The "back-to-work blues", while not a formal syndrome, are commonplace, with workplace stress a significant source of anxiety and depression in our lives, experts say.

A senior lecturer at Macquarie University, Barbara Griffin, said research indicated the blues were linked to sadness that pleasurable activities were over, and changes in food, alcohol and sleeping patterns during holidays.

"We can reset our body clock, so coming back to work is a lot like going through a daylight saving change," she said.

How we cope with our return to work, and how quickly the benefits of holidays ''fade out'', could be linked to what we did with our time off.

"In the short-term the effect of holidays does tend to wear off after three weeks to a month," she said. "The fade-out effects are quicker if we face a lot of work when we get back.

"You also have less effective holidays if you do work activities, or a lot of thinking about work.''

Dr Griffin said that despite the ease with which holidays faded there was plenty of evidence that taking them improved our health and wellbeing in the long-term.

"We can also delay the fade-out effect by taking time to relax in the evenings," she said.

Feeling depressed at being back at work while others were relaxed and renewed by the break did not necessarily mean you were in the wrong job, she said. It could be related to personality types or different holiday experiences.

The chief executive of beyondblue, Kate Carnell, said when returning to work or study after a holiday it was normal for people to feel a bit down for a few days.

"That said, if your feelings about it are more than just 'oh bugger, no more holidays for a while, isn't that depressing', if you are feeling incredibly stressed or agitated, are not able to sleep or are experiencing quite significant mood changes, it does suggest it's not just those normal feelings, and it's important to get some help.''

Beyondblue has three online programs available through its website that aim to help people identify mental health problems in the workplace.

Ms Carnell said research indicated about 17 per cent of depression and anxiety among women, and 13 per cent among men, was directly related to workplace stress.

"For many people work is a really, really stressful place to be … and this can really significantly impact on your performance in the workplace," she said. "This is a really important time for employers and other leaders in the workforce like the union movement to make our workplaces more mental-health friendly.''

The drive into work was smooth for motorists on Monday morning, despite the crowds returning to work. A spokeswoman for the Traffic Management Centre said while there was an increase in traffic, Sydney's roads were generally free-flowing. ''There's obviously still quite a lot of people on holidays.''

with Sherrill Nixon