Even experts are stumped by multiple sclerosis (MS), the tricky autoimmune disease that affects women two to three times more often than men. To add to the confusion, there’s no diagnostic test for the disease, and one patient can experience wildly different symptoms from another.

What experts do know? MS occurs when the body starts to attack its own central nervous system, and certain factors can raise one’s risk of developing the disease.

Watch the video to learn about the five traits that might raise your risk of MS.

Don’t have time to watch? Read the full transcript:

Smoking: Smokers and ex-smokers are more likely to get MS than people who never smoked, and the more cigarettes you’ve had, the greater your chances of a diagnosis.

Age: You can be diagnosed with MS at almost any time, but it's most likely to strike from age 20 to 50.

RELATED: Top 10 Myths About Multiple Sclerosis

Low vitamin D: Our bodies produce D in response to sunlight, so people who live closer to the earth's poles are more likely to get MS than those who live closer to the equator.

You have another autoimmune condition: Autoimmune diseases tend to cluster, so if you have one, you may develop others.

Gender: The disease is much more common in women, research shows.