Adherence to treatment and health outcomes.

Adherence (or compliance) is the extent to which a person's behavior coincides with medical or health advice. Recent evidence indicates that patients who adhere to treatment, even when that treatment is a placebo, have better health outcomes than poorly adherent patients. Based on this evidence, we now believe that the outcomes of treatment are not solely attributable to the specific action of a drug, but may also depend on other nonspecific therapeutic effects. We consider the implications of these findings for the design and interpretation of clinical research as well as for the care of patients.