Birth control pills are known to have many positive and negative effects. They can act as a contraceptive and help regulate, reduce, and alleviate bleeding and cramping on periods, depending on the type of pill and the dosage.  They can also prevent certain types of cancers. On the negative side, birth control pills do not protect you from sexually transmitted diseases (STD) or HIV, they have to be taken every day at the same time, and they may increase anxiety. They can also cause certain types of cancers.

Let’s start with the good news – studies have shown that birth control pills can prevent ovarian, colon, and endometrial cancer. According to the American Cancer Society, women who have been taking birth control pills for several years have a lower risk of developing ovarian cancer.

“Women who used oral contraceptives for 5 or more years have about a 50% lower risk of developing ovarian cancer compared with women who never used oral contraceptives,” the American Cancer Society said. “The benefit starts within 3 to 6 months after starting the pill. The longer you take it, the lower your risk.”

The longer the better is a reoccurring theme when it comes to birth control pills preventing cancer. The American Cancer Society says that birth controls pills containing both estrogen and progesterone can lower the risk of endometrial cancer, also known as uterine cancer (cancer in the lining of the uterus). They also say that the risk is lower even after being off the pill for a decade.

Birth control pills and their role in preventing colon cancer still needs further research but can be effective, according to the American Cancer Society. It is possible that the pill lowers the levels of some digestive chemicals in the body, which may prevent colon cancer.

Moving on to the not so good news – some birth control pills can actually increase some cancers, including breast and cervical cancer. Most birth control pills are made up of a combination of estrogen and progesterone. Progesterone, commonly known as the “pregnancy hormone,” tricks your body into thinking you are pregnant. The pill then combines it with estrogen because you are not pregnant and your body needs estrogen. Too much estrogen and progesterone, or too much of any hormone for that matter, can potentially cause cancer because it disrupts the natural cell cycle.

Women who have taken, or are taking, birth control pills are more likely to develop breast cancer than women who don’t. The research that has been done is not clear on what the exact cause is but it hints that too much estrogen and/or progesterone is the cause, according to the American Cancer Society. There are also other factors that increase the risk of breast cancer.

“Hormonal and reproductive history factors that increase the risk of breast cancer include factors that may allow breast tissue to be exposed to high levels of hormones for longer periods of time,” the National Cancer Institute (NIH) said.

These factors include menstruation starting at a young age, starting menopause at a later age, getting pregnant at a late age, and not having children.

The increased risk for cervical cancer is tied to HPV viruses and how it interacts with birth control pills.

“The hormones in oral contraceptives may change the susceptibility of cervical cells to HPV infection, affect their ability to clear the infection or make it easier for HPV infection to cause changes that progress to cervical cancer,” the NIH said.

The bright side – the increased risk fizzes out for breast and cervical cancers after a woman has stopped taking birth control pills for a long period of time.

The American Cancer Society notes that intrauterine devices (IUD) are forms of contraceptive that might reduce the risk of cancer more effectively.