Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
Maintenance of remission
RCT Crossover design 4-armed trial	1005 people with psoriasis that had been cleared by PUVA, 831 people with plaque psoriasis, 122 people with guttate psoriasis, 25 people with erythrodermic psoriasis	Proportion of people who relapsed 18 months 27% with treatment once weekly 30% with treatment every 2 weeks 34% with treatment every 3 weeks 62% with no treatment Absolute numbers not reported	P <0.05 for all PUVA regimens combined versus no treatment	Effect size not calculated	PUVA