Researchers say that combined, mental and substance use disorders were the leading cause of non-fatal illness worldwide in 2010, according to a study published in the The Lancet.
The study, conducted by researchers from Australia and the US, analyzed data from the Global Burden of Diseases, Injuries, and Risk Factors Study 2010 (GBD 2010).
The researchers looked at 20 mental and substance use disorders included in GBD 2010, then systematically reviewed the patterns, causes and effects of the disorders. They analyzed prevalence of the disorders by age, sex, country, region and year.
In order to calculate the years lived with disability (YLD), the researchers used community and internet-based surveys. Premature mortality was calculated as years of life lost (YLL) from cause of death estimates from 1980 to 2010 for 20 age groups, both sexes and 187 countries.
Disability-adjusted life years (DALYs) were calculated from the sum of years lived with disability and years of life lost.
Higher global death burden than HIV
Results of the analysis showed that mental and substance use disorders were the fifth leading cause of death and disease worldwide.
However, when looking at how mental and substance use disorders affected non-fatal illness only, it was found to be the leading cause, contributing to 22.8% of all disease burden.
The authors say that this difference in non-fatal illness compared with the cause of death and disease is supported by the fact that mental and substance use disorders caused a low death rate in 2010 at 232,000, relative to the overall illness they caused.
The study authors say:
"Mental and substance use disorders were the leading global cause of all non-fatal burden of disease (YLDs).
In 2010 they accounted for 175.3 million YLDs, or 22·9% of all non-fatal burden. Depressive disorders contributed most of the non-fatal burden of mental and substance use disorders followed up by anxiety disorders, drug use disorders, and schizophrenia."
The analysis also revealed that girls and women over the age of 14 showed a higher risk of death and disease from mental disorders compared with boys and men. But men showed a higher risk of death and disease from drug and alcohol dependence over all age groups.
Number of deaths 'potentially higher'
Although the majority of the deaths recorded were a result of substance use disorders alone, the researchers note that there is a high level of premature mortality in those who suffer from mental disorders. However, within GBD 2010, the study authors say deaths are "coded" to physical cause of death.
GBD protocol states that death by suicide is to be coded under "injuries," even though, the researchers note, the majority of suicide deaths are due to mental disorders.
Also, death from illicit drugs are frequently coded as "accidental poisonings." The study authors warn that although they tried to account for these different codings, the number of deaths caused by illicit drug use could be even higher.
'Resources needed' to deliver interventions
Some individual disorders analyzed showed significant variations over countries, with eating disorders showing the largest difference. The proportion of death and disease from eating disorders was 40 times higher in Australasia, compared with sub-Saharan Africa.
The burden of death and disease from mental and substance disorders were only statistically lower in China, North Korea, Japan and Nigeria, compared with the global average.
Professor Harvey Whiteford of the Queensland Centre for Medical Health Research at the University of Queensland, Australia, says this research shows that although cost-effective interventions are available for most disorders, adequate financial and human resources are needed to deliver these interventions worldwide, particularly in developing countries.
"Despite the personal and economic costs, treatment rates for people with mental and substance use disorders are low, and even in developed countries, treatment is typically provided many years after the disorder begins," adds Prof. Whiteford.
"In all countries, stigma about mental and substance use disorders constrain the use of available resources as do inefficiencies in the distribution of funding and interventions."
"If the burden of mental and substance use disorders is to be reduced, mental health policy and services research will need to identify more effective ways to provide sustainable mental health services, especially in resource constrained environments."