Louise Bradvik and Mats Berglund, from Lund University, Sweden, say that women who have tried to kill themselves several times in the past should be kept under suicide watch, as they have an increased risk of death in a future attempt.
For men, say the researchers, this increased risk reflects the severity of their previous attempts.
They came to the above conclusion after examining suicide attempts in 100 patients who committed suicide and in an age- and sex-matched control group, investigating the effects of age on suicidal behaviour, as a risk factor for accomplished suicide.
They studied the hospital records of patients admitted between 1956 and 1969 and followed up until 2006.
"Men and women showed different patterns of suicide attempts in the older age groups. The risk for an initial suicide attempt reduced with age in all females and in male controls, but not in male victims, repetition and severity then showing a special pattern," said Bradvik.
"Suicide attempt is known to be one of the main predictors for suicide in depression. If attempts are repeated or serious, the risk for suicide is considered to be increased. However, to our knowledge, there has been no investigation into the predictive value of age at repeated and severe suicide attempt for accomplished suicide. In our study it appears that from middle age onwards, repeated attempts are a risk factor for suicide in women and so are severe attempts for men," said Bradvik.
"In other words, though all suicide attempts should be taken seriously, an older woman who makes a repeated attempt is at higher risk for suicide and needs more observation and treatment than a young female repeater. Correspondingly, an older man who makes a severe attempt (or an initial attempt) is in need of more observation," he added.
The study focussed on patients with severe depression (with psychotic and melancholic features) only.
It is unknown if the findings are applicable for other depressives.
The study has been published in the open access journal BMC Psychiatry.