Abstract: This update added 48 trials and provided evidence on 7 new active treatments. In total, the review included 177 randomised controlled trials, with 34,808 participants, including 26 trials of scalp psoriasis and 6 trials of inverse psoriasis, facial psoriasis, or both. The number of included studies counted by Review Manager (RevMan) is higher than these figures (190) because we entered each study reporting a placebo and an active comparison into the 'Characteristics of included studies' table as 2 studies. When used on the body, most vitamin D analogues were significantly more effective than placebo, with the standardised mean difference (SMD) ranging from -0.67 (95% CI -1.04 to -0.30; 1 study, 119 participants) for twice-daily becocalcidiol to SMD -1.66 (95% CI -2.66 to -0.67; 1 study, 11 participants) for once-daily paricalcitol. On a 6-point global improvement scale, these effects translate into 0.8 and 1.9 points, respectively. Most corticosteroids also performed better than placebo; potent corticosteroids (SMD -0.89; 95% CI -1.06 to -0.72; I² statistic = 65.1%; 14 studies, 2011 participants) had smaller benefits than very potent corticosteroids (SMD -1.56; 95% CI -1.87 to -1.26); I² statistic = 81.7%; 10 studies, 1264 participants). On a 6-point improvement scale, these benefits equate to 1.0 and 1.8 points, respectively. Dithranol, combined treatment with vitamin D/corticosteroid, and tazarotene all performed significantly better than placebo. Head-to-head comparisons of vitamin D for psoriasis of the body against potent or very potent corticosteroids had mixed findings. For both body and scalp psoriasis, combined treatment with vitamin D and corticosteroid performed significantly better than vitamin D alone or corticosteroid alone. Vitamin D generally performed better than coal tar, but findings relative to dithranol were mixed. When applied to psoriasis of the scalp, vitamin D was significantly less effective than both potent corticosteroids and very potent corticosteroids. Indirect evidence from placebo-controlled trials supported these findings. For both body and scalp psoriasis, potent corticosteroids were less likely than vitamin D to cause local adverse events, such as burning or irritation. Combined treatment with vitamin D/corticosteroid on either the body or the scalp was tolerated as well as potent corticosteroids, and significantly better than vitamin D alone. Only 25 trials assessed clinical cutaneous dermal atrophy; few cases were detected, but trials reported insufficient information to determine whether assessment methods were robust. Clinical measurements of dermal atrophy are insensitive and detect only the most severe cases. No comparison of topical agents found a significant difference in systemic adverse effects. Corticosteroids perform at least as well as vitamin D analogues, and they are associated with a lower incidence of local adverse events. However, for people with chronic plaque psoriasis receiving long-term treatment with corticosteroids, there remains a lack of evidence about the risk of skin dermal atrophy. Further research is required to inform long-term maintenance treatment and provide appropriate safety data.

Plain-language summary: The evidence was based on 177 studies, which, in total, included 34,808 people. Studies were typically about 7 weeks' long, but this ranged from 1 week to 52 weeks. Vitamin D products were found to work better than placebo (the base cream or ointment). Potent topical corticosteroids (strong, e.g. betamethasone dipropionate) and very potent (very strong, e.g. clobetasol propionate) topical corticosteroids were also effective. Some studies compared vitamin D products directly with potent or very potent corticosteroids. These products had similar effects when applied to the body, but corticosteroids worked better than vitamin D for scalp psoriasis. Treatment that combined vitamin D with a corticosteroid was more effective than vitamin D alone and more effective than the topical corticosteroid alone. Vitamin D products generally performed better than coal tar, but studies found conflicting results when comparing vitamin D with dithranol. Whether applied to the body or to the scalp, potent corticosteroids were less likely than vitamin D to cause 'local adverse events', such as skin irritation or burning, and people were therefore more likely to stop using vitamin D products. When studies examined whether topical treatments had effects within the body ('systemic adverse events'), we found no difference between placebo and any other treatment. However, this may be because many trials did not properly assess systemic adverse events, rather than because there really was no difference. More long-term studies would help doctors and people with psoriasis decide on the best way to treat this chronic condition.