We need only look to history to understand how race was constructed and how little grounding it ever had in biology. One reason counter-assumptions persist is that racial categories are such looming presences in our social and cultural lives that we can't imagine they don't have a firmer biological basis. This is not to say that group-level differences do not exist—for example, in certain genetic conditions that run in families—and indeed, such research should not be dismissed if it can yield useful insights. But it must also be remembered that where such variations are seen, they are fuzzy and marginal, and cannot be a reliable guide to the treatment of any one patient. Very often, environmental and social factors are at play rather than biological ones. In the case of hypertension, one dominant risk factor is diet, particularly salt consumption. Alongside other known social risk factors such as physical inactivity and obesity, research looking at hypertension in black Americans suggests that there might also be an association with stress, possibly including the stress associated with racial discrimination.