Medicine, University of the Witwatersrand, Johannesburg, South Africa
  7. 7 Cape Sports Medicine, Sports Science Institute, Cape Town, South Africa
  1. Correspondence to Dr Michael Posthumus; mposthumus{at}me.com

Abstract

Background Concussion occurs when biomechanical forces transmitted to the head result in neurological deficits. Personality may affect the balance between safe and dangerous play potentially influencing concussion risk. Dopamine receptor D2 (DRD2) and dopamine receptor D4 (DRD4) genetic polymorphisms were previously associated with personality traits.

Objectives This case–control genetic association study investigated the associations of (1) DRD2 and DRD4 genotypes with concussion susceptibility and personality, (2) personality with concussion susceptibility and (3) the statistical model of genotype, personality and concussion susceptibility.

Methods In total, 138 non-concussed controls and 163 previously concussed cases were recruited from high school (n=135, junior), club and professional rugby teams (n=166, senior). Participants were genotyped for DRD2 rs12364283 (A>G), DRD2 rs1076560 (C>A) and DRD4 rs1800955 (T>C) genetic variants. Statistical analyses including structural equation modelling were performed using the R environment and STATA.

Results The rs1800955 CC genotype (p=0.014) and inferred DRD2 (rs12364283–rs1076560)–DRD4 (rs1800955) A–C–C allele combination (p=0.019) were associated with decreased concussion susceptibility in juniors. The rs1800955 TT and CT genotypes were associated with low reward dependence in juniors (p<0.001) and seniors (p=0.010), respectively. High harm avoidance was associated with decreased concussion susceptibility in juniors (p=0.009) and increased susceptibility in seniors (p=0.001). The model showed that a genetic variant was associated with personality while personality was associated with concussion susceptibility.

Conclusion These findings highlight the linear relationship between genetics, personality and concussion susceptibility. Identifying a genetic profile of ‘high risk’ behaviour, together with the development of personalised behavioural training, can potentially reduce concussion risk.

  • dopamine receptor genes
  • concussion history
  • reward dependence
  • behaviour
  • rugby

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

https://doi.org/10.1136/bmjsem-2018-000465

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    Footnotes

    • Funding This study and authors were funded by the South African National Research Foundation (grant numbers: 90942, 93416, 85534), the Deutscher Akademischer Austauschdienst (DAAD) and the University of Cape Town. Funders had no involvement in the paper.

    • Competing interests None declared.

    • Patient consent for publication Not required.

    • Ethics approval Ethical approval was obtained from the Human Research Ethics Committee of the University of Cape Town.

    • Provenance and peer review Not commissioned; externally peer reviewed.