People with mental health problems may have shortened life spans, according to a recent study HealthDay reported.

Researchers from the University of Oxford in the United Kingdom found that serious mental illness can take seven to 24 years off a person's life, similar to or worse than the impact of heavy smoking, HealthDay reported.

"We found that many mental health diagnoses are associated with a drop in life expectancy as great as that associated with smoking 20 or more cigarettes a day," Dr. Seena Fazel, researcher from the department of psychiatry at the University of Oxford, said in a statement. "There are likely to be many reasons for this. High-risk behaviors are common in psychiatric patients, especially drug and alcohol abuse, and they are more likely to die by suicide."

Fazel added that the stigma surrounding mental health problems "mean people aren't treated as well for physical health problems when they do see a doctor."

For the study, researchers examined 20 studies involving more than 1.7 million people, and 250,000 deaths that looked at the link between mental illness and death rates.

They found that the average life expectancy for people with schizophrenia was 10 to 20 years shorter than normal and 9 to 20 years shorter for those with bipolar disorder. They also found that people with recurrent depression had a life expectancy 7 to 11 years shorter than normal.

Researchers said heavy smoking shortens life by an average of 8 to 10 years.

Although investigators found an association between mental illness and an increased risk of premature death, they did not prove that mental illness cause early death.

Researchers noted that mental illness is not a public health priority because of the tendency to "separate mental and physical health," HealthDay reported.

"Many causes of mental health problems also have physical consequences, and mental illness worsens the prognosis of a range of physical illnesses, especially heart disease, diabetes and cancer. Unfortunately, people with serious mental illnesses may not access health care effectively," Fazel said.

Researchers said their findings may push governments and health officials to place a much higher priority on mental health.

The findings were recently published in the journal World Psychiatry.