Mental illness is now the second largest reason for UK workers taking time off, a report suggests.
A rising number of workers are said to be suffering stress
A study by the Chartered Institute of Personnel and Development found an increasing amount of sickness leave is due to depression or stress.
Analysis of the records of 30,000 people found only muscle-related problems such as bad backs were cited as a greater cause of absenteeism.
Staff with depression were said to take an average 30 days off annually.
Those with stress were reported to be away for 21 days.
The CPID found public sector workers were more likely to take time off work because of mental illness and overall the problem was more prevalent among older staff.
The CIPD said its findings will be "particularly worrying" for the government in light of a "huge" increase in the number of people with mental health problems claiming incapacity benefit.
"This research shows how important it is for managers and HR practitioners to be aware of the signs of mental ill health so that they can take action early and provide support before the individual's condition deteriorates to the point they go off on long-term sick leave," said Ben Willmott, CIPD employee relations adviser.
He called on the government to provide tax incentives to encourage more firms to offer occupational health services.
GPs need to work more closely with employers to identify opportunities for "phased return-to-work" for those affected with less demanding or reduced hours roles, Mr Willmott added.