Duration
Placebo effects can last for a long time: over 8 weeks for panic disorder,6 months for angina pectoris, and two and half years for rheumatoid arthritis. Placebo effects after verbal suggestion for mild pain can be robust and still exist after being repeated 10 times even if they have no actual pharmacological pain killing action
Clinical significance
Hróbjartsson and Peter Gøtzsche published a study in 2001 and a follow-up study in 2004 questioning the nature of the placebo effect. The studies were performed as two meta-analyses involving all 156 published clinical trials in which an experimental drug or treatment protocol was compared to a placebo group and an untreated group, and specifically asked whether the placebo group improved compared to the untreated group. Hróbjartsson and Gøtzsche found that in studies with a binary outcome, meaning patients were classified as improved or not improved, the placebo group had no statistically significant improvement over the no-treatment group. Similarly, there was no significant placebo effect in studies in which objective outcomes (such as blood pressure) were measured by an independent observer. The placebo effect could only be documented in studies in which the outcomes (improvement or failure to improve) were reported by the subjects themselves. The authors concluded that the placebo effect does not have "powerful clinical effects," (''objective'' effects) and that patient-reported improvements (''subjective'' effects) in pain were small and could not be clearly distinguished from reporting bias. Other researchers have argued that the placebo effects for objective symptom measures are comparable to placebo effects for subjective ones and that the placebo effect can exceed the effect of the active treatment by 20% for disorders amenable to the placebo effect.Hróbjartsson and Gøtzsche's conclusion has been criticised on several grounds. Their meta-analysis covered studies into a highly mixed group of conditions: the placebo effect does occur with peripheral disease processes (such as Hypertension, asthma, prostatic hyperplasia, anal fissure, bronchitis) though not for processes reflecting physical disease (such as venous leg ulcers, Crohn’s disease, urinary tract infection, and chronic heart failure). Placebos also do not work as strongly in clinical trials because the subjects do not know whether they might be getting a real treatment or a sham one. Where studies are made of placebos in which people think they are receiving actual treatment (rather than merely its possibility) the placebo effect has been observed. Other writers have argued that the placebo effect can be reliably demonstrated under appropriate conditions.
Negative effects
Similar to the placebo effect, inert substances have the potential to cause negative effects via the "nocebo effect" (Latin ''nocebo'' = "I will harm"). In this effect, giving an inert substance has negative consequences.Another negative consequence is that placebos can cause side-effects associated with real treatment. One example of this is with those that have already taken an opiate, can then show respiratory depression when given it again in the form of a placebo.
Withdrawal symptoms can also occur after placebo treatment. This was found, for example, after the discontinuation of the Women's Health Initiative study of hormone replacement therapy for menopause. Women had been on placebo for an average of 5.7 years. Moderate or severe withdrawal symptoms were reported by 40.5% of those on placebo compared to 63.3% of those on hormone replacement.
Doctor-patient relationship
A study of Danish general practitioners found that 48% had prescribed a placebo at least 10 times in the past year. The most frequently prescribed placebos were antibiotics for viral infections, and vitamins for fatigue. Specialists and hospital-based physicians reported much lower rates of placebo use. A 2004 study in the British Medical Journal of physicians in Israel found that 60% used placebos in their medical practice, most commonly to "fend off" requests for unjustified medications or to calm a patient. The accompanying editorial concluded, "We cannot afford to dispense with any treatment that works, even if we are not certain how it does." Other researches have argued that open provision of placebos for treating ADHD in children can be effective in maintaining ADHD children on lower stimulant doses in the short term.Critics of the practice responded that it is unethical to prescribe treatments that don't work, and that telling a patient that a placebo is a real medication is deceptive and harms the doctor-patient relationship in the long run. Critics also argued that using placebos can delay the proper diagnosis and treatment of serious medical conditions.
The following impracticalities exist with placebos (see the BMJ posted responses to Spiegel's editorial [http://bmj.bmjjournals.com/cgi/content/full/329/7472/927 rapid response online section]).
* Roughly only 30% of the population seems susceptible to placebo effects, and it is not possible to determine ahead of time whether a placebo will work or not.
* All placebo effects eventually wear off, thus making the placebo effect impractical for long term or chronic medical matters.
* Patients rightfully want immediate relief or improvement from their illness or symptoms. A non-placebo can often provide that, while a placebo might not.
* Legitimate doctors and pharmacists could open themselves up to charges of fraud since sugar pills would cost pennies or cents for a bottle, but the price for a "real" medication would have to be charged to avoid making the patient suspicious.
About 25% of physicians in both the Danish and Israeli studies used placebos as a diagnostic tool to determine if a patient's symptoms were real, or if the patient was malingering. Both the critics and defenders of the medical use of placebos agreed that this was unethical. The British Medical Journal editorial said, "That a patient gets pain relief from a placebo does not imply that the pain is not real or organic in origin...the use of the placebo for 'diagnosis' of whether or not pain is real is misguided."
The placebo administration may prove to be a useful treatment in some specific cases where recommended drugs can not be used. For example, burn patients who are experiencing respiratory problems cannot often be prescribed opioid (morphine) or opioid derivatives (pethidine), as these can cause further respiratory depression. In such cases placebo injections (normal saline, etc.) are of use in providing real pain relief to burn patients if those not in delirium are told they are being given a powerful dose of painkiller.
Referring specifically to homeopathy, the House of Commons of the United Kingdom Science and Technology Committee has stated:
Adapted from the Wikipedia article Placebo, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki
