A new study is taking place in over 100 medical centers around the world that will attempt to determine whether or not a specific hormone could help the victims of traumatic brain injuries recover more successfully in the wake of their accident. Currently, there are no FDA-approved drugs to treat those with severe brain injuries.

The study was developed after researchers noted that women with traumatic brain injuries have much better outcomes than men who suffer similar injuries. Scientists now believe that women’s brain swell less after a head injury because of elevated levels of progesterone, a hormone associated with pregnancy and fertility in women (though the hormone is also present in men in smaller amounts).

More specifically, researchers hope that progesterone will protect cell membranes in the days after a traumatic brain injury, an action that some believe will prevent dangerous swelling from taking place. In many cases, brain damage is not just caused in the initial impact of an accident, but in the three days following the accident when the brain swells inside the skull, crushing itself.

The new study will look at the outcomes of 15 patients with serious head injuries at 100 hospitals around the world. Of the 150 patients, half will be given a placebo while half will be given the hormone. All patients will be evaluated six months after their accidents.

Each year an estimated 1.5 million people in the  United States suffer traumatic brain injuries.