3 ms·

It's impossible to test "absolute" effects of drugs, so they are always tested in relation to each-other, this makes analysis easy because the only variable tha

by Phemist 11y ago

It's impossible to test "absolute" effects of drugs, so they are always tested in relation to each-other, this makes analysis easy because the only variable that's different is between whether participants are taking the actual drug, or a placebo. What you're suggesting would require testing a placebo in relation to not taking anything, which would introduce a lot more variables, and would make it impossible to do double-blind testing.

corin_ 11y ago
OK so the answer is I don't understand drug testing :) My understanding was: you need the placebo to compare to to counter out the placebo effect (i.e. if you only test "real drug vs. nothing", the real drug might show an improvement purely due to placebo and have no actual effect itself). But introducing more variables... surely there are lots of other variables there regardless? If you ran a test of "placebo vs. nothing" what variables come in that wouldn't be there for "placebo vs. drug"?
- Phemist 11y ago
  First off, the reason double-blind testing is so effective is that it reduces subconscious biases in behaviour. If the person administering drugs knows its a placebo, he/she will consciously, or subconsciously, behave differently. All sorts of unwanted effects come into play, most importantly Observer-expectancy (For a good example, https://en.wikipedia.org/wiki/Clever_Hans https://en.wikipedia.org/wiki/Clever_Hans) Double-blind testing allows one to test the effects of administering anything (the placebo effect), versus the effects of the actual drugs. By administering an inert substance, the baseline placebo effect can be tested, as no actual medicative effects are expected from this inert substance. When testing placebo vs nothing, in the nothing case a lot changes. The participants will no longer be administered anything, the experimenters will be aware of not administering anything, etc. etc. Because so many variables change in such a set-up, you can no longer actually tell which of these variables changing caused the effect and which of them didn't. Thus making any results and conclusion derived from the suspect.
  - austinjp 11y ago
    I'm not entirely sure about that. Some trial designs do indeed have an arm of "no intervention" or "usual care" or "waiting". Sometimes these groups may be given the active therapy after the trial ends, since withholding a potentially effective and efficacious therapy may be considered unethical. There are many trial designs, not all of them are lab-based - - "pragmatic" trials in particular don't tend to follow typical masked, randomised, placebo-controlled designs.

by Phemist 11y ago

corin_ 11y ago

OK so the answer is I don't understand drug testing :) My understanding was: you need the placebo to compare to to counter out the placebo effect (i.e. if you only test "real drug vs. nothing", the real drug might show an improvement purely due to placebo and have no actual effect itself). But introducing more variables... surely there are lots of other variables there regardless? If you ran a test of "placebo vs. nothing" what variables come in that wouldn't be there for "placebo vs. drug"?

Phemist 11y ago
First off, the reason double-blind testing is so effective is that it reduces subconscious biases in behaviour. If the person administering drugs knows its a placebo, he/she will consciously, or subconsciously, behave differently. All sorts of unwanted effects come into play, most importantly Observer-expectancy (For a good example, https://en.wikipedia.org/wiki/Clever_Hans https://en.wikipedia.org/wiki/Clever_Hans) Double-blind testing allows one to test the effects of administering anything (the placebo effect), versus the effects of the actual drugs. By administering an inert substance, the baseline placebo effect can be tested, as no actual medicative effects are expected from this inert substance. When testing placebo vs nothing, in the nothing case a lot changes. The participants will no longer be administered anything, the experimenters will be aware of not administering anything, etc. etc. Because so many variables change in such a set-up, you can no longer actually tell which of these variables changing caused the effect and which of them didn't. Thus making any results and conclusion derived from the suspect.
- austinjp 11y ago
  I'm not entirely sure about that. Some trial designs do indeed have an arm of "no intervention" or "usual care" or "waiting". Sometimes these groups may be given the active therapy after the trial ends, since withholding a potentially effective and efficacious therapy may be considered unethical. There are many trial designs, not all of them are lab-based - - "pragmatic" trials in particular don't tend to follow typical masked, randomised, placebo-controlled designs.