Posted by ed_uk2010 on February 16, 2015, at 7:06:05
In reply to Re: placebo, posted by alexandra_k on February 15, 2015, at 21:14:47
What makes a placebo more or less effective in psychiatric drug trials? Quite a lot of things actually:
Placebo injections have particularly marked effects. There is an expectation that injections are powerful.
Branded placebos are more effective than generic placebo tablets. Perception *is* important.
Coloured capsules are more effective that little white tablets.
In serious illness, any placebo responses may be short-lived.
Placebo response is high when recruiting pts with mild-moderate depression. Spontaneous remission is frequent is this group.
Placebo response is high is trials where a lot of contact with services is provided. The more care and visits provided, the higher the placebo effect.
Placebo response is higher in trials where there is the knowledge that most patients are receiving the active drug and a smaller proportion are receiving placebo. Again, perception is important.
Placebos which cause side effects may be more effective than true placebos. For example, if a non-psych drug which causes dry mouth is chosen instead of an inactive placebo, pts will perceive that they are definitely on an active drug, and will respond better.
Two different placebos in combination can be better than one.
People report side effects with placebos. Several different mechanisms may operate here: the tendency to attribute all symptoms which occur when taking a med to that med - even when actually unrelated, the expectation of certain symptoms will produce them 'this drug will cause nausea = pt experiences nausea', and possibly anxiety-type symptoms due to fear of medication.
Active drugs may appear to be effective in trials entirely due to side effects. For example, a drug which sedates may improve depression rating scales entirely through increased sleep, even in the absence of mood improvement.
There is a tendency for most of those recruited into trials to improve. This is because pts are often included at the point of acute illness, from which some improvement is likely to occur over time, even without treatment. This is true even in severe depression, due to fluctuations in severity over time. Regression towards the mean operates here.
poster:ed_uk2010
thread:1076696
URL: http://www.dr-bob.org/babble/20150129/msgs/1076727.html