By identifying common features in the letters, it would be possible to draw up a list of symptoms to help identify potential suicides.
Rory O'Connor of Queen's University, Belfast, told the British Psychological Society annual conference in Edinburgh: "The suicide notes are the closest you will get to the state of the person prior to their death."
He analysed 45 notes left by people who killed themselves in Northern Ireland in 1993-94.
Mr O'Connor was given special permission to look at the notes - which are usually kept confidential - for the study.
They varied considerably. Some people left just a few lines, while others wrote pages and pages to several people.
But in all of them, they indicated a sense of hopelessness and "an unbearable psychological pain".
Those who were clinically depressed - 29 out of the total - also felt out of control, were unable to look beyond their problems and acted illogically.
They felt let down because of failed relationships and thought life was not worth living.
People showing symptoms like these should be regarded as a suicide risk, he said, adding: "Having this list means that if a depressed person comes to me as a GP, then I will know what to look for."
He admitted, however, that it was more difficult to help someone who was not actually depressed although they went on to commit suicide.
Such people did not feel that their lives were out of control and were less likely to seek help for their condition, such as going to their doctor.
However, Mr O'Connor said it was still possible to help those people most likely to take their own lives - people who were depressed.
"You cannot eliminate the problem, but you can reduce the suicide rate," he said.Reuse content