Psoriasis causes inflammation and an increased production of skin cells. Rather than being replaced every 3-4 weeks, skin cells are replenished in 3-7 days, causing characteristic plaques often found on the knees, elbows, scalp and lower back (although they can appear anywhere on the body).
This is a companion discussion topic for the original article at https://patient.info/news-and-features/psoriasis-and-depression