New research finds that obesity and birth control pills may contribute to the development of multiple sclerosis (MS), illuminating a set of previously unknown factors that may account for a rising rate of diagnosis among women.

The findings are split over two separate studies conducted by the Raúl Carrera Institute for Neurological Research in Buenos Aires and Kaiser Permanente Southern California, respectively. Both papers were presented at the annual meeting of the American Academy of Neurology.

Dr. Jorge Correale, a researcher at Raúl Carrera and lead author of the obesity study, said in a press release that the link between a high BMI and MS may stem from a proliferation of the hormone leptin. "Leptin promotes inflammatory responses in the body, which could potentially explain the link between obesity and MS," he said.

To investigate, Correale and colleague surveyed data from 210 people with MS and 210 people without MS of the same sex in the same age cohort. They compared each participant’s BMI at the time of the study with her BMI at ages 15 and 20. The researchers found that, compared to non-obese people, people who are obese at age 20 are twice as likely to develop MS .

A similar link was found between MS and birth control pills. In this study, Dr. Kerstin Hellwig and colleagues looked at data from 305 women who had been diagnosed with MS or the precursor clinically isolated syndrome. This sample was then compared to 3,050 women who did not have MS.

Twenty-nine percent of the MS participants had used hormonal contraceptives for at least three months over the three years preceding the onset of symptoms.  The researchers found that women on birth control were 35 percent more likely to develop MS compared to women who did not use the pills. "These findings suggest that using hormonal contraceptives may be contributing at least in part to the rise in the rate of MS among women," Hellwig said.

MS is characterized by a gradual erosion of myelin — a protective sheath that protects your nerves. Damage is associated with a range of neurological problems, including numbness, blurred vision, tremor, and slurred speech. People living with the chronic disease may also develop muscle spasms, paralysis, and epilepsy.

The study dovetails with a number of recent attempts to improve prevention and screening for the condition. Last week, researchers at Technical University in Germany announced a new test that may catch the disease years before symptoms develop. Similarly, a 2013 study from Johns Hopkins University found that vitamin D blocks all symptoms of MS in mouse models of the disease.