Many women find the birth control shot Depo-Provera appealing because they don’t have to remember to take a pill every day. But ironically, recent research from Arizona State University suggests that it may contribute to memory loss down the line.

The researchers who conducted the study, published in the journal Psychopharmacology, injected rats with Depo-Provera and studied their cognition and behavior during the course of two months.

The study found that as they aged, rats that had been exposed to the shot performed significantly worse on cognition tests than those who did not. Researchers suspect that the hormone ingredient medroxyprogesterone acetate, which is often given to menopausal women, is responsible for the rats’ memory loss.

“The study suggests Depo-Provera could be associated with long-lasting memory impairment, even after treatment has stopped,” said Brittany Blair Braden, co-author of the study.

Pfizer, the company that creates the drug, declined to comment on the study.

Study co-author Laszlo Prokai, a biochemistry professor at the University of North Texas, said the test results merrited concern, although he cannot officially comment on the drug’s effect on humans.

“I believe these findings are the tip of the iceberg because any kind of synthetic drug product carries side effects,” Prokai said.

Depo-Provera’s side effects include abnormal bleeding, spotting and appetite changes. It is also suspected of lowering bone density, said Kai Tao, vice president of clinical operations at Planned Parenthood of Illinois.

Patients need to receive only four shots per year. The drug can benefit women with heavy periods, which makes it an attractive choice for patients, Tao said.

“Depo is probably one of the most popular forms of birth control because it requires little to do,” Tao said. “And it’s 99 percent effective, making it one of the most reliable forms of birth control.”

Despite its effectiveness, data from the Centers for Disease Control and Prevention suggest dissatisfaction among users. Twenty-two percent of women ages 15–44 have used Depo-Provera at some point, but only 2 percent still use it. According to the CDC website, 75.5 percent of women who discontinued use cited side effects as their reason for stopping.

“I do not believe that women are informed enough about side effects prior to receiving the shot,” Prokai said. “Even the doctors are not informed enough.”

But Tao said Planned Parenthood provides women interested in Depo-Provera with a detailed fact sheet to read and sign before receiving injections and requires them to speak to a staff member about possible side effects.

Tao did not find the study results significant enough for concern and said she would still recommend the birth control shot to most women of reproductive age.

“The study might be interesting to read, but I wouldn’t bring this up to my patients,” Tao said. “The results don’t tell me anything at all.”

Prokai said he believes that it is important to research Depo Provera because so many women have used it. He and his colleagues plan to do additional research so they can gather more conclusive results.

“Our future goal is to understand why Depo-Provera is associated with memory loss,” Braden said. “Then hopefully we can find a hormone that provides effective birth control without causing memory loss.”