Probability of Having an Autoimmune Disease

Autoimmune diseases collectively affect approximately 24 million Americans (about 8% of the population), though some estimates that include broader diagnostic criteria suggest the number could be as high as 50 million. There are over 80 known autoimmune diseases, and women account for approximately 78% of those affected.

The most common autoimmune diseases include Hashimoto's thyroiditis, rheumatoid arthritis, type 1 diabetes, psoriasis, inflammatory bowel disease (Crohn's and ulcerative colitis), celiac disease, lupus, and multiple sclerosis. Having one autoimmune disease significantly increases the risk of developing another (about 25% of patients have multiple autoimmune conditions).

The exact causes of autoimmune diseases remain unclear, but they involve a combination of genetic susceptibility, environmental triggers (infections, gut microbiome changes, toxin exposure), and hormonal factors (which may explain the female predominance). Treatment has been revolutionized by biologic therapies targeting specific immune pathways, but most autoimmune diseases remain chronic conditions requiring lifelong management. The NIH spends about $1 billion per year on autoimmune disease research. Autoimmune disease prevalence appears to be increasing globally, with some studies showing rates doubling over the past 30 years.