Birth control shot Depo Provera impairs memory, reveals research from Arizona State University.
The ASU study connects medroxyprogesterone acetate (MPA), the hormone active in Depo Provera and many widely used menopausal hormone therapies, to impaired memory in rodents.
The U.S. Food and Drug Administration originally approved Depo Provera for use in October 1992.
It requires an injection every 12 weeks. Its 99 percent effectiveness and the infrequency of doses make the shot an attractive alternative for women seeking to avoid pregnancy.
While other studies have examined Depo Provera's effects on bone density,
The study led by Blair Braden, an ASU psychology doctoral student, and Heather Bimonte-Nelson, an ASU associate professor of psychology and director of the Bimonte-Nelson Memory and Aging Lab is the first to explore its effects on cognition.
The researchers note that other forms of hormonal contraception, such as the pill, do not use MPA.
The study used three groups of rats (which received doses at varying ages), plus a control group that did not receive the hormone.
"What we found was pretty shocking - animals that had been given the drug at any point in their life were memory impaired at middle age compared to animals that never had the drug," said Braden.
"We also confirmed that in the subjects that only received the drug when young, the hormone was no longer circulating during memory testing when older, showing it had cleared from the system yet still had effects on brain function," he stated.
Bimonte-Nelson added,"This research shows that even after this hormone is no longer on board, months and months later, resulting effects are impacting the brain and its function."
The study appeared in the journal Psychopharmacology.