ANALYSIS of 800 letters and journals written by Robert Burns suggest he had bipolar disorder, according to academic researchers.

A team from the University of Glasgow said there is evidence of the Bard's moods cycling between "depression and hypomania" in his work and that the disorder could explain Burns' periods of intense creativity and unstable love life.

Claims about his mental health have been made before based on biographies of the writer, but the latest project, which started in 2014, looked at blocks of letters written over nine years of Burns' life, using modern psychiatry methods to analyse his state of mind.

The first block of letters from around December 1793, detailed Burns feeling "altogether Novemberish, a damn'd melange of fretfulness and melancholy ... my soul flouncing & fluttering".

Experts 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.

Another block of letters from early 1787 showed evidence of depression and anxiety "about being exposed to the public" after Burns travelled to Edinburgh, while writings from 1790 detailed "a period of great physical and creative activity for Burns", the team said.

The initial findings have been published in The Journal of the Royal College of Physicians of Edinburgh.

Moira Hansen, principal researcher on the project, 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 - and something that our project is properly studying for the first time.

"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.

"We have pinpointed evidence which showed bouts of increased energy and hyperactivity, and periods of depression and a withdrawal from day-to-day life.

"Further work to take account of the conventions of letter writing in the 18th century, who Burns was addressing his letters to and the different activities he was involved in at the various stages of his life is still being carried out.

"But we now believe Burns may have had what we would recognise today as bipolar disorder. We will carry out further in-depth analysis to create a mood map of his life to chart these highs and lows linking it to what was happening both in his private and public life to judge how it impacted on his writing."

Professor Daniel Smith, professor of Psychiatry at the University of Glasgow, hopes the findings can help to de-stigmatise psychiatric disorders.

He said: "Obviously it hasn't been an easy task given our subject has been dead for more than 200 years. We hope that the possibility that Scotland's national bard, a global icon, may have had bipolar disorder will contribute to discussions on the links between mental illness and creativity.

"This work might also help to de-stigmatise psychiatric disorders such as bipolar disorder and depression."

Professor Gerard Carruthers, co-director of the University's Centre for Robert Burns Studies, said: "Robert Burns was a complicated man, with an amazing catalogue of work produced in a short lifetime before he died at 37. Today he holds a fascination not just for Scots but a worldwide audience.

"The fact that Scotland's national bard may have had bipolar disorder is part of the telling and understanding of all aspects of the bard's story to reveal a more accurate picture of the real Robert Burns. "