Commonly-prescribed antidepressants such as Prozac may not work as well or work at all when people also take anti-inflammatory drugs such as aspirin, ibuprofen or naproxen. This observation comes from a study at Rockefeller University that tested the effects of both drug types in mice and also looked at patient medical records. The findings are particularly meaningful for elderly patients who are being treated for depression, but who may also be on painkillers for arthritis.

The findings suggest that people who weren't helped by taking an SSRI and who were also taking aspirin or ibuprofen while on SSRIs might want to give the antidepressant another try, this time without taking the anti-inflammatory medication.

The study found that the changes in mouse behavior that occur when they are given an antidepressant were lessened when they were also given an anti-inflammatory drug. More importantly, it also found from medical records that the success rate among patients taking an antidepressant fell from 54% to 40% when they were also taking an anti-inflammatory drug.

The patient records came from the STAR*D trial, whose initial results were published in 2006. STAR*D assessed the effectiveness of various depression treatments in patients diagnosed with major depressive disorder. It looked at 4,041 patients over a seven year-period.

The Rockefeller study looked at the effectiveness of a single class of antidepressants known as SSRIs (selective serotonin reuptake inhibitors), which includes Prozac. SSRIs are often prescribed for depression, anxiety and obsessive-compulsive disorder.

The findings suggest that people who weren't helped by taking an SSRI and who were also taking aspirin or ibuprofen while on SSRIs might want to give the antidepressant another try, this time without taking the anti-inflammatory medication.

This may pose a problem for people who have arthritis or other painful conditions, most commonly the elderly. But it suggests that the possibility of temporarily eliminating anti-inflammatories at least be looked at.

"Many elderly individuals suffering from depression also have arthritic or related diseases and as a consequence are taking both antidepressant and anti-inflammatory medications. Our results suggest that physicians should carefully balance the advantages and disadvantages of continuing anti-inflammatory therapy in patients being treated with antidepressant medications," said Paul Greengard, PhD, Professor and director of the Fisher Center for Alzheimer's Disease Research at Rockefeller in a university press release.

The results also suggest that if doctors and psychiatrists inform their patients of the interaction of aspirin and ibuprofen when they are prescribing an SSRI, they could help ensure that patients get the full benefit of the SSRI.

An early online version of an article detailing the study was published by Proceedings of the National Academy of Science (PNAS) on April 25, 2011. The article will appear in a future print edition of the journal.