Amos Hayes, Psychology Undergraduate, University of Portsmouth
In some quarters the claim that psychotherapy is no better than a placebo is considered valid albeit a matter of conjecture and debate with or without clinical research evidence. This review attempts to outline why these claims were made and to balance hearsay against published work on the subject with particular reference in the field of depression.
Early Studies
In 1801, the first results of a placebo controlled experiment were reported by John Haygarth, his conclusions stating that; “the wonderful and powerful influence of the passions of the mind upon the state of the body are too often overlooked in the cure of diseases”. From this point placebos were used in research as a control against any potential cures. The word placebo, however, was only first applied in reference to these experimental controls in 1938, by Diehl, Baker and Cowan. In 1955 Henry K Beecher was one of the first to publish a paper discussing the placebo effect, in his paper, ‘The Powerful Placebo’, he analysed 15 placebo controlled trials and concluded that the placebo effect has a magnitude of 35.2%, these results however have been discounted by Kienle and Kiene (1997). Despite this the paper still had a huge influence on the research to follow, with most research using a similar method of collating and analysing multiple clinical trials. This method of analysing clinical trials has been used to compare the efficacy of psychotherapy to placebo controls, the findings from which, have led to some psychologists (cuijpers et al, 2013) arguing against the efficacy of psychotherapy due to the similarities found between the psychotherapy and a placebo within trials.
This argument can become clearer when compared to the proposed definitions of the placebo effect. Shapiro (1968) first stated that a placebo is: “Any treatment used for its ameliorative effect but that is actually ineffective or not specifically effective for the condition being treated”. Shapiro later developed this definition with Morris in 1978, stating a placebo can be defined as: “Any therapy or component of therapy that is deliberately used for its nonspecific, psychological, or psychophysiological effect”. Both definitions state how a placebo is used for its nonspecific effect however it is Shapiro and Morris’ 1978 definition which links best to psychotherapy. Psychotherapy is a group of therapies aiming to treat psychological disorders, by aiming to change faulty behaviours, thoughts or perceptions (APA 2012) and is being used for its psychological effect, thus linking in to Shapiro and Morris’ 1978 definition. These proposed similarities lead to comparative research between placebos and psychotherapy, especially when treating depression, (Prioleau, Murdock & Brody, 1983; Elkin et al, 1989; Cuijpers et al, 2013) and some of these found similarities in efficacy, leading to the question that is psychotherapy any better than a placebo when treating depression?
Cognitive Models
These claims about psychotherapy’s efficacy compared to a placebo link in to the argument regarding the best treatments for depression, and ultimately what causes depression. If one were to take a stance that depression was purely chemical then they would most likely argue that there is good reason for psychotherapy to be considered similar to a placebo, due to both having psychological and not chemical effects. However if one were to accept the cognitive models for depression then psychotherapy would not fit Shapiro’s 1968 definition of a placebo as it would be considered an effective treatment, due to research findings. Ultimately psychotherapy and drug therapy are used hand in hand when treating depression (UK National Health Service – NHS, 2015).
Although psychotherapy has been proven to be effective while treating depression (Schulberg et al, 2002), research findings have still suggested a similar efficacy to a placebo. Psychologists have thus attempted to explain why similarities are still found; some have pointed out flaws in the research (Kirsch, 2005; Chambless et al 1998), while others have attempted to explain the placebo effect and thus link it into other treatments (Montgomery & Kirsch, 1997). Using these explanations one can argue that although research may have found similarities, this research can be picked apart and that psychotherapy is still effective at treating depression (Schulberg et al, 2002; Bolton et al, 2003) no matter how similar it is to a placebo.
Unpublished Work
An early review which compared psychotherapy and placebo efficacy was Prioleau, Murdock and Brody (1983). They used thirty two studies that they considered to be the most credible portion of a data set produced by Smith, Glass and Miller (1980). The thirty two studies were used to compare the results of the efficacy of the placebo control to that of psychotherapy. From this they found that psychotherapy only had a slightly higher efficacy than a placebo and concluded that there was no clear evidence to suggest the benefits of psychotherapy over a placebo treatment. Similar findings were also documented by Elkin et al (1989). Despite these early findings the field of psychotherapy has still flourished and cemented itself as a key treatment for depression. Further research was carried out and a more recent study found that when compared to psychotherapy a placebo pill was just as effective, however it was found that antidepressant pills were only slightly better than a placebo, thus suggesting that perhaps the placebo effect in this study was greater (Cuijpers et al, 2013). A lot of studies in this area use both published and unpublished studies and Cuijpers et al (2014) did a follow up paper to their one in 2013 and stated that in a lot of unpublished trials have yielded reduced effect sizes when compared to the placebo. Therefore suggesting a reason for the similarity between placebo effectiveness, psychotherapy and anti-depressant medication within Cuijpers 2013 study. Cuijpers et al (2014) thus concluded that due to the issue with unpublished research, psychotherapy cannot be discounted when considering treatments for depression.
Both Cuijpers et al (2013) and Proleau et al (1983) used a pill placebo when evaluating the effectiveness of psychotherapy, however it has been argued that to truly test the effectiveness of psychotherapy, then it should be considered against some sort of psychotherapy placebo (Paul, 1967). A psychological placebo differs from a pill placebo due to it simply not being administered in a pill form; to apply a psychological placebo to Shapiro’s (1968) definition, a psychological placebo is a psychological treatment which is not specifically effective for the condition being treated. This idea of a psychological placebo being used as a control when evaluating psychotherapy has been supported by Chambless et al (1998) as well as the APA (1996), who both argue that to construct lists of empirically supported treatments, psychotherapy can only be considered against psychological placebos. A study to compare a psychological placebo, a pill placebo and psychotherapy was Wampold et al (2005). Wampold et al did find similarities between the effectiveness of a pill placebo and psychotherapy, however psychotherapy did have much higher efficacy than a psychological placebo, thus suggesting that psychotherapy, when compared to a placebo of similar nature, is more effective and thus should not be discounted due to its similarities to a pill placebo.
There are issues with psychological placebo’s and Irving Kirsch (2005) argued that psychotherapy and a psychological placebo are both synonyms and oxymoron’s of each other, as psychotherapies can be considered placebo like as by definition the effects are psychological. Kirsch also claims that it is not possible to produce a psychological placebo without it being considered a psychological treatment, as the placebo would have a psychological, treatment-like effect, thus enforcing the idea that the two are oxymoronic. Kirsch argues that it is, thus, hard to compare psychological placebos and psychotherapy due to their striking similarities. Borkovec and Sibrava (2005) agree with Kirsch and argue that it is hard to investigate the effectiveness of psychotherapy by comparing it to placebos based on the arguments made by Kirsch. They also stated how it is hard to truly measure the effects of psychotherapy compared to a placebo as the results will only ever be qualitative, which is hard to evaluate in a clinical trial environment. They also noted that psychological placebos cannot be administered in a double blind design, which can bring in some issues, as the administer may influence the results, and the participant realise that they are not being treated with psychotherapy.
Expectancy and Conditioning
Some psychologists have attempted to explain the placebo effect through psychological mechanisms. These mechanisms can then be used to explain the research findings that suggest a similarity in effectiveness between a placebo and psychotherapy. Some of the theories which attempt to explain the placebo effect, look into expectancy (Price and Fields, 1997; Kirsch, 1997). Kirsch (1997) based his theory on the research he carried out with Montgomery in 1997. They found that a placebo would appear more effective if an individual’s expectations were manipulated to be higher before the placebo was administered. Thus leading into Kirsch’s theory which suggests that the placebo effect is caused due to the expectancy of being treated. Another theory attempting to explain the placebo effect, relates into the idea of classical conditioning. Ader (1997) and Williamson-Stewart and Podd (2004) argue that humans form a pain relief response towards treatment, through conditioning, and thus when a placebo mocks a treatment our body’s response is to feel better due to how it has been conditioned. Both these theories (expectancy and conditioning) all hold psychological process as central concepts and thus the bridge between psychotherapy (psychological treatments) and a placebo can be narrowed due to the arguable psychological impacts of both.
Although research has found similarities in effectiveness in treating depression, between psychotherapy and a placebo (Prioleau et al, 1997; Cuijpers et al, 2013), there are flaws in the findings and arguments based off of these pieces of research. Initially one can comment on how it is hard to compare psychotherapy with a pill placebo and that to truly be able to evaluate psychotherapy’s efficacy one must compare it to a psychological placebo (Chambless et al, 1998; Paul. G, 1966). This stance was developed by the American Psychological association whom stated that to truly empirically evaluate psychotherapy psychological placebo’s should be used as a control, and evidence did suggest that psychotherapy is more effective than a psychological placebo compared to a pill placebo (Wampold, 2005). The key issue with research in this area is the similarity between psychotherapy and a placebo. Kirsch (2005) argued that psychotherapy and placebos are too similar as they both induce psychological effects, which links in to Shapiro and Morris’ (1978) definition that a placebo is used for its psychological effects. Despite these criticisms, explanations for the findings still had to be considered, and if one were to apply theories of the placebo effect to the research then one would be able to suggest why the effectiveness of the a placebo and psychotherapy were so similar. Both expectancy (Price and Fields, 1997; Kirsch, 1997) and conditioning (Ader, 1997; Williamson-Stewart and Podd, 2004) are theories which rely on a psychological concept as their core and thus may suggest similarities between placebo effectiveness and psychological treatments.
Ultimately this entire argument over the efficacy of psychotherapy compared to a placebo can be bought in to the much larger argument as to the most effective way to treat depression. The NHS suggests that most sufferers of severe depression use a combination therapy of both antidepressants and psychotherapy, and this is seen as the most effective way to treat depression, especially in the long run as it reduces regression. The argument that psychotherapy is no better than a placebo suggests that psychotherapy may not be as effective at treating depression as appears, however research has found psychotherapy to be effective, especially in long term treatment (Schulberg et al, 2002; Bolton et al 2003). This thus suggests that perhaps the effectiveness of a placebo has been underestimated. Research in this area is scarce as many studies that find a high placebo effectiveness are not published. Although Henry K Beecher first noticed the true power of a placebo in 1955, when he published his paper ‘the powerful placebo’ research investigating the true power is rare and more needed to truly understand the similarities in effectiveness found between a placebo and psychotherapy.
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