“We are not saying (anti-depression medication) doesn’t work. But the studies that have been done are often of poor quality and it’s therefore difficult to say anything about the effect of antidepressants,” said Asger Sand Paludan-Müller, a PhD student and one of the co-authors of the analysis, as cited by Videnskab.
Previous studies show that the medication is effective but don’t really quantify exactly how much more effective they are than a placebo or alternative treatments. In their recent meta analysis, the Danish researchers highlight pervasive positive selection bias, inadequate reporting of side effects as well as systematic distortion of results in up to 79 percent of the studies analyzed.
“Our argument here is that the uncertainty is so great that we think we should be saying that we don’t actually know for sure.”
In many cases within the meta analysis, previous researchers had stated a number of goals prior to conducting their studies but would then omit negative results and only focus on the goals achieved without mentioning where there were shortcomings, greatly inflating the apparent effectiveness of a given medication.
There were also repeated failures in double-blind tests, generally considered the highest standard of medical research, as both patients and doctors could quickly tell whether a placebo had been administered or not due to the appearance of side effects.