The Depressing truth about overtime

The odds of a major depressive episode are more than double for those working 11 or more hours a day compared to those working seven to eight hours a day, according to a new study.

Researchers followed about 2000 middle aged British civil servants (as part of the ‘Whitehall II Study‘) and found a robust association between overtime work and depression. This correlation was not affected when the analysis was adjusted for various possible confounders, including socio-demographics, lifestyle, and work-related factors.

The study, published in the journal PLoS ONE today, found that people working more than 11 hours a day were 2.43 times more likely to have a major depressive episode than those who work 7-8 hours a day.

Although the study was not designed to determine exactly how overtime increased depression risk, the authors noted that:

“Long working hours may in part affect mental health through factors not measured in our study, such as work-family conflicts, difficulties in unwinding after work or prolonged increased cortisol [a stress hormone] levels.”

The authors also called for more research to evaluate the effectiveness of limiting work hours, stating:

“Service and intervention studies are needed to examine whether interventions designed to reduce working hours would alter depression risk in working populations.”

New Zealand statistics

The most recent New Zealand Census figures from 2006 for 1.83m workers showed 415,641  working 50 or more hours each week, (22.68 per cent of the workforce and 29.08 percent of full-time workers). Among full-time workers 36 percent of men work 50 or more hours a week, and 19 per cent of women.

Those with the highest qualifications, such as masters’ and doctorate degrees, are significantly more likely to work long hours, but the largest group of long hours workers are those who have no qualifications.

The Science Media Centre gathered the following comments on the research from New Zealand experts.

Feel free to use these comments in your reporting. To speak to an expert, please contact the Science Media Centre (04 499 5476;

Helena D Cooper-Thomas, Senior Lecturer, Psychology Department, The University of Auckland comments:

“The Whitehall studies have contributed significantly to our understanding of workplace health issues. The main result of this research is the finding that working long hours – in this study more than 11 hours per day – increases the risk of becoming severely depressed. This links well with research from Europe showing the importance of recovery activities in the evening after work.

“Employees who feel that they have used their leisure time to relax, recover, and experience a positive mood show more engagement and initiative at work the next day. This is also important for employers to take note of also – workers who have had more chance to recover are more engaged and proactive the next day.

“A second result that I also find interesting is that it is mid-level employees who are at higher risk of depression as compared to both more senior and the most junior employees. Workers in the middle ranks don’t have the same level of autonomy as those in the more senior roles, yet have considerable responsibility. Perhaps these workers are in the most precarious positions, balanced between potentially competing demands, and therefore experience more strain and consequently higher levels of depression.

“In New Zealand there is an emphasis on using leisure time well, and this suggests that workers in New Zealand should use their after-work hours to achieve relaxation and enjoyment. For anyone reading this who does not use their leisure time well, you should reflect on this further. A related issue is that, during work hours, we should use our time well and work efficiently to keep our leisure time free. Some organizations have macho long hours cultures, where being seen to work long hours is a sign of commitment to the organization or to one’s career.

“However research shows that working long hours is associated with poorer mental health, and that workers who use their leisure time to recover are more enthusiastic and proactive. Surely, then, both employers and employees should be aiming to work hard AND play hard.”

Dr Rebbecca Lilley, Research Fellow & Lecturer, Department of Preventive and Social Medicine, University of Otago, comments:

“The Whitehall II Study is a world renowned study of Public Sector workers that has contributed greatly to improving our understanding of work stress and it’s subsequent impact upon worker health, including the health conditions of cardiovascular disease and mental health.

“Examining overtime working hours as a form of a over-demanding work schedule is appropriate as there is little clear understanding of how over-demanding work schedules impact upon worker health.  The paper highlights how depression is a significant and rapidly growing public health concern internationally.  Increasingly we are understanding that work contributes significantly to the development of depression in workers.

“Little is known about the prevalence of depression in the New Zealand workforce.  A recently published study by myself and colleagues in New Zealand cleaners and clerical workers surveyed in May 2004-April 2005 found 11% of workers reported they were currently suffering from psychological distress and that job pressure was a risk factor for reporting psychological distress in this mainly female working population.

“The Whitehall II Study demonstrates with increasing overtime, over and above a standard working day of 7 hours per day, the risk of having a Major Depressive Episode increases, demonstrating a dose-response effect.  So the longer the overtime hours the greater the likelihood a person will develop a Major Depressive Episode.

“The authors carefully outline a long list of limitations to this study that need further investigation before plausible explanations of why long overtime work hours are associated with depression can be drawn.  One further limitation to this study is that while this group adjust their findings for potential socio-demographic, workplace, lifestyle and health explanatory factors there are some potential factors that have not been considered.   

“One such group of factors not examined by this group represent the lost opportunities by overtime workers to get sleep or to undertake physical activity.  As a person spends longer each day at work the opportunities to do these activities is reduced.  Both sleep quality and physical activity are risk factors for developing depression and could provide an alternate explanation for these findings.

“So, while this is an interesting analysis suggesting that working overtime is a risk factor for developing a Major Depressive Episode in Public Sector workers in the UK more research is required to fully understand the implications of the findings of this study for workers in general.  This paper will be important in stimulating further research in over-demanding work schedules and depression in working populations.”

Further commentary from the UK Science Media Centre:

Clare Bambra, Professor of Public Health Policy, Durham University, said:

“The link between working long hours and depression is very important. The UK has the longest working hours in Europe and many people are encouraged to work in excess of the EU working time directive – the 48-hour week.

“The economic crisis is likely to increase the pressure on those in-work to work longer hours. There is a strong public health need for employers and the government to consider limiting working hours and giving employees more control over their working hours.

“A recent Cochrane review led by Durham University researchers found that having more control over working hours improved physical and mental health.”

Dr Paul Keedwell, Honorary Consultant Psychiatrist, Cardiff University, said:

“This study confirms what we have long suspected – that we cannot expect to work long hours in stressful white-collar jobs without psychological ill effects. High socio-economic status does not protect you. More work is urgently required to examine if this link between overtime and depression is due to personality, job-specific strain, work-family conflict, neglecting important relationships, or all of the above.”

Professor Anthony Cleare, Professor of Affective Disorders, King’s College London Institute of Psychiatry, said:

“This important study reminds us that working conditions can markedly affect an individual’s mental health.  However, whilst there is a link between excessive hours and depression, it is important to be clear that many individuals do thrive on working longer hours and there should not be a blanket prohibition.

“Instead, we need to see long working hours as a potential risk factor in some people, and to understand more about which individuals are at particular risk.  One suggestion from this and other studies is that people lower down the working hierarchy, and who have less control over their jobs, may be especially at risk of depression.

“We should also not forget in these troubled times that being unemployed is probably even more detrimental to a person’s mental health.”