Stephen J.LurieMD, PhD, Senior EditorIndividualAuthorPhil B.FontanarosaMD, Executive Deputy EditorIndividualAuthor
To the Editor: Dr Williams and colleagues1 concluded that paroxetine showed moderate benefit
for depressive symptoms and mental health functioning in elderly patients
with dysthymia and more severely impaired elderly patients with minor depression.
We feel that this conclusion is more optimistic than would be suggested by
more precise expressions for the treatment effect, namely the absolute risk
reduction (ARR) and the number needed to treat (NNT).2
It is possible to calculate the NNT from the authors' Table 3, which shows
remission rates for patients attending 4 or more treatment sessions. For both
dysthymia and minor depression, 52 of 106 (49.1%) patients receiving paroxetine
reached remission, compared to 53 of 119 (44.5%) patients receiving placebo.
The ARR is therefore 4.6%. In other words, the individual patient has a 4.6%
chance of benefiting from paroxetine. However, the 95% confidence interval
(CI) of the ARR is –8.5% to 17.6%.3
The interval contains 0 and so it can be concluded that the ARR is not statistically
significant. Even the 90% CI does not reach significance (−6.6% to 15.5%).
The NNT is 100/4.6 = 21.7. This indicates that about 22 older patients with
minor depression or dysthymia need to be treated with paroxetine rather than
standard or placebo treatment for 1 additional patient to benefit after 11
weeks of treatment. The 95% CI of the NNT goes to infinity because 0 is part
of the 95% CI for the ARR. Thus, the 95% CI of the NNT (benefit) is 5.68 to
infinity and the NNT (harm) is 11.7 to infinity.4
Given the ARR and NNT with their 95% CIs, we believe that paroxetine did not
Terluin B, van Hout H. Treatment of Mild Depression in Elderly Patients. JAMA. 2000;284(23):2993-2994. doi:10.1001/jama.284.23.2993