The positive qualities of dark chocolate, such as potentially increasing the release of serotonin and endorphins, have been well established. Other studies have suggested it boosts good gut bacteria, as well as increasing blood flow to the brain. Now for the first time, a study has looked at its impact on depressive symptoms, compared to other types of chocolate.

Researchers at University College London (UCL) and the University Of Calgary, Canada, looked at 140,000 adults from the US National Health and Nutrition Examination Survey. Participants' chocolate eating habits were assessed against their scores on the Patient Health Questionnaire, which analyses depressive symptoms.

The cross-sectional study, published in Depression and Anxiety, took factors such as weight, height, ethnicity, smoking, household income, marital status, education, and physical and chronic health problems into account whilst assessing the people involved.

The researchers found no link between milk chocolate consumption and depressive symptoms. However, eating dark chocolate was linked to a 70% lower chance of experiencing depression than those who didn't eat chocolate at all. The 25% who consumed all kinds of chocolate were also less likely to experience depression than those who ate none at all.

"This study provides some evidence that consumption of chocolate, particularly dark chocolate, may be associated with reduced odds of clinically relevant depressive symptoms." The lead author from UCL, Dr Sarah Jackson, said.

“However further research is required to clarify the direction of causation - it could be the case that depression causes people to lose their interest in eating chocolate, or there could be other factors that make people both less likely to eat dark chocolate and to be depressed."

Dark chocolate has also been associated with a reduced risk of heart disease and lower levels of 'bad' cholesterol. However, due to its high sugar content, it should be consumed in moderation, as part of a balanced diet.