Harriet Hall on Kirsch and Efficacy of Antidepressants

In a previous article entitled Why Jerry Coyne is Wrong about Medical Psychiatry, I strongly scolded Dr. Coyne for naively embracing anti-psychiatry lunacy, making basic scientific errors and often using the exact same pseudoskeptical and pseudoscientific tactics he rejected in other areas, such as creationism and anti-vaccination.

Now, Dr. Harriet Hall over at the Science-Based Medicine blog, has taken on Kirsch conclusions regarding the efficacy of antidepressants in an entry called Antidepressants and Effect Size. In it, Dr. Hall explains that:

  • The effect size of all drugs tested where, compared with placebo, positive.
  • None of the calculated confidence intervals overlapped zero, meaning that it is very unlikely that antidepressants tested and placebo are no different in efficacy.
  • Kirsch made an unfortunate interpretation of clinical significance, concluding that because the effect size was under the arbitrarily selected cut-off value by NICE (National Institutes for Clinical Excellence) of 0.5, Kirsch concluded that there was little or no clinical significance. While it is true that a glass that is 1/3 full is not 1/2 full, a 1/3 glass is not empty. NICE no longer uses this 0.5 effect size cut-off.
  • If Kirsch’s interpretation was reasonable, we would have to reject psychotherapy as a treatment as well antidepressants, because psychotherapy has an even lower effect size.

Dr. Hall goes on to soberly note that:

Once more, science fails to give us the black-and-white answers we crave. And once again we are reminded that we can’t rely on the media for accurate, nuanced information about medical science.

A wise message worthy of serious consideration.

References and Further Reading:

Hall, Harriet (2011). Antidepressants and Effect Size. Science-Based Medicine. http://www.sciencebasedmedicine.org/index.php/antidepressants-and-effect-size/. Accessed 2011-07-19.

Hall, Harriet (2009). Psychiatry-Bashing. Science-Based Medicine. http://www.sciencebasedmedicine.org/index.php/psychiatry-bashing/. Accessed 2010-06-26.

Tuteur, Amy Tuteur. (2010). Study shows antidepressants useless for mild to moderate depression? Not exactly. Science-Based Medicine. http://www.sciencebasedmedicine.org/index.php/study-shows-antidepressants-useless-for-mild-to-moderate-depression-not-exactly/. Accessed 2010-06-26.

Emil Karlsson

Debunker of pseudoscience.

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