Double Blind studies: Is it really flawless testing?

Posted on: March 11, 2012

A ‘double blind’ is a term used to describe a decision process whereby parties involved avoid knowing crucialinformation to avoid generating biased results. (Sampson, 2007)  For example, a drug researcher may give participants a set of tablets hidden in foil casing; one set of a certain colour will have a real chemical drug, and the other foiled set will be a placebo.  Neither the drug researcher nor participants will know whether or not the medication was the real thing until the experiment has been completed. (Margraf, 1991)
Double blind testing is a common process for testing placebo effects with drugs.  A placebo effect describes the phoenomenon in which self-soothing occurs; symptoms can be aleviated by an otherwise ineffective treatment; a psychosomatic self-assurance process.  This placebo effect is a common phoenomenon amongst many drug trials.

Petracca et. al (1996) created a double blind study to test the effects of anti-depressant drugs on patients with Alzheimers who were suffering with depression.  21 Alz patients recieved a 6-week treatment; the results showed a dramatic increase in all participants who had recieved the placebo and the anti-depressant drugs.  However, Patrecca claimed that the placebo patients began to show depression symptoms during the washout period, slowly worsening over time until their moods were the same as before, but the anti-depressant candidates did not suffer during the washout period and instead maintained their moods.

But can we say that this study is flawless?

The main advantages of a double-blind study of rely on its confidence.  If neither the researcher nor the participant knows the effect of their drug then this prevents bias from both the researcher and participant; whether the decision is made consciously or subsconsciously.  But Liebert (2010) believes that many skeptics still see double-blind studies as near-to-flawless and this it has proven a problem in some analysing of studies.

Margraf, 1991 believes the main issue of double-blind studies is that they can be prone to fraud; it is possible for researchers to fabricate data without easily being caught. In these sorts of cases, only further replication of the test and a wider range of studies can detect any fraud.

False positives and false negatives can also have a harmful effect on the studies; if results are not given out (which they are often not with double blind trials) a false score can go a miss.  This is known as publication bias. (Matthews et. al. 1991)

In conclusion, double-blind testing is not flawless, but it does have it’s advantages!  If all results were published from every study, it would avoid publication bias as well as allow for further interpretation and finding fraud within studies. The moral of the story is: don’t be skeptical about a study just because it’s double-blind; it’s not always flawless!



[all references are linked]


7 Responses to "Double Blind studies: Is it really flawless testing?"

I’ll be honest, before reading this I was genuinely unsure what a double blind study was so thank you for clearing that up! I can understand the benefits of this type of study, however i’ve got to raise some ethical implications. Take Petracca’s study that you mentioned earlier. I understand that the experiment was to test the effects of the anti-depression medication on people with Alzheimers, but is it really ethical to with-hold potential treatment to other patients? Surely as clinicians, it’s their duty to provide the up-most care and treatment to each patient and help in whatever ways they can. It must be considered any potential harm to the patients with Alzheimers that didn’t receive treatment, and their feelings afterwards. Just with double blind measures, the intentions were purely good, however both double blind studies and the example above have drawbacks and problems.

I think this is a very intresting issue you’ve written about and not one I had ever thought about. I guess my biggest issue of double blind experiemnts would have to be that there is a more chance of error because there is less stages where error could be discovered as people do not know what is ment to be correct.

I mean outliers in double blind experiemnts must be more of an issue. Is it a genuine outlier where someone has just responded differntly to the medication/placebo and thus could require future research or was it becasue there wa sa mix-up. How can you be sure?

Yet these are very important types of experiments and they have a real benefit to psychology and other fields I just think when reading and evaluating these types of studies you need to consider that fraud and more error could be issues and this needs to be weighed up when viewing the results and conclusions.

i would argue that double blind studies are not flawless due to experimental errors, however as long as researchers can be held to the code of ethics placed on all us psychologists there is a high flawlessness rate for double blind studies

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