Scotland's national poet Robert Burns may have suffered from depression, according to academics.

The team from the University of Glasgow said its study of 800 letters and journals written by the bard suggests he had bipolar disorder.

Researchers said the condition could help explain his periods of intense creativity and unstable love life.

In one letter from December 1793, Burns describes himself as feeling "altogether Novemberish, a damn'd melange of fretfulness and melancholy".

He added that he felt his "soul flouncing and fluttering".

The team said two of the letters met the criteria for clinical depression and that gaps where the poet appeared to have written no letters could indicate social withdrawal.

Letters from 1787 show further evidence of depression and anxiety about "being exposed to the public" after a trip to Edinburgh.

Lead researcher Moira Hansen said: "'Blue devilism' was the term Burns used to describe periods of depression which he suffered, periods which affected his life and his work.

"Not something you would automatically expect of someone with a worldwide reputation for knowing how to enjoy himself."

She added: "The work published in this article shows that we can use Burns' letters as a source of evidence in place of having the face-to-face interviews a psychiatrist would normally have."

The team's findings have been published in the Journal of the Royal College of Physicians of Edinburgh.