The primary aim of this meta-analysis was to determine the relationship between anti-TNF α treatment versus no anti-TNF α treatment (or treatment with DMARDs) and risk of development of adverse effects such as serious infections, skin, and soft tissue infections and malignancies using data from randomized controlled trials (RCTs) and database registries in patients with rheumatoid arthritis, psoriatic arthritis, and ankylosing spondylitis. The gene discussed is TNF; the disease is psoriatic arthritis.