"To conduct the study, researchers recruited 100 children with upper-respiratory-tract infections who had been coughing for an average of more than three days.Someone needs to study the placebo effect of mothers being bombarded with commercials about how 'proper care' of a child includes lots of expensive medication.
The children were given one of three treatments 30 minutes before bedtime: a cough syrup containing dextromethorphan, a cough syrup containing diphenhydramine or a placebo syrup.
Children in all three groups showed a dramatic reduction in cough frequency, but those taking the placebo -- essentially flavored water -- had the best results. On four other measures, the three treatments had virtually identical outcomes."
File this under, "not likely to be featured in any media that gets advertising money for cough suppresants".