A statistical association between two things does not necessarily prove that one thing causes another to occur, but Health News Review saw that principle violated several times in news coverage of several different studies regarding coffee and sleep.

An editorial accompanying the published results of the studies in the Annals stated that the protective qualities of coffee was “biologically plausible” but “the association of coffee intake with mortality, however, was modest and sensitive to confounding.” In other words, other things may account for the statistical association.  Cause and effect was not established.