Each year, around 8 million (14.3%) deaths worldwide are attributable to mental health disorders.
According to the National Alliance on Mental Illness (NAMI), around 61.5 million Americans - the equivalent to 1 in 4 - experience some form of mental disorder in any given year. Around 13.6 million Americans have a serious mental illness, such as bipolar disorder, schizophrenia or major depression.
Past studies have suggested that people with mental illness have a higher mortality risk. In 2012, for example, Medical News Today reported on a study by researchers from University College London in the UK that found people who experience depression, anxiety and other mental health issues have a lower life expectancy than people without these conditions.
But the researchers of this latest study - including Elizabeth Reisinger Walker, PhD, of Emory University in Atlanta, GA, note that to date, no comprehensive meta-analyses have quantified the mortality risk in people with mental illness.
"Quantifying and understanding the excess mortality among people with mental disorders can inform approaches for addressing this persistent issue and widen discussion of the effect of mental disorders on mortality," say the authors.
Around 8 million deaths a year caused by mental health disorders
Walker and colleagues conducted a review of 2,481 studies that looked at the association between mental health disorders - including depression, anxiety, schizophrenia and bipolar disorder - and mortality.
The researchers included 203 studies in their final analysis, which represented 29 countries over six continents. These studies either compared the mortality risk of people with mental health disorders against that of the general population or people without mental illness.
The results of the analysis revealed that the mortality risk of people with mental health disorders was 2.22 times higher than the mortality risk of individuals free of mental illness and the general population. There was an average of 10 years of potential life lost among people with mental illness.
The team also found that natural causes accounted for 67.3% of deaths among people with mental health disorders. Unnatural causes accounted for 17.5% of deaths, while the causes of the remaining deaths are unknown.
In addition, the researchers calculated that each year, around 8 million (14.3%) deaths worldwide are attributable to mental health disorders.
Commenting on their findings, the authors write:
"People with mental disorders experience a high burden of mortality at the individual and population levels. Reduction of this burden will require a focus on less prevalent but more severe diagnoses and more common mental disorders. Likewise, efforts must be made to prevent and manage comorbid medical conditions and reduce the occurrence of unnatural deaths in this vulnerable population."
The team says their research is subject to some limitations. For example, they only included studies that had been published in English, meaning some may have been overlooked. "However, given the number of studies included in our analysis, it is unlikely that the results would be substantially affected," they note.
Furthermore, the authors say they were unable to assess mortality as a result of substance use disorders, noting that this is something that should be addressed in future research.