Overtime can make your wallet smile, but your insides weep.

A new study shows people who work overtime regularly are more than two times as likely to experience a new "major depressive episode" than their counterparts who work a standard work day.

The British-based study suggests workers who stay on the job for at least 11 hours per day were up to 2.43 times more likely to experience new depression events when compared to workers who punched between seven and eight hours daily.

The study, which had one Canadian contributor from Montreal's McGill University, looked at more than 2,000 middle-aged British civil servants for an average of nearly six years — with more than three-quarters of those involved being male — and while it does not clearly identify a firm relation, its authors say the strong suggestion is there.

"Working overtime predicted the onset of a major depressive episode in a middle-aged cohort of British civil servants," reads the study, which was published this month in the peer-reviewed scientific journal PLos ONE.

"Working 11 or more hours a day was associated with a 2.3- to 2.5-fold risk of a (depressive episode) when compared with working a standard seven to eight hours a day."

The study was a followup to numerous other inquiries into the same topic that have produced inconclusive results when examining the link between overtime and depression.

The issue has been explored by other research, including one Canadian study that found overtime was also associated with depressive episodes, but only in women.

Kate Harkness, a psychology professor at Queen's University in Kingston, Ont., says overtime and inconsistent hours, when not managed properly, have long shown negative effects on personal health.

"What's actually really most critical is changing hours — for example, shift work or working overtime some days and not other days," Harkness said Friday. "That changing pattern strongly predicts mood episodes, both depressive episodes, but also manic episodes in people who are vulnerable to bipolar disorder.

"That change in schedule — and particularly overtime — is stressful and usually that means the person is overworked . . . and they have more work than they can do in the eight hours. That stress also releases chemicals in the brain that are associated with onsets of depression and mania."

The latest research found that there were "no robust associations between marital status, smoking, job strain or work social support and the onset of depression."

While the study shows strong potential links, its authors say further large-scale studies are needed, which would gauge the workforce outside the public service and look at various demographics.

Harkness suggests trying to keep up regular eating and sleeping schedules, regardless of the amount of hours worked or when they occur.

Other measures, such as regular exercise, can also "counterbalance" any additional stress that could lead to depression, Harkness said.

bbouzane@postmedia.com