What could have caused the death of a twenty one years old football player?

A U Penn football player has committed suicide and had left his family and friends in a big confusion. Thomas was known by his friends as a normal and happy person who had lot of great opportunities in the future; yet, he chose to kill himself. Researchers from Boston University said that Thomas had chronic traumatic encephalopathy; it his makes him the first active college football player known to have had this disease. Its effects are basically neurobehavioral which include: poor decision-making, use of drugs and alcohol, depression and suicide, impaired memory, erratic behavior. CTE (chronic traumatic encephalopathy) has been identified in the brains of late NFL football players John Grimsley, Mike Webster, Andre Waters, Justin Strzelczyk, Terry Long, Tom McHale and Chris Henry. So, this leads the reader to conclude that no one is exempted from any kind of disease because only boxers get this disease.
This article has to do with science because it is related to the brain. The study of the brain is part of the biology job. This article is related to Biology. Also, this article refers back to research; which means that it involves some mathematical operations, and some physics tools as well as some chemistry knowledge. So, this article encompasses Biology, Mathematics, Chemistry, and Physics.
This concerns me because it has to do with the brain and I would like to be a brain surgeon and I would like to attend U Penn. So, being aware of the environment where I would spend my college life is a great thing.

http://www.cnn.com/2010/HEALTH/09/14/thomas.football.brain/index.html