It has been known for decades that mental health plays an important role in our quality of life, but a new study suggests it is also an important factor in our quantity of life.

The new study, led by researchers at the University of Toronto, followed 12,424 Canadians over the age of 18 from the mid-1990s until 2011. They discovered that the people who were in poor mental health at the beginning of the study died, on average, 4.7 months earlier than the people who were in excellent mental health.

Participants were first interviewed in 1994 and 1995 (Wave 1) and were followed until 2010 and 2011 (Wave 9).

Mortality data was ascertained by the Canadian Vital Statistics-Death Database in Wave 9. By the end of the study period, 2,317 of the participants had died, according to the researchers.

The study took into account the “usual suspects for premature mortality” including the study participants’ functional limitations; health behaviors, such as smoking, heavy drinking, and physical activity level; physical diseases, such as cancer, heart disease, diabetes, and chronic pain; and social support at the beginning of the study.

“As expected, modifiable risk factors, including smoking, heavy drinking, and infrequent physical activity, were associated with a higher probability of all-cause mortality,” said co-author Dr. Philip Baiden, an assistant professor of social work at the University of Texas at Arlington.

“Cancer, heart disease, diabetes, chronic obstructive pulmonary disease, and high blood pressure were associated with a higher probability of death over the follow-up period.”

But even after fully adjusting for all the risk factors, the researchers “still found that those with suboptimal mental health at the beginning of the study had a 14 percent higher risk of all-cause mortality over the 18 years of the study,” said Dr. Esme Fuller-Thomson, lead author of the study, a professor at the University of Toronto and director of the university’s Institute for Life Course and Aging.

For the study, researchers created a “flourishing indicator” to identify people who were happy and satisfied with life and had good psychological functioning at the beginning of the study in 1994 and 1995.

“The flourishing scale we developed set a very high bar,” says Yu Lung, a doctoral student at the university.

According to the researchers, at the start of the study, 81 percent of the people participating were flourishing, while 19 percent were in suboptimal mental health.

Unfortunately, the study’s secondary data analysis did not have sufficient information to understand why excellent mental health is associated with longer life, the researchers say.

“We have several hypotheses that we would like to investigate in future research,” said co-author Keri J. West, a doctoral candidate at the University of Toronto. “Previous research has found that positive affect is associated with lower levels of cortisol, reduced inflammation, and better cardiovascular activity. Furthermore, individuals with high levels of mental well-being are more likely to consume nutritious foods, adhere to treatment regimens, maintain strong social ties, and have better sleep quality, which may contribute to longevity.”

“The association between suboptimal mental health and premature death is a robust relationship that is independent of health conditions, pain, functional limitations, and negative health behaviors at baseline,” Fuller-Thomson added. “Our findings underline the importance of considering the mind and body as a true continuum.”

The study was published in the Journal of Psychosomatic Research.

Source: University of Toronto