People who take their medicine regularly, even dummy (placebo) medicine, have a lower risk of death than those with poor adherence, finds a study in this week's BMJ.
This intriguing finding supports the concept of the "healthy adherer" effect, whereby adherence to drug treatment may be a marker for overall healthy behaviour, say the authors.
They analysed 21 studies involving over 46,000 participants. For those with good adherence to drug therapy or placebo, the risk of mortality was about half that of participants with poor adherence.
Possible reasons for this effect are that participants with good adherence to study drugs (even placebo) may also have good adherence to other healthy behaviours, which could independently affect the risk of mortality, explain the authors. Conversely, participants with poor adherence may have consciously chosen to use a lower dosage or have other conditions, such as depression, that affect adherence.
"Our findings support the tenet that good adherence to drug therapy is associated with positive health outcomes," they write.
"Moreover, the observed association between good adherence to placebo and lower mortality also supports the existence of the healthy adherer effect, whereby adherence to drug therapy may be a surrogate marker for overall healthy behaviour."
In an accompanying commentary, US researcher Betty Chewning suggests that it is quite possible that people who adhere to healthy lifestyles also tend to take care of themselves by greater adherence to prescribed treatments.
She points to research showing that healing may lie not in the treatment but rather in patients' emotional and cognitive processes of "feeling cared for" and "caring for oneself." And she suggests that practice based on these hypotheses "could yield extra value in treatment regimens that patients agree to, believe in, and will sustain over time."