As automation advances, predictions of a jobless future have some fearing unrest from mass unemployment, while others imagine a more contented work-free society.
Aside from economic factors, paid employment brings other benefits - often psychological - such as self-esteem and social inclusion. Now, researchers at the universities of Cambridge and Salford have set out to define a recommended "dosage" of work for optimal wellbeing.
They examined how changes in working hours were linked to mental health and life satisfaction in over 70,000 UK residents between 2009 and 2018*.
The study, published today in the journal Social Science and Medicine, shows that when people moved from unemployment or stay-at-home parenting into paid work of eight hours or less a week, their risk of mental health problems reduced by an average of 30%.
Yet researchers found no evidence that working any more than eight hours provided further boosts to wellbeing. The full-time standard of 37 to 40 hours was not significantly different to any other working time category when it came to mental health.
As such, they suggest that to get the mental wellbeing benefits of paid work, the most "effective dose" is only around one day a week - as anything more makes little difference.
"We have effective dosage guides for everything from Vitamin C to hours of sleep in order to help us feel better, but this is the first time the question has been asked of paid work," said study co-author Dr Brendan Burchell, a sociologist from Cambridge University who leads the Employment Dosage research project.
"We know unemployment is often detrimental to people's wellbeing, negatively affecting identity, status, time use, and sense of collective purpose. We now have some idea of just how much paid work is needed to get the psychosocial benefits of employment - and it's not that much at all."
Supporting the unemployed in a future with limited work is the subject of much policy discussion e.g. universal basic income. However, researchers argue that employment should be retained across adult populations, but working weeks dramatically reduced for work to be redistributed.
"In the next few decades we could see artificial intelligence, big data and robotics replace much of the paid work currently done by humans," said Dr Daiga Kamerāde, study first author from Salford University and Employment Dosage researcher.
"If there is not enough for everybody who wants to work full-time, we will have to rethink current norms. This should include the redistribution of working hours, so everyone can get the mental health benefits of a job, even if that means we all work much shorter weeks."
"Our findings are an important step in thinking what the minimum amount of paid work people might need in a future with little work to go round," she said.
The study used data from the UK Household Longitudinal Study to track the wellbeing of 71,113 individuals between the ages of 16 and 64 as they changed working hours over the nine-year period. People were asked about issues such as anxiety and sleep problems to gauge mental health.
Researchers also found that self-reported life satisfaction in men increased by around 30% with up to eight hours of paid work, although women didn't see a similar jump until working 20 hours.
They note that "the significant difference in mental health and wellbeing is between those with paid work and those with none", and that the working week could be shortened considerably "without a detrimental effect on the workers' mental health and wellbeing".
The team offer creative policy options for moving into a future with limited work, including "five-day weekends", working just a couple of hours a day, or increasing annual holiday from weeks to months - even having two months off for every month at work.
They also argue that working hour reduction and redistribution could improve work-life balance, increase productivity, and cut down CO2 emissions from commuting. However, they point out that reduction of hours would need to be for everyone, to avoid increasing socioeconomic inequalities.
"The traditional model, in which everyone works around 40 hours a week, was never based on how much work was good for people. Our research suggests that micro-jobs provide the same psychological benefits as full-time jobs," said co-author and Cambridge sociologist Senhu Wang.
"However, the quality of work will always be crucial. Jobs where employees are disrespected or subject to insecure or zero-hours contracts do not provide the same benefits to wellbeing, nor are they likely to in the future."
Dr Burchell added: "If the UK were to plough annual productivity gains into reduced working hours rather than pay rises, the normal working week could be four days within a decade."
*In all the statistical models used in the research, individual and household characteristics that influence employment status, work hours and mental wellbeing were controlled for. These included age, children, longstanding illness and household income.