Suicide risk similar across antidepressant types
The risk of suicidal behavior is not significantly greater with selective serotinin reuptake inhibitors (SSRIs) such as paroxetine than it is for the older tricyclic antidepressants, claim researchers.

"The relation between use of antidepressants, especially SSRIs, and suicidal ideation and behaviors has received considerable public attention recently," note Hershel Jick and colleagues from Boston University in Massachusetts, USA.

To determine whether concerns surrounding SSRIs are warranted, the team estimated the relative risks of nonfatal suicidal behavior associated with four antidepressant medications – the SSRIs fluoxetine and paroxetine, and the tricyclics amitriptyline and dothiepin – using the UK General Practice Research Database for 1993 to 1999.

In all, 159,810 patients starting treatment with one of these four antidepressants were identified, with data for 555 patients who showed suicidal behavior and 2062 individuals who did not used for the current study.

The results, published in the Journal of the American Medical Association, showed that the relative risks for newly diagnosed nonfatal suicidal behavior were similar for the four antidepressants, at 0.83 for amitriptyline, 1.16 for fluoxetine, and 1.29 for paroxetine compared with the reference drug dothiepin. This remained true even after taking into account confounding factors such as age, gender, time of year, and time from first antidepressant prescription.

The team discovered that the time since starting antidepressant treatment was strongly associated with the risk of suicide. The risk of nonfatal suicidal behavior during the first 9 days of antidepressant treatment was four times higher than the risk after at least 90 days of use, while the risk of fatal suicide during this early treatment period was increased by around 38-fold.

"We think the most likely explanation for this finding is that antidepressant treatment may not be immediately effective, so there is a higher risk of suicidal behavior in patients newly diagnosed and treated than in those who have been treated for longer," the researchers write.

However, they add: "We cannot exclude what we think is a less likely possibility, namely that the drug itself 'causes' depression to worsen rapidly, thus leading to suicidal behavior."

JAMA 2004; 292: 338-343