By Maria Cendejas

A new study finds that young women on birth control pills have a tendency to have less painful menstrual periods than those who are not on the pill, according to Reuters.

Swedish researchers found that of 2,100 women who were followed from the age of 19-24, those on the birth control pill had less severe pain over time.

It's already common that doctors to recommend the pill to women that have dysmenorrhea which is menstrual cramps and back pain. 

The birth control pills are not particularly approved for that purpose, but doctors can prescribe them for dysmenorrhea on an "off-label" basis. However, it hasn’t been clear how effective the pills are against period pain.

The new findings are not certain.

Dr. Ingela Lindh of Gothenburg University in Sweden, who led the study said, "Our study provides evidence for the effective relief of painful periods with combined oral contraceptives."

Both Lindh and one co-researcher have financial ties to companies that make birth control pills, the new research wasn’t supported by drugmakers though.

Menstrual pains typically fade as they get older, and they often lessen after they have a child. But even when age and childbirth were taken into account, the women who used the pill had less painful periods in the new study.

The study was published in the journal of Human Reproduction, and it doesn’t prove that the pill will alleviate dysmenorrhea.

It was an observational study that looked at the relationship between usage of the pill in women and dysmenorrhea risk. People in the clinical trials were randomly assigned to take a drug and were considered as the "gold standard" for proving cause-and-effect.

In 2009, a review of 10 clinical trials concluded that there was "little evidence" that the birth control pill improved any menstrual pain.

The trials are still in review and conclusions varied from one study to another depending upon in their methods and quality.  So it's hard to draw a firm conclusion, said Dr. Michele Curtis of the University of Texas Medical School at Houston, who wasn’t involved in the current study.

She told Reuters that the new study isn't exact, but "makes a strong case" that the pill is effective against menstrual pain.

"I think combined oral contraceptives really do help women with primary dysmenorrhea," said Curtis, who has received speaking fees from drugmaker GlaxoSmithKline, according to ProPublica's database Dollars for Docs.

A weakness of the current study is that it did not determine whether women had primary or secondary dysmenorrhea.  In some cases of secondary dysmenorrheal, birth control pills might help, but in others they will do nothing, Curtis said.

The study included 3 groups of women that were 19 years old in either 1981, 1991 or 2001. They filled out a standard questionnaire on menstrual symptoms, and then they repeated the survey in 5 years.

The study found Dysmenorrhea was common in the 1981 group, 37%t had at least moderate menstrual pain that disrupted their daily activities; in the 2001 group it was 47%.

But the pill users had less pain over the next 5 years. In general, the pill use was linked to a reduction of 0.3 units on the pain scale. This means that every 3rd woman on the pill went from severe pain to moderate pain, according to Lindh.

The researchers also looked at subgroups of women who were using the Pill at the age of 19, but not at age 24. On average, their menstrual pain increased over time. In contrast, pain decreased among women who were not on the Pill at age 19, but were at age 24.

There are biological reasons that the pill would help with dysmenorrhea, both Lindh and Curtis said.

Menstruation causes increased muscle activity in the uterus, which lessens blood flow to the uterus. And that's believed to be the root of menstrual pain.

Hormone-like compounds called prostaglandins help churn up that extra muscle activity. Since birth control pills lower the body's prostaglandin production, Lindh explained, it makes sense that they would ease dysmenorrhea.

Birth control pills cost anywhere from $15-$50 a month, and it isn’t the only treatment for dysmenorrhea.

Some women can find enough relief from nonsteroidal anti-inflammatory drugs, like ibuprofen and naproxen.

"Clearly, our evidence base is smaller for those things, and if a woman doesn’t want birth control or nonsteroidal anti-inflammatory drug, she could try an alternative,” said Curtis.

Birth control pills can have side effects like breast tenderness, nausea and vomiting, and spotting between periods. 

Most women with primary dysmenorrhea are younger. In fact, Curtis said, if you start having painful periods for the first time when you are 30, it's unlikely that it's primary dysmenorrhea. A secondary cause is probably at work.

The new study was funded by grants from the Gothenburg Medical Society and other groups.

Birth control pills often contain hormones, which increase risk for breast cancer.