Life span may be as wide as your smile

LA Times article "Life span may be as wide as your smile" (March 29th, 2010) makes the causal connection between smiling and longevity, among other things. Unfortunately the article doesn't note the fact that causality can run both ways, and giving people encouragement that smiling more will improve their lives may be quite misleading.

People who smile a lot are usually happier, have more stable personalities, more stable marriages, better cognitive skills and better interpersonal skills, according to research. Science has just uncovered another benefit of a happy face. People who have big smiles live longer.

Maybe being happy, having a more stable personality, having a more stable marriage, and better cognitive and interpersonal skills causes one to smile more. When we see a positive correlation between smiling and other measures of happiness, we should be careful not to infer that smiling more will cause improvements in other areas of our lives without evidence that this is the case. Science has not necessarily uncovered the benefit of having a happy face--people are likely happy for a reason.