If you’ve seen Netflix’s “Senior Year,” then you know it centers around main character Stephanie Conway (Rebel Wilson), a former high school cheerleader who falls into a coma only to wake up 20 years later still craving the title of prom queen. In the movie, Wilson’s character remembers everything in her life as it was before the coma, almost as if her brain was frozen in time. But what actually happens to the brain during a coma is still not fully understood by the medical community. In fact, many of the realities of being comatose are overlooked in the film (like the fact that the coma lasted 20 years — that’s actually a pretty rare occurrence!).

Research into prevention and treatment techniques for comas is ongoing, and the chances of a person in a coma waking up or surviving depend heavily on the initial cause of the coma. Not to mention, as physically challenging as it is for the person experiencing the coma, loved ones also take on a “significant emotional burden,” studies say, as they transition to becoming caregivers and decision-makers for someone else’s health. Whether you’re caring for a loved one in a coma or just wondering what a coma truly is, here’s a primer on what you need to know about comas.

What Is a Coma, Actually? Signs and Causes

Simply put, a coma is “a state of unconsciousness” that occurs over a prolonged period of time, according to May Kim-Tenser, MD, a neurologist with Keck Medicine of USC. Signs of a coma include unresponsiveness to voice and to “painful stimuli, except for reflexes,” Dr. Kim-Tenser explains. People in a coma “are unaware of their surrounding environment.” Comas can be caused by a number of things, including:

• Traumatic brain injury
• Stroke
• Brain tumor
• Seizures
• Hypoglycemia or hyperglycemia (high or low blood sugar, respectively) from underlying diabetes
• An infection, such as encephalitis or meningitis
• Drugs or toxins

To prevent brain swelling, a person can also be put into a medically induced coma through the use of anesthetics after a severe injury.