People with high IQ are considered to have an advantage in many domains. They are predicted to have higher educational attainment, better jobs, and a higher income level. Yet, it turns out that a high IQ is also associated with various mental and immunological diseases like depression, bipolar disorder, anxiety, ADHD as well as allergies, asthma, and immune disorders. Why is that? A new paper published in the journal Intelligence reviews the literature and explores the mechanisms that possibly underlie this connection.