It also showed a mean maintenance of remission from 38 to 54 weeks compared with 21 weeks for patients who received placebo treatment.
Overall, 92 clusters were assigned vitamin A and 93 placebo treatment.
The others took a placebo treatment containing no cortisone.
A variety of placebo treatments may be used to treat susto.
For comparison, some patients received a placebo treatment during which the same procedure was performed but no shock waves were delivered.
The other group got a placebo treatment that lacked any drug.
Notably in psychological impotence, there is a strong response to placebo treatment.
Most patients also received a placebo treatment during the study, an injection of saline solution, and showed no improvement.
Experts estimate that 30 percent of all patients getting placebo treatment today improve.
Healing rates varied between the studies, but were consistently lower with placebo treatment.
