Even relatively mild stress can lead to long term disability and an inability to work, reveals a large population based study published online in the Journal of Epidemiology and Community Health.

It is well known that mental health problems are associated with long-term disability, but the impact of milder forms of psychological stress is likely to have been underestimated. This study provides information on long-term consequences of these relatively mild symptoms, says lead study author Dheeraj Rai, MBBS, MRCPsych, from the University of Bristol in the United Kingdom.

Between 2002 and 2007, the authors tracked the health of more than 17,000 working adults up to the age of 64, who had been randomly selected from the population in the Stockholm area. All participants completed a validated questionnaire (GHQ-12) at the start of the study to measure their mental health and stress levels, as well as other aspects of health and wellbeing.

During the monitoring period, 649 people started receiving disability benefit - 203 for a mental health problem and the remainder for physical ill health.

Higher levels of stress at the start of the study were associated with a significantly greater likelihood of subsequently being awarded long term disability benefits.

But even those with mild stress were up to 70% more likely to receive disability benefits, after taking account of other factors likely to influence the results, such as lifestyle and alcohol intake.

One in four of these benefits awarded for a physical illness, such as high blood pressure, angina, and stroke, and almost two thirds awarded for a mental illness, were attributable to stress.

The authors say that it is important to consider their findings in the context of modern working life, which places greater demands on employees, and social factors, such as fewer close personal relationships and supportive networks.

These factors lead them to ask: "Are the strains and demands of modern society commonly exceeding human ability?" And they conclude that while mild stress should not be over-medicalised, their findings suggest that it should be taken more seriously than it is.