Psoriasis is a chronic, inflammatory skin disease that is estimated to affect between 0.6% and 4.8% of the population. Lithium - which is used to treat bipolar disorder - is often linked to psoriasis and a study by researchers from Switzerland (using data from the U.K.) of 73,404 people found that long-term lithium use was associated with a small rise in the risk of psoriasis. The use of atypical antipsychotics, mainly olanzapine, was associated with a reduced risk of the skin condition.
Brauchli, Yolanda B. ... [et al] - Lithium, antipsychotics, and risk of psoriasis Journal of Clinical Psychopharmacology April 2009, 29(2), 134-140