Researchers have found that chocolate can make some people who are prone to depression less anxious and less irritable.

On the downside, it is laden with fat and sugar. But now it seems chocolate has a definite upside as an anti-depressant.

A study of 3,000 people by the Black Dog Institute found 45 per cent of people with depression craved chocolate.

"Of those 45 per cent, 60 per cent found that the chocolate improved their mood when they were depressed," Joanne Crawford, study co-author said.

Researchers found that among the depressed, those who were anxious or worriers were more likely to benefit from the sweet treats.

They believe it is the endorphins and opoids in chocolate which make people feel more relaxed.

"The opoids are morphine-like and lower pain and that also flows through into mental wellbeing," Professor Gordon Parker from the Black Dog Institute said.

Swimming star John Konrads battled depression, often turning to chocolate when he felt low.

"I thought it was a pick-me-up, almost like a cup of coffee, but to hear that it's a soother makes sense to me with hindsight," he said.

While it is too early for doctors to start prescribing chocolate for depression, this study does prove that it has tangible benefits in fighting mood disorders.

"I think this will be reassuring to many people who will say this just merely confirms what I have found out over the years," Professor Parker said.

The only caveat is that even as an anti-depressant, when it comes to chocolate, moderation is the key.