I do understand about the placebo effect. I studied Pschology back in the dark ages and we always had 'control' groups. It just seemed a bit odd to do it in this case because the AD sufferers won't know if they are better or not and it will be down to the carers to evaluate the results - and that might be down to subjective opinions in the long run.
I always remember one test we read about which was a caution about forming erroneous conclusions. There were 14 trainee psychologists who each were given a fly in a box and were told to command it to walk at hourly intervals. Each day they had to cut off one leg from the fly and record the effects. At the end of the test their conclusions were that 'if you cut all the legs off a fly, it becomes deaf'.