(CNN) - Around the world, people with mental illness die up to 20 years earlier than the general population, and a comprehensive new report suggests that governments and health care providers must do more to stop the deaths.
"The disparities in physical health outcomes for people with mental illness are currently regarded as a human rights scandal," said Joseph Firth, a research fellow at the University of Manchester and chairman of the Lancet Psychiatry Commission, which published the research.
His team analyzed nearly 100 studies and found that most people with mental illness die early not because of suicide -- although those account for about 17% of unnatural deaths -- but because of "poor physical health" that could be largely preventable.
People with mental health disorders face up to twice the risk of cardiometabolic diseases such as diabetes and stroke, researchers found. In people with depression, for example, the risk of cardiac disease, diabetes or obesity is about 40% higher than in the general population.
Mental illness can increase the risk of physical disease, and physical disease itself increases the risk of mental illness, Firth said. "Having obesity or diabetes increases your risk causally of developing a psychiatric condition, and vice versa."
Sometimes, that's because treatments for mental illness can trigger or worsen physical health problems. The report found, for example, that many drugs used to treat mental illnesses -- including antidepressants, antipsychotics and mood stabilizers -- can have adverse effects on metabolism and heart health.
"As a result, patients who gain weight have a reduced adherence to treatment, which can lead to relapse and poor mental health outcomes," the report said. The drugs still "do more good than harm," Firth added, but he emphasized that doctors need to monitor and manage any adverse effects.
People with mental illness receive poorer care
Almost all mental illnesses are also associated with some lifestyle risk factors -- behaviors that make diseases such as heart disease more likely -- and "people with mental illness tend to have more unhealthy lifestyles compared with the general population," the report found.
People with major depression are more likely to smoke and be dependent on nicotine, for example, and have a significantly worse diet than the general population, according to the researchers. Almost one in five people with anxiety disorders misuse alcohol, and those with social phobia report less physical activity.
But even after controlling for risk factors such as smoking, physical activity and body mass index, the report found that deaths remained higher in those with mental illness. That suggests people with mental illness receive poorer care than those without psychiatric problems, researchers said.
For example, the report found that people with severe mental illness are less likely to have a physical examination than their peers. They also have more emergency department visits and hospital admissions for conditions that should be avoidable and could be prevented with appropriate primary care.
It's unclear exactly why that's the case, but one possible explanation is that doctors mistakenly attribute physical symptoms to underlying psychiatric problems, leading to missed diagnoses, researchers said.
The report also found that people with mental illness are less likely to receive medical and surgical interventions that are offered to the general population. And healthcare services can be intolerant of people with mental illness, or at least perceived as such, the report said.
Healthy body, healthy mind
"More needs to be done to address stigmatising attitudes towards mental health, and the education and practice of health-care providers needs to be reoriented towards integrating physical and mental health care," wrote Rakhi Dandona, a clinical professor of health metrics sciences at the University of Washington, in an accompanying editorial.
"In some areas, it is clear there has been a willful abandonment of the mentally ill due to stigma and discrimination of these populations, due to people not really looking after them," said Firth, who worked with more than 40 other experts to compile the most recent report.
"You can look at the amount of funding, for instance, spent on mental health care and mental health research compared to all aspects of health, and you can see that there are large disparities there," he added.
But health care systems are working to offer better care, Firth said. "More and more world health authorities and national health bodies are genuinely doing their best to try to address these health issues," he said, both to help patients and cut costs.
"We do need to start addressing the mind and the body together," said Firth. "It sounds like a very old-age saying of 'healthy body, healthy mind.' But looking at the data, that's so well-supported that it's almost impossible to imagine an effective treatment system where we keep these two things separate."
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