Is handedness associated with health outcomes for people who inject illicit drugs?

Approximately 10% of the global population is left-handed. Much research has been directed at handedness and health, with reports of left-handers suffering higher rates of numerous health conditions, accidents, injuries and ultimately, significantly reduced lifespans. Most previous research focused on 'well' or general-population samples; no previous investigations of the effects of handedness on injecting drug users' (IDUs) health are known. Aim: To investigate associations between handedness and health outcomes among IDUs-a marginalized population subgroup with significantly worse health than average. Methods: A total of 346 self-identified left- (9.5%) or right-handed current IDUs were recruited in the Australian states of Queensland, New South Wales and Victoria in late 2006 and interviewed about their health and behaviour. Findings: Many socio-demographic, health status and injury occurrence variables were evaluated univariately, but only two were significantly associated with handedness. Left-handers were significantly less likely to report recent scarring or bruising, and significantly more likely to report accidentally penetrating an artery; these variables were also significantly and independently associated (negatively and positively, respectively) with handedness in binary logistic regression. Conclusions: The lack of biological plausibility of the aforementioned variables' associations with handedness, and the contradiction in their directions of association, suggest that left-handedness among IDUs is not associated with significantly worse health outcomes.