Mental Health in the Workplace: Numerous studies show that work is the primary source of stress for American adults, and it has been getting progressively worse. Increased levels of job stress have been associated with increased risk of heart attack, hypertension, and other disorders. This not only causes suffering for individual employees, but also negatively affects businesses and the economy as a whole. Based on research by Harvard University Medical School, untreated mental illness costs the US a minimum of $105 billion in lost productivity each year. Most organizations' health plans cover physical ailments, while mental health problems lag far behind. Serious mental illnesses cost society nearly $200 billion in lost earnings per year.