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Mental health may not just influence quality of life, but also quantity of life. 

A study from researchers at the University of Toronto found that those with suboptimal mental health died earlier than their counterparts with excellent mental health.

“Those who were in excellent mental health when the study started in the mid-1990s lived almost five months longer than their peers who were in poorer mental health,” Esme Fuller-Thomson, lead author of the study and Director of the University of Toronto's Institute for Life Course and Aging told Theravive.

The researchers followed 12, 424 adults in Canada beginning in the mid- 1990s and up until 2011.

A “dichotomous flourishing indicator” was made to identify those who were satisfied with life, were happy and who had good level of psychological functioning during 1994 and 1995 at the start of the study.

“The flourishing scale was constructed of two parts: one happiness and satisfaction in life; and two positive psychological functioning… for example, sense of purpose, or self-esteem. You had to have both of these elements to be defined as flourishing. If you lacked one or both of these elements you were defined as having ‘suboptimal mental health’. In 1994 and 1995, most people were flourishing: 81 per cent of the sample were flourishing and 19 per cent were in suboptimal mental health,” Fuller-Thomson said. 

The researchers also accounted for typical factors for premature mortality including health behaviours like heavy smoking and heavy drinking, their activity level, social support, their functional limitations and any physical disease like cancer, diabetes, heart disease and chronic pain.

After adjusting to account for these factors, the researchers still found that those who had poor mental health at the start of the study had a 14 per cent greater risk of mortality from all causes over the 18-year study period. On average, they died 4.7 months earlier than their peers who had excellent mental health.

Their findings were reflective of earlier work undertaken in the US, which found that baseline suboptimal mental was associated with higher mortality over a ten-year period.

The authors note that their study did not have sufficient data to understand why having excellent mental health is associated with a longer lifespan. But Fuller-Thomson says the study still highlights the important of improving one’s own mental health.

“Our study was an observational study so all we can show is correlation, not causation.  We therefore cannot determine if improving mental health would increase the quantity of life.  However, we have known for decades that better mental health improves the quality of life, so it certainly makes sense to invest time and energy in enhancing one’s mental health. This is particularly true for those struggling with depression, anxiety, unhappiness or simply a lack of purpose or low self-esteem.There are very effective interventions such as cognitive behavioural therapy (CBT) that can help most people improve their mental health,” she said.

But the researchers have a few ideas why good mental health is associated with a longer life, and hope to explore this in future studies.

Prior studies have found that positive affect is tied to lower cortisol levels, reduction in inflammation and better cardiovascular health. As well as this, those with higher levels of mental wellbeing are more likely to maintain good social connection, have better sleep, eat more nutritious foods and stick to treatment regimens. These could all contribute to a longer life.

Modifiable risk factors like smoking, heavy drinking and infrequent physical activity were associated with higher risk for all-cause mortality. But the link between suboptimal mental health and premature death exists independently of health conditions, negative health behaviours, functional limitations or pain.

Fuller-Thomson says the study reinforces the importance of the mind-body connection.  

“Our findings suggest that there is truly a mind-body continuum. Both our physical and our mental health contribute to a fulfilling, long and healthy life.”