aphar

http://www.sciam.com/article.cfm?id=placebo-effect-a-cure-in-the-mind&print=true

Belief is powerful medicine, even if the treatment itself is a sham. New research shows placebos can also benefit patients who do not have faith in them

The latest research has shown that the placebo effect does not always arise from a conscious belief in a drug. Alternatively, it may grow out of subconscious associations between recovery and the experience of being treated, from the pinch of a shot to a doctor’s white coat. Such subliminal conditioning can control bodily processes, including immune responses and the release of hormones. Meanwhile researchers have decoded some of the biology of placebo responses, demonstrating that they stem from active processes in the brain.

In 2003 neuroscientist Fabrizio Benedetti of the University of Turin Medical School in Italy and his team tested the relative influence of expectation and conditioning in 60 volunteers who underwent a procedure that caused severe arm pain. They gave some of the participants a saline injection and told them the shot would intensify their pain; other volunteers were also given the placebo pain promoter but in addition underwent conditioning to decrease pain in which the saline shot was preceded by injections of the nonsteroidal anti-inflammatory drug (NSAID) ketorolac. In both groups pain increased, demonstrating that negative expectation is a powerful nocebo in the case of pain. What is more, anticipating more pain led to increased agony despite conditioning to an analgesic, showing that expectation influences pain more than conditioning does.

On the other hand, suggestion is relatively impotent when it comes to involuntary bodily responses. In another experiment in the same study, Benedetti’s team told participants that a saline shot would alter levels (either up or down, depending on the group) of growth hormone or the stress hormone cortisol. But the suggestions had no effect on either hormone. In contrast, a saline injection did alter hormone concentrations when the researchers conditioned subjects with sumatriptan, a drug that influences their secretion. These placebo-induced biological changes occurred even if the participants were told the saline injection would have an effect opposite to that of sumatriptan. Thus, conditioning can manipulate involuntary physiological processes more than conscious beliefs can.

Expectation and conditioning placebos also work through separate biological mechanisms. In an experiment conducted by Benedetti and Turin neuroscientist Martina Amanzio, volunteers who received a shot of saline touted to be a pain reliever could bear more pain in their arms than they could without the shot. No pain relief was evident, however, when the saline was replaced by naloxone, a substance that blocks the function of the body’s natural painkillers, endogenous opioids. This result suggests that the expectation effect works through the release of these opioids.

Placebo Performance

Despite the proved power of suggestion, investigators have been unable to identify personality traits that increase susceptibility to placebos. Personality, after all, has little effect on subconscious conditioning. For such subliminal responses, presentation matters more than personality does. Giving a medication a popular brand name or prescribing more frequent doses can boost the efficacy of a placebo. Similarly, a physician can maximize a placebo effect by radiating confidence or spending more time with the patient. Such tactics may subconsciously build a patient’s trust in a therapy.

A high price tag on the drug can apparently help, too. In one study, placebos reported to cost $0.10 worked considerably less well in relieving pain than did those priced at $2.50 per pill. Test subjects evidently distrusted the less expensive medication. Patients are also liable to benefit more from placebos that involve elaborate medical procedures than from those requiring simple measures. Thus, the most effective sham treatments may extend beyond dispensing inactive pills to a simulation of a multistep therapeutic regimen.

As evidence of this idea, counseling psychologist Cynthia McRae of the University of Denver and her colleagues reported in 2004 the surprising success of a sham brain surgery in improving the quality of life of patients with advanced Parkinson’s disease. Surgeons performed the sham operation to compare its efficacy with that of implanting human embryonic dopamine neurons into the brains of Parkinson’s patients, who suffer from a lack of dopamine. In McRae’s follow-up study, which assessed the patients’ quality of life up to a year later, the researchers found that the patients who received the sham surgery were doing just as well physically, socially and emotionally as were the patients who had received the new cells. What mattered was not the transplant itself but whether a patient thought he or she had received it.

In recent years extensive research revealing the many medical applications, types and mechanisms of placebo effects has given credence to this once orphaned phenomenon. Doctors are now considering placebo pills and procedures as a way of enhancing the effectiveness of drugs and surgery. Such uses may elicit new controversies and questions such as the use of placebos to boost athletic performance. In the meantime, sophisticated doctors might decide to manipulate the conscious and subconscious mind in ways that could cure—or at least, do no harm.