NHS Choices state, "Psoriasis occurs when skin cells are replaced more quickly than usual. It's not known exactly why this happens, but research suggests it's caused by a problem with the immune system."
30 November 2016 - note
A 2016 study indicates that one of the immune system messengers, interleukin IL-12, neutralised by ustekinumab, the antibody currently used to treat psoriasis, may actually be helpful in battling the disease.
23 December 2016 - note
A 2016 study indicates that, “weight loss has a significant and prolonged positive impact on psoriasis symptoms and quality of life.”