Although the specific societal impact of mental illness varies among cultures and nations, untreated mental illness has significant costs to society. In 2001, the WHO estimated that mental health problems cost developed nations between three and four % of their GNP (gross national product). When mental illness expenditures and loss of productivity are both taken into account, the WHO estimated that mental disorders cost national economies several billion dollars annually.(16) In 1997, a Harvard Medical School study estimated that the United States lost more than 4 million workdays and experienced 20 million “work cutback days” (days of impaired workplace performance) due to mental illness.(17)
In addition, psychological disorders can exacerbate other public health issues, increasing the burden on national economies and impeding international public health efforts. In 2001, at least five to ten million people worldwide used intravenous drugs, and five to ten % of new HIV infections were due to transmission via intravenous drug use.(18) Mental illnesses are also associated with increased risk of non-adherence to medical regimens for other health conditions. For infectious diseases, improper or incomplete use of medication can lead to drug resistance, which may have “profound public health implications” for the global community.(19) Furthermore, maternal depression may put infants at increased risk of low birth weight, childhood health problems, and “incomplete immunization”, all of which are risk factors for childhood mortality