Suicide and depression in former contact sports participants: population-based cohort study, systematic review, and meta-analysis
Authors: Batty G. David , Frank Philipp , Kujala Urho M. , Sarna Seppo J. , Kaprio Jaakko 
Published: November 2022

SummaryBackgroundTraumatic brain injury is associated with the future risk of depression and suicide, and this raises the possibility that former participants in sports characterised by low intensity repetitive head impact may also subsequently experience an increased burden of these mental health outcomes. Using new data from a cohort study integrated into a meta-analysis of the current evidence, we compared the occurrence of depression and suicide in former contact sports athletes against general population controls.MethodsThe cohort study comprised 2004 retired male athletes who had competed internationally on an amateur basis for Finland between 1920 and 1965, and 1385 age-equivalent male general population controls. Former contact sports participants were drawn from soccer, boxing, or Olympic-style (non-professional) wrestling. During follow-up, cases of major depressive disorder and suicide were captured via linkage to mortality and hospitalisation registries. In a PROSPERO-registered (CRD42022352780) systematic review, we searched PubMed and Embase from their inception to October 31 2022 for reports of cohort studies of contact sports participation and later risk of depression and suicide that were published in English and reported standard estimates of association and variance. Study-specific estimates were aggregated using random-effect meta-analysis. The Newcastle-Ottawa Scale was used to appraise the quality of each study.FindingsIn analyses of the Finnish cohort data, up to 45 years of health surveillance gave rise to 131 hospitalisations for major depressive disorder and 61 suicides. In survival analyses (hazard ratio [95% confidence interval]) adjusted for age and socioeconomic status, former boxers (depression: 1.43 [0.73, 2.78]; suicide: 1.75 [0.64, 4.38]), wrestlers (depression: 0.94 [0.44, 2.00]; suicide: 1.60 [0.64, 3.99]), and soccer players (depression: 0.62 [0.26, 1.48]); suicide: 0.50 [0.11, 2.16]) did not have statistically significantly different rates of major depressive disorder or suicide relative to general population controls. The systematic review identified 463 potentially eligible published articles, of which 7 met inclusion criteria. All studies sampled men and 3 were evaluated as being of high quality. After aggregating results from these retrieved studies with new data from the cohort study, we found that retired soccer players appeared to have a somewhat lower risk of depression (summary risk ratio: 0.71 [95% 0.54, 0.93]) relative to general population controls, while the rate of suicide was essentially the same (0.70 [0.40, 1.23]). Past participation in American football was associated with some protection against suicide (0.58 [0.43, 0.80]) but there were insufficient studies of depression for aggregation. All studies showed directionally consistent relationships and there was no indication of inter-study heterogeneity (I2=0%).InterpretationBased on a small cluster of studies exclusively comprising men, retired soccer players had a lower rate of later depression, and former American football players had a lower risk of suicide. Whether these findings are generalisable to women requires testing.FundingNone.Research in contextEvidence before this studyA series of cohort studies suggest that brain injury serious enough to necessitate hospitalisation is associated with elevated rates of later depression and suicide. This raises the possibility that former participants in sports characterised by low intensity repetitive head impact, who have an increased risk of other mental health disorders in later life such as dementia, may also experience an increased burden of depression and suicide. Searching PubMed and Embase using terms for specific contact sports (e.g., ‘boxing’, ‘martial’, ‘wrestling’, ‘football’, ‘soccer’, ‘hockey’, ‘rugby’), depression and suicide (e.g., depression, dysthymic; suicide) revealed relevant studies in former athletes from American football, soccer, and rugby union but no evidence for boxing, wrestling, or other contact sports. Overall, there was a suggestion of mixed results and an absence of a quantitative synthesis of findings for depression.Added value of this studyIn the first cohort study to simultaneously examine the risk of depression and suicide across multiple contact sports, there was no convincing evidence that retired boxers, wrestlers, or soccer player had a different rate of these health outcomes than the general population. After incorporating these new results into a meta-analysis, former soccer players had a lower risk of depression but there was no clear link with suicide. Retired American footballers appeared to experience lower suicide rates at follow-up.Implications of all the available evidenceCounter to the apparent impact of traumatic brain injury, a background in contact sports was not associated with elevated rates of depression or suicide. Indeed, former soccer athletes (depression) and American football players (suicide) seemed to experience some protection against these health outcomes. The existing evidence base is, however, hampered by an absence of studies of women, and is modest in scale and narrow in scope, currently not including several popular contact sports.