Geographical variation in antipsychotic efficacy not ruled out


An individual patient data meta-analysis fails to exclude the possibility that atypical antipsychotics work better in patients from some parts of the world than others.

The analysis of data from 5233 patients with schizophrenia suggests that patients in North America may not respond as well as patients from Europe and the rest of the world.

These findings may indicate that “study results cannot be extrapolated from one geographical region to the others”, say study author Taina Mattila (Medicines Evaluation Board, Utrecht, the Netherlands) and co-workers.

They say that the variation found could be caused by differences in patient populations across the regions studied, particularly in age and ethnicity.

The differences between North America and other geographical regions did not quite attain statistical significance, but the authors say this could be due to much smaller patient numbers for the other regions. The raw data obtained for 22 of 29 studies that met the inclusion criteria included 3737 patients from North America, 1052 from Europe and just 444 from the rest of the world.

Pooled data for all five compounds studied showed an effect size of 0.368 for North America, with the prediction interval of 0.15–0.58 suggesting a small to moderate effect. But the potential effects were moderate to large in Europe and the rest of the world, with effect sizes of 0.564 and 0.530 and prediction intervals of 0.35–0.78 and 0.38–0.68, respectively.

Likewise, the odds ratios for response with an antipsychotic versus placebo were 1.71 for North America and 2.25 and 2.61 for Europe and the rest of the world, respectively.


I wonder how they controlled for other factors? One of the things that strikes me reading the boards here is how pervasive the use of cannabis is among Americans. Where I live it is so rare it is almost non-existent. Also drinking alcohol is very rare, so both of them are easy to avoid. I would have thought socio-cultural factors could be just as important - or more - than age and ethnicity.