We spend around one-third of our lives at work. That’s around 90,000 hours of the limited time we have on Earth shuffling around our workplaces trying to complete tasks on our to-do lists. But – and this is a very big question – have you ever stopped and asked why?

Yes I know, and of course, the primary answer for almost everyone is to earn a regular income so we can spend it living a lifestyle that we want. However, there are a bunch of other positive benefits we get from our jobs.

Our work gives us social status, the type we tend to trade like verbal business cards when we’re at a dinner party. Work gives us social interactions, often with people of varied backgrounds that we mightn’t come across naturally in our well-worn social circles. Work gives us a time structure of where we need to be and when, and it gives us a sense, no matter how tiny, of meaning and purpose in the long years that add up to a career.

There’s little argument that we gain a combination of benefits from our employment, but there’s another a big question that we rarely ask, and it’s this: how much work do we actually need to do? If we hypothetically took money out of it, what is the minimum amount of work we must do to get all the positive psychological benefits from our jobs?

It’s a fascinating thought experiment with a surprising answer that a smart researcher spent years getting to the bottom of. A decade and a half ago, Dr Brendan Burchell, a professor at the University of Cambridge, was invited to give a talk on any topic. He wanted to know what was the optimal amount of paid work for employee wellbeing, and he quickly realised nobody else had answered it.

Dr Burchell called it the Employment Dosage Project, named after the idea that scientists often study exactly how much dosage we need of certain drugs to get a desired effect. He used data to track over 70,000 British residents between 2009 and 2017, following people over several years as their hours of work and levels of happiness changed.

It’s a stark reminder that we need to constantly challenge and question the preconceived notions that we have about hard work.

To the surprise of almost everyone around him, Dr Burchell and his team discovered that working just one eight-hour day delivered the same positive mental health benefits as working five full days a week. After a whole day, the positive benefits plateaued out, and it didn’t matter whether someone worked 8 or 48 hours, the results were the same.

This unexpected finding has since been confirmed in many other studies, and Dr Burchell often explains it by comparing it to vitamin C. You only really need a small amount of vitamin C to get all its benefits. Any less than the minimum dosage and you might get scurvy, but every amount above the small dosage that your body requires isn’t scientifically beneficial.