Placebo effect largely ignored in psychological intervention studies
Many brain-training companies tout the scientific backing of their products - the laboratory studies that reveal how their programs improve your brainpower. But according to a new report, most intervention studies like these have a critical flaw: They do not adequately account for the placebo effect.
The new analysis appears in the journal Perspectives on Psychological Science.
The results of psychological interventions, like medical ones, must be compared to improvements in a control condition, said University of Illinois psychology professor Daniel Simons, who co-wrote the article with Walter Boot, Cary Stothart and Cassie Stutts, of Florida State University. In a clinical trial for a new drug, some participants receive a pill with the critical ingredients, and others receive an identical-looking pill that is inert - a placebo. Because participants cannot tell which they received, people in each condition should be equally likely to expect improvements.
In contrast, for most psychology interventions, participants know what’s in their “pill,” Simons said.
“It’s not possible to use a brain-training program for 10 hours without knowing the type of training you received,” he said. “People can form expectations for what will improve based on their experiences with the training tasks, and the existence of differences in expectations between people in treatment and control groups potentially undermines any claim that improvements were due to the treatment itself. Not one of the studies cited by the brain-training companies looks at differing expectations between the groups.”
Merely having an “active control group,” one that does something for the same amount of time as the treatment group, does not protect against the placebo effect, Simons said. A treatment group that completes an intensive memory-training regimen might expect improved performance on other cognitive tasks assessing memory. A control group that does crossword puzzles or watches DVDs for the same amount of time likely won’t expect the same amount of improvement on the same tasks, he said.
What is a placebo?
A placebo (pluh-see-bow) is a substance or other kind of treatment that looks just like a regular treatment or medicine, but it’s not. It’s actually an inactive “look-alike” treatment or substance. This means it’s not a medicine. The person getting a placebo does not know for sure that the treatment is not real. Sometimes the placebo is in the form of a “sugar pill,” but a placebo can also be an injection, a liquid, or even a procedure. It’s designed to look like a real treatment, but doesn’t directly affect the illness.
What is the placebo effect?
Even though they do not act on the disease, placebos seem to affect how people feel (this happens in up to 1 out of 3 patients). A change in a person’s symptoms as a result of getting a placebo is called the placebo effect. Usually the term “placebo effect” speaks to the helpful effects a placebo has in relieving symptoms. This effect usually lasts only a short time. It’s thought to have something to do with the body’s chemical ability to briefly relieve pain or certain other symptoms.
But sometimes the effect goes the other way, and causes unpleasant symptoms or worse. These may include headaches, nervousness, nausea, or constipation, to name a few of the possible “side effects.” The unpleasant effects that happen after getting a placebo are sometimes called the nocebo effect.
Together, these 2 types of outcomes are sometimes called expectation effects. This means that the person taking the placebo may experience something along the lines of what he or she expects to happen. If a person expects to feel better, that may happen. If the person believes that he or she is getting a strong medicine, the placebo may be thought to cause the side effects. The placebo does not cause any of these effects directly. Instead, the person’s belief in or experience of the placebo helps change the symptoms, or change the way the person perceives the symptoms.
Some patients can have the placebo effect without getting a pill, shot, or procedure. Some may just feel better from visiting the doctor or doing something else they believe will help. That type of placebo effect seems most related to the degree of confidence and faith the patient has in the doctor or activity.
“These problems are not limited to brain-training studies,” Simons said. “They hold true for almost all intervention studies.”
To illustrate the pervasiveness of this problem, the researchers examined expectations for improvement in studies of the effect of playing action video games on measures of perception and attention.
“Such studies find greater improvements in performance on attention and perception tasks after training with action video games than after training with non-action games for the same amount of time,” Boot said. “However, even with this sort of active control condition, these interventions still are at risk for differential placebo effects.”
The researchers measured expectations in two survey studies involving 200 participants each. Participants watched either a short video of an action game (“Unreal Tournament”) or one of the games commonly used as controls in these studies (“Tetris” or “The Sims”). They then read descriptions of the cognitive tests used in the studies, watched short videos of the tests, and answered questions about whether they thought their performance on the tests would improve as a result of training on the video game they had viewed.
Animal Placebos
Fact: Placebo Also Occurs Amongst dogs (and other animals)
Pharmaceutical companies employ the same double blind procedures on Dogs when testing K9 medication as they do for human medications. They use two groups - in this particular study all dogs with epilepsy - and give one group the medication and the other group a placebo. It turns out the Placebo phenomenon transcends the human/dog continuum because the placebo group reacted extremely positively to the drugs.
New studies observing siberian hamsters reveal that most animals have something similar to the placebo effect that kicks into gear depending on surroundings and available body energy. When the hamsters are made to believe it is winter time, their immune system goes into a more dormant state to preserve energy. This mechanism helps to explain why we can’t simply will our way toward recovery, but need to take a pill. In essence, we need some sort of external influence to initiate the sequence of events that lead to the placebo effect.
Antidepressant Sham
Fact: Antidepressants Are (basically) A Total Sham
Depression undoubtedly sucks and there is no question about its relation to brain chemistry. However, in recent years doctors have been throwing around prescriptions for depression medications like candy on halloween. This is because they seemingly work, curbing depression for a large percentage of those who take them. However, several high profile studies are showing that placebos basically do the same thing, minus the adverse side effects.
These findings are of course being downplayed by major pharmaceutical companies who would lose out on billions of dollars of profit if antidepressants become less popular. On the other hand, this is very promising news for those who suffer from mental illness because it essentially shows the manner in which these maladies are occurring in our heads and are wholly reversible without the help of nasty chemicals.
The results showed that expectations for improvement were greater for the action-game group than for the control games on exactly the same tests that showed bigger improvements for action-game training in the intervention studies. In fact, the pattern of expected improvements exactly matched actual improvements seen in video game intervention studies, the researchers found.
“If expectations for improvement align perfectly with the actual improvements, then any claim that the treatment was effective is premature,” Simons said. “Researchers must first eliminate differences in expectations across conditions.”
“Even though participants in psychology interventions typically know the nature of their intervention – you can’t play a video game without knowing the game you’re playing - there are steps researchers can take to ensure that the advantages of the treatment group are not due to expectations,” Boot said.
Fact: Placebo Effect Has Become More Powerful Over The Years.
Placebo effect was first noted in the late 1700s, but the true physiological implications weren’t really understood until the 1970s. Still, it seems that the more testing medical experts conduct, the more powerful the placebo effect has become over time. This is largely thought to be a result of our social conditioning; we place a lot of faith in medical professionals. As medical technology improves, mortality decreases and our faith in medicine becomes stronger.
We take comfort in the routine of going to the doctor, being examined, going to the pharmacy and getting pills to take. We expect it to cure us and over time this expectation has become even more pronounced as our faith in science has strengthened. In the middle ages there would have been very little reason to have faith in the medical procedures that killed most people. But today, as medicinal abilities become perpetually more advanced, the impetus to have faith in drugs will continue to grow. With this, the placebo effect will simultaneously grow.
For example, researchers can mislead participants as to the expected benefits of a particular intervention, giving those in the control group higher expectations for improvement than those in the treatment group. Researchers also can assess expectations generated by treatments in a separate sample of participants to ensure that expectations do not differ between intervention and control treatments.
“Although placebo effects can be helpful as well, we need to know what causes improvements in an intervention,” Simons said. “We don’t want to recommend new therapies, change school curricula, or encourage the elderly to buy brain-training games if the benefits are just due to expectations for improvement. Only by using better active controls that equate for expectations can we draw definitive conclusions about the effectiveness of any intervention.”
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Simons is an affiliate of the Beckman Institute for Advanced Science and Technology at Illinois.
Editor’s notes: To reach Walter Boot, call 850-645-8734; email .(JavaScript must be enabled to view this email address).
The paper, “The Pervasive Problem with Placebos in Psychology: Why Active Control Groups are Not Sufficient to Rule out Placebo Effects,” is available from the U. of I. News Bureau.
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Daniel Simons
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217-689-1527
University of Illinois at Urbana-Champaign