Fizzy drinks and fruit squashes are being linked to depression in a study involving more than 250,000 people.
Downing four cans of sparkling drinks a day raised the risk of mental illness by 30 per cent, while the same amount of squash increased it by 38 per cent, researchers said.
The danger was greatest for those who opted for diet products. However, people drinking four cups of coffee a day were ten per cent less likely to develop depression.
Reseacher Dr Honglei Chen said: 'Cutting down on diet drinks or replacing them with unsweetened coffee may help lower your depression risk.'
The findings come from a US study looking at 263,925 people's consumption of soft drinks, tea and coffee between 1995 and 1996.Ten years later, 11,311 of participants aged between 50 and 71 at the start of the study were found to have been diagnosed with depression.
Emer O'Neill, from the Depression Alliance, said: 'We're really pleased to see that research continues to be done in order to raise awareness. Diet has a huge impact on mood and fizzy drinks, alcohol, caffeine can have a negative impact on a person's health when consumed excessively.'
However, the British Soft Drinks Association said the study failed to address other factors, such as family history, and more research was needed.