In a large new study, people with bipolar disorder were more likely than those without the mental illness to die from a number of causes, and to die almost a decade younger.
An expert on the condition, which is best known for including extreme swings in mood and energy levels, said the new findings illustrate a poorly understood point about the physical effects of the disease.
"Whatever we're doing, these people are not dying (just) because of suicide. That's not the reason for increased mortality. That's a hard thing to get across," said Dr. David Kupfer, a professor of psychiatry at the University of Pittsburgh School of Medicine, who was not involved in the study.
It's estimated that between 1 percent and 5 percent of people worldwide have bipolar disorder.
Previous research has found that people with the illness tend to die early from heart disease and suicide, but the effects of other chronic conditions remained unclear.
For the new study, Dr. Casey Crump from Stanford University in California and his colleagues analyzed data on about 6.6 million adults living in Sweden between 2003 and 2009. Of those, 6,618 had bipolar disorder.
During that time, people with bipolar disorder died, on average, about nine years younger than people in the general population.
And rates of death from any cause - about 14 deaths per 1,000 people in the general population every year - were double that among bipolar people.
Suicide was a major risk with bipolar disorder - women with the condition were 10 times more likely to kill themselves than the general population and men were 9 times more likely, Crump's team reported in JAMA Psychiatry on Wednesday.
But bipolar sufferers were also at raised risk of dying from heart disease, diabetes, chronic obstructive pulmonary disorder, the flu and pneumonia, compared to the general population.
People with bipolar disorder who knew they had those physical illnesses, however, had death rates similar to people who were not bipolar, according to the researchers, who suggested "that timely medical diagnosis and treatment may effectively reduce mortality among bipolar disorder patients to approach that of the general population."
As for why people with bipolar disorder may be more likely to die over a certain period of time than others, the research suggests a few possibilities, including that they may be less likely to get medical care and the disorder may affect the body itself.
Also, some medicines used to treat bipolar disorder have been linked to the development of a collection of risk factors for heart disease, known as metabolic syndrome.
In the study, Crump and his colleagues found that some medications for bipolar disorder were linked to an increased risk of death, but those who took no medications to treat their disorder had an even higher risk of death.
Kupfer said the study's findings support people with bipolar disorder getting medical workups to find other conditions, and having those conditions managed by doctors.
"It's not just physicians that need to know this. I strongly believe in patient and family education," he said.