This document summarizes research on the relationship between physical and mental health conditions. It finds that around 16-20% of cancer patients experience depression, and rates of other mental health issues like anxiety are also elevated in various physical illnesses. Longer time since diagnosis is linked to higher rates of some mental health problems. Having a physical and mental health condition simultaneously is associated with much greater impairment and higher health care costs and mortality risk compared to having just one or neither. Integrated treatment of both physical and mental health issues is recommended.