Researchers recently reviewed the performance of these two psoriasis treatments. In all, 177 trials were included in the researchers’ study. They found that vitamin D and corticosteroids worked better as a combined treatment than either one treatment on its own. The researchers also noted that vitamin D was significantly less effective than potent corticosteroids when used to treat scalp psoriasis. However, they cautioned that most of the trials failed to report if long-term use of corticosteroids increases the risk for permanent skin dermal atrophy—a condition where the skin thins.