The use of antidepressants is likely to account for only 10 per cent of the fall in suicide rates among middle aged and older people, suggests a large study in the Journal of Epidemiology and Community Health.
Globally, more than 800, 000 people commit suicide every year.
Rates have been falling in many countries, a factor that has been associated with better recognition of depression and the increasing use of antidepressants, particularly the newer selective serotonin reuptake inhibitors (SSRIs).
But research involving more than 2 million Danes aged 50 and above and living in Denmark between 1996 and 2000, throws this into question.
The researchers assessed changes in the numbers of middle aged and older people committing suicide during this period and the types of antidepressant drugs they had been prescribed.
Only one in five of those committing suicide was actually taking antidepressants at the time of death.
Suicide rates in older men fell by almost 10 per 100, 000 of the population during this timeframe, but among recipients of antidepressants, the fall was less than one.
For older women, only 0.4 of the 3.3 fall per 100, 000 of the population was accounted for by those being treated with antidepressants.
Overall, treatment type made little difference, although rates among men taking SSRIs were slightly higher than among those taking tricyclics.
Suicide rates were five to six times higher among those taking antidepressants than those who were not.
Previous Scandinavian and US research has suggested that a fivefold increase in the use of antidepressants could lead to a 25% decrease in suicide rates, with SSRIs having saved as many as upwards of 33, 000 lives, say the authors.
Sales of antidepressants in Denmark have soared from 8.4 per 1000 of the population in 1990 to 52.2 in 2000.
And suicide rates among older people have more than halved from 52.2 in 1980 to 22.1 per 100, 000 of the population in 2000.
The authors conclude that current antidepressant treatment accounts for only a fraction of the falls in suicide rates among older people.
But they nevertheless suggest that more should be done to pick up and treat depression among older people.