March 12, 2010 -- SSRI antidepressants raise the risk of cataracts by about 15% -- enough to cause 22,000 extra cataract cases in the U.S. each year, Canadian researchers suggest.
But these widely prescribed drugs may pose a vision risk in elderly patients, suggest Mahyar Etminan, PharmD, and colleagues of the University of British Columbia, Vancouver, Canada.
"This study showed for the first time that SSRI use may be associated with an increase in the risk of cataracts," Etminan and colleagues conclude.
The researchers analyzed data collected from 18,784 cataract patients and 187,840 comparison patients between 1995 and 2004. All of the patients had heart disease and had undergone treatment for blocked arteries. Their average age was 73.
Only patients currently using antidepressants -- not those who had taken them in the past and stopped -- were at increased risk of cataracts. Even so, only 8.5% of cataract patients in the study had taken SSRI antidepressants at any time.
Not all SSRI antidepressants were found to increase cataract risk, although this may be because not enough people in the study were taking them for the researchers to detect a risk. Risk was found for three different antidepressants:
- Luvox raised cataract risk by 39%.
- Effexor raised cataract risk by 33%.
- Paxil raised cataract risk by 23%.
- Overall, use of any SSRI antidepressant raised cataract risk by 15%.
Assuming that 10% of Americans take SSRIs, that the increased risk is 15%, and that 1.5% of cataracts in the U.S. are caused by antidepressants, the researchers calculate that SSRIs may cause 22,000 extra cases of cataracts each year.
How Antidepressants Might Cause Cataracts
How could antidepressants cause cataracts?
SSRI antidepressants work by increasing the amount of serotonin in the brain. (Effexor is not strictly an SSRI, as it boosts norepinephrine as well as serotonin.)
Etminan and colleagues note that the lens of the eye has serotonin receptors -- switches that activate cellular functions. Animal studies show that serotonin can make the lens of the eye more opaque and lead to cataracts.
If the Etminan findings are confirmed, SSRI antidepressants would not be the first drug to increase cataract risk. Oral and inhaled steroids and beta-blockers have also been linked to cataract formation.
The Etminan study appears in the March 7 online issue of Ophthalmology. Pfizer, the maker of Effexor, and Abbott, the maker of Luvox, were contacted for comment but were unable to reply in time for publication.