Speaking at the launch of the Capita Employee Benefits Employee Insight Report 2014, Dornan said the effect of long-term unemployment "can be very detrimental to people's physical and mental health, especially around stress and depression".
He added that, as the economy improves and more people return to work, employees who have become unaccustomed to workplace stress may exacerbate this problem.
"When people come back to work after a long period of unemployment, you will often find that their attitudes towards things like pride in an employer and trust can be damaged," he said. "Employers should be aware of that and try to help them."
Figures from the Capita report reveal that 79% of employees say they have suffered from stress at work over the past 12 months. Twenty percent reported taking time off for stress over the same period.
Employees between 16- and 24-years-old are most likely to take time off for stress. Almost one-third (30%) have done so in the past year. A similar proportion (29%) of 25- to 34-year-olds have been absent through stress, compared to 12.4% of workers aged between 45 and 64.
