According to the attorney for convicted murderer Aaron Hernandez, tests show the former NFL star had the brain disease CTE. CTE, or Chronic Traumatic Encephalopathy, is believed to stem from repeated hits to the head. But the disease is about more than just concussions.

CTE is a neurodegenerative brain disease. Symptoms are similar to those of another brain disease: Alzheimer’s, and can include memory loss, confusion, aggression,  rage and at times, suicidal behavior. Scientists say CTE may result from repeated hits to the head.

While the list of former football players diagnosed with CTE continues to grow — the disease affects other groups as well, such as soccer players,baseball players and possibly military veterans. The condition was first observed in boxers and described in a study in 1928. Those findings were published in the journal of the American Medical Association.

Scientists are still working to identify other risk factors for CTE. Researchers believe there may be environmental and genetic components to the disease. And the disease can only be diagnosed definitively after a person has died.

However if science advances, and researchers are able to identify CTE while people are alive, researchers believe they will be a step closer to finding a cure to this potentially deadly disease.