Employees who work long hours and are habitually overworked are a staggering 15 times more likely than average to develop depression, a new Japanese study has found.
Dr Takahashi Amagasa and Dr Takeo Nakayama of Kyoto University School of Public Health analysed the job and workplace factors affecting depression risk in a group of 218 Japanese clerical workers. They found that employees who worked long hours (defined as at least 60 per week) and had high job demands (defined as "usually" having too much work) were at a much higher risk of depression. In fact, workers who initially had this so-called "LHO" (long hours overwork) combination were 15 times more likely to have depression when re-evaluated one to three years later.
The study, published in the August Journal of Occupational and Environmental Medicine, also found that when other factors were adjusted for, workers who went from LHO to non-LHO status were at lower risk of depression, while those who moved from non-LHO to LHO were at an even greater risk. The risk of depression in LHO workers seemed to increase over time.
Although previous studies have reported mixed results regarding the physical and mental health effects of long work hours, there is considerable evidence to suggest that it can lead to potentially devastating consequences.
For example, a 2007 study by Finnish researchers found that men who worked for a downsized company were 50 per cent more likely to be given a prescription for drugs such as antidepressants or sleeping pills than those whose had not been through a period of redundancies.
The same team had earlier found that that male workers classed as having "low justice in decision making procedures" – in other words, little control over their working lives and environment - had a 41 per cent higher risk of sickness absence than their high justice equivalents, while people who work in offices with low morale or high tension much more likely to be diagnosed with a depressive disorder than those who worked in open, laid-back office environments.
And if you still adhere to the old cliché that "hard work never hurt anybody", consider one of the largest and longest-running workplace studies ever carried out, which has been following the health of more than 10,000 British civil servants since 1985. Run by researchers from University College London, it has found – among many other things – that working more than 11 hours a day increases the risk of heart disease by 67 per cent.
That's corroborated by the Fukuoka Heart Study Group in Japan, who found that working over 60 hours a week and missing out on sleep can as much as double the chances of a heart attack for the 40+ age group.
According to Drs Amagasa and Nakayama, their study highlights the importance of the twin factors of high job demands and feeling overworked - combined with long working hours - as a trigger for depression. "By targeting LHO, especially changes in LHO status, mental health measures that effectively reduce the occurrence of major depressive disorder will become possible by controlling factors in the occupational environment," they conclude.