The research found that a mono infection during teenage years may be correlated with a MS diagnosis after the age 20
Multiple Sclerosis
Multiple Sclerosis
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More than 2.3 million people worldwide are living with a multiple sclerosis diagnosis — and new research reveals that developing the disease may be linked to contracting mononucleosis (a.k.a. mono or the "kissing disease") in childhood or adolescence.

According to the study, published earlier this month in the journal JAMA Network Open, scientists in Sweden and the United Kingdom discovered the correlation using data from nearly 2.5 million Swedish people. The research found that a mono infection during teenage years may be correlated with a MS diagnosis after the age of 20.

Researchers also noted that the risk of being diagnosed with MS decreases the older a person is when she or he contracts mono.

The population-based study used the Swedish Total Population Register to identity individuals born between Jan. 1, 1958 to Dec. 31, 1994, who reached 25 years old from Jan. 1, 1990, to Dec. 31, 2019. Participants were followed up with after every 15 years from 1978 to 2018.

To create accurate findings, researchers also factored in participants' sex, birth order, parents' age at birth as well as an MS diagnosis in a parent. Scientists also took into account the health of the individual's siblings.

Of the 2,492,980 participants evaluated, 5,867 had an MS diagnosis after reaching 20 years old, the study found. The median age of diagnosis was discovered to be 31.

"There were associations observed between infectious mononucleosis in childhood and adolescence and an increased risk for an MS diagnosis. This association remained significant after controlling for shared familial factors," the authors wrote in the study.

Researchers think the age range may reflect "variation in susceptibility to environmental exposures due to developmental changes of the immune system and [central nervous system]."

MS is disease of the immune system that eats away at the protective covering of nerves. It can disable the brain and spinal cord. Symptoms include: numbness, tremor or lack of coordination.

As for mono — the contagious infection is transmitted by saliva and caused by the herpes virus Epstein-Barr, and symptoms include: fatigue, rash, fever, and swollen glands. At least one out of four teenagers and young adults who get infected with EBV will develop infectious mononucleosis, according to the CDC.