Almost nine million people in England – roughly one in six of the population – were prescribed an antidepressant last year.

The pills have long been hailed as life-changing treatments for depression and anxiety, helping to relieve symptoms by boosting the ‘feel good’ brain chemical serotonin.

But what was once more commonly a treatment measured in months is increasingly stretching far beyond that.

Around half of those prescribed antidepressants have been taking them for more than two years, official figures show, while one quarter – equivalent to around two million people – have used them for more than five years.

Many argue that is a good thing. Severe depression, which affects about one in 20 adults, is a serious illness, and some research has found long-term antidepressant use is a vital tool in reducing the risk of relapse and suicide.