Bipolar disorder in patients with psoriasis and the impact of lithium therapy on psoriasis

There is a significant amount of research examining the link between psoriasis and common mental health disorders; however, studies on less common psychiatric disorders, such as bipolar disorder (BD), remain limited. We conducted a systematic review of studies in the PubMed and Cochrane databases that explored the relationship between BD and psoriasis. In addition, we evaluated the impact of lithium on psoriasis in patients with BD and included a quality assessment of all the studies. This review covers five studies that addressed the connection between psoriasis and psychiatric disorders, three studies on medical conditions in patients with BD, and four studies examining the effects of lithium intake on psoriasis in BD patients. We found substantial evidence supporting a link between psoriasis and BD, suggesting that psoriasis is an independent risk factor for BD. Patients with psoriasis are also more likely to use psychotropic medications. A limited number of studies indicate that lithium therapy may trigger or worsen psoriasis. We also explore the mechanisms of lithium-induced or lithium-aggravated psoriasis, highlighting the intricate interplay between lithium treatment, inositol depletion, and psoriasis in patients with BD. In a placebo-controlled, randomized study, inositol supplementation could mitigate psoriasis in patients taking lithium. Additional research is needed to evaluate the efficacy of inositol supplementation for patients with psoriasis who need to continue lithium treatment for their BD.