Long commutes are hitting the health and productivity of workers, leading to stress and depression, according to a new study.

Research among 34,000 adults found that those spending less than half an hour going to work gain an extra seven days’ worth of productive time every year.

But commuters travelling on trains between Glasgow and Edinburgh will have a longer wait for a shorter commute after fresh delays to electrification on the line.

New trains were due to start running in July but Network Rail had said a "safety-critical" component had failed.

It was hoped that journey times between the country’s biggest cities would be cut by ten minutes to 42 minutes by next year.

Private health firm VitalityHealth carried out research which showed a shorter commute could bring significant health benefits.

The study, delivered in partnership with the University of Cambridge, RAND Europe and Mercer, examined the impact of commuting as well as flexible and home working on employee health and productivity.

Researchers found that employees commuting less than half an hour to get to work gain an additional seven days’ worth of productive time each year compared to those with commutes of 60 minutes or more.

Longer commutes appear to have a significant impact on mental wellbeing, with longer-commuting workers 33 per cent more likely to suffer from depression, 37 per cent more likely to have financial concerns and 12 per cent more likely to report multiple dimensions of work-related stress.

These workers were also 46 per cent more likely to get less than the recommended seven hours of sleep each night and 21 per cent more likely to be obese.

Shaun Subel, of VitalityHealth, said: “These results demonstrate the significance of the daily work routine in influencing individuals' health and productivity.

“Beyond looking at ways that the work environment can be altered to make it more conducive to improved health and wellbeing, our research suggests that employers should perhaps be looking at flexible working arrangements as a more prominent part of their workplace wellness or productivity management strategy.

“Allowing employees the flexibility to avoid the rush-hour commute where possible, or fit their routine around other commitments, can help reduce stress and promote healthier lifestyle choices and, importantly, this is shown to actually impact positively on productivity.”

Network Rail chief executive Mark Carne revealed delays to the upgrade in a letter to the transport minister last week.

It said: “Regrettably, it is now clear that a safety critical component is susceptible to failure and must be replaced. This will impact the energisation start date.

“We are working extremely closely and collaboratively within the ScotRail Alliance to assess how the impact of this challenge can be minimised for passengers and we will keep your officials fully informed.”

Despite problems for rail commuters, drivers using the M8 between Glasgow and Edinburgh are enjoying quicker journeys.

The so-called missing link of Scotland's busiest motorway between Newhouse and Baillieston opened last month.

It is the latest stage in the £500m M8 M73 and M74 motorway improvements project which will cut journey times at peak times by around 20 minutes, according to Transport Scotland.