Stroke patients prescribed a common antidepressant show no improvement compared with those given a dummy drug, a study has found.
Earlier research from France had suggested that taking the drug, called fluoxetine, might reduce disability after stroke.
The latest study found no difference between the improvement in physical ability of stroke patients who took fluoxetine for six months and those who took a placebo - an inactive substitute.
Experts stress that people already taking the drug should not stop without speaking to their doctor first.
Fluoxetine is a common type of antidepressant that includes the branded drugs Prozac and Prozep.
The University of Edinburgh-led study involved more than 3000 stroke patients at over 100 hospitals around the UK.
Half of the participants started taking fluoxetine daily within the first two weeks of their stroke, while the remainder took a placebo.
Those who took fluoxetine were less likely to develop depression, but, there was a small increase in bone fractures reported in this group.
Researchers say their findings do not support the use of fluoxetine to promote recovery after stroke in the UK.
The study, called FOCUS, is published in The Lancet and was funded by the Stroke Association and the National Institute for Health Research (NIHR). The findings are being announced at the UK Stroke Forum annual conference in Telford, UK.
Co-chief investigator Professor Gillian Mead, of the University of Edinburgh's Centre for Clinical Brain Sciences, said: "FOCUS has shown that there is no benefit in the routine prescription of fluoxetine to improve recovery after a stroke, contrary to the promising results of smaller trials.
"There are other reasons a patient may be prescribed fluoxetine and we do not recommend that people change their treatment regimen without first consulting with their doctor."
Fellow co-chief investigator Professor Martin Dennis, of the University of Edinburgh's Centre for Clinical Brain Sciences, said: "We have been working closely with researchers in Australia and Sweden who are running similar trials, the AFFINITY and EFFECTS trials. The results of those studies will reveal whether taking fluoxetine might offer benefits for stroke patients in other health systems."
Kate Holmes, Assistant Director of Research, Stroke Association said: "While this important study shows no reduction in disability after stroke, this is an incredibly challenging field of research. For the 1.2 million people currently living with the disabling and often devastating consequences of stroke, research to improve lives and reduce disability after stroke is of incredible value and importance. We look forward to hearing the outcomes of further trials in this area and hope that we will see some positive benefits for stroke survivors soon."