According to a new Danish study published in the British Journal of Clinical Pharmacology, glioma, a rare form of brain cancer, may be an uncommon side effect caused by long-term use of hormonal contraceptives like the pill.

The glioma study’s leader, Dr. David Gaist, stated that the research suggests women under the age of 50 diagnosed with glioma “were 90 percent more likely to have been using hormonal contraceptives for five years or more, compared with women from the general population with no history of brain tumor.” This is not the first time hormonal contraceptives have been linked to certain neurological birth control side effects, but this new suggestion that they can cause a rare form of brain cancer is startling.

The researchers in this Danish birth control study did not go so far as to say that they had proven a cause-and-effect correlation, and Dr. Gaist emphasized that glioma is still very rare. Only five out of every 100,000 Danish women under the age of 50 develop glioma each year, which includes women taking contraceptive products like the birth control pill, according to Dr. Gaist’s study.

The study looked at Danish government data on women who had developed glioma over a ten year period. Researchers observed 317 cases of women who had developed glioma, of which 60 percent had used a hormonal contraceptive at some point in their life. The results were then compared to 2,100 glioma-free women of similar age ranges, half of whom had used some type of birth control drug or contraceptive device.

The study found that ultimately, use of hormonal birth control like the pill seemed to increase the risk of glioma and the risk increased even more with an increased duration of use. Women who used some type of hormonal birth control for less than a year were found to have a 40 percent greater risk of developing glioma when compared to non-users, while those who had used hormonal birth control for five years or more saw their glioma risk double when compared to non-hormonal birth control users.

This is not the first time birth control has been linked with potential side effects affecting the brain. In fact, many forms of hormonal birth control have recently come under fire for allegedly causing some women to suffer from pseudotumor cerebri (PTC).

What is Pseudotumor Cerebri?

Pseudotumor cerebri (or intracranial hypertension) is a painful neurological condition that causes increased brain pressure, mimicking symptoms of a brain tumor. Although researchers are still searching for the exact causes of PTC, many hypothesize that hormonal birth control products may increase a woman’s risk of developing the neurological condition because the products may cause poor absorption of cerebrospinal fluid.

Based on recorded PTC cases, some intracranial hypertension symptoms exhibited by birth control consumers include:

• Frequent headaches or migraines that start behind the eyes and increase in intensity with eye movement
• Pulsatile tinnitus
• Dizziness or Nausea
• Vomiting
• Blurred vision, double vision, blind spots
• Vision loss in one or both eyes
• Difficulty seeing to the side (Decreased peripheral vision)
• Seeing light flashes (photopsia)
• Neck stiffness
• Neck, shoulder or back pain
• Problems walking
• Forgetfulness
• Depression

As a result of the pain and suffering experienced by intracranial hypertension victims, many individuals have filed pseudotumor cerebri lawsuits or joined pseudotumor cerebri class action lawsuits against the manufacturers of numerous forms of birth control.