Everything you know about depression is wrong:

There is strong evidence that human beings need to feel their lives are meaningful - that they are doing something with purpose that makes a difference. It's a natural psychological need. But between 2011 and 2012, the polling company Gallup conducted the most detailed study ever carried out of how people feel about the thing we spend most of our waking lives doing - our paid work. They found that 13% of people say they are "engaged" in their work - they find it meaningful and look forward to it. Some 63% say they are "not engaged", which is defined as "sleepwalking through their workday". And 24% are "actively disengaged": they hate it.

Most of the depressed and anxious people I know, I realised, are in the 87% who don't like their work. I started to dig around to see if there is any evidence that this might be related to depression. It turned out that a breakthrough had been made in answering this question in the 1970s, by an Australian scientist called Michael Marmot. He wanted to investigate what causes stress in the workplace and believed he'd found the perfect lab in which to discover the answer: the British civil service, based in Whitehall. This small army of bureaucrats was divided into 19 different layers, from the permanent secretary at the top, down to the typists. What he wanted to know, at first, was: who's more likely to have a stress-related heart attack - the big boss at the top, or somebody below him?

Everybody told him: you're wasting your time. Obviously, the boss is going to be more stressed because he's got more responsibility. But when Marmot published his results, he revealed the truth to be the exact opposite. The lower an employee ranked in the hierarchy, the higher their stress levels and likelihood of having a heart attack. Now he wanted to know: why?

And that's when, after two more years studying civil servants, he discovered the biggest factor. It turns out if you have no control over your work, you are far more likely to become stressed - and, crucially, depressed. Humans have an innate need to feel that what we are doing, day-to-day, is meaningful. When you are controlled, you can't create meaning out of your work.