Scientists have discovered that repeated brain trauma, which commonly occurs in athletes, may affect behavior, mood and thinking abilities, according to a study published in the journal Neurology.

Researchers from the Boston University School of Medicine examined the brains of 36 deceased male athletes aged between 17 and 98 years.

All athletes had been diagnosed with chronic traumatic encephalopathy (CTE) following death. CTE is a brain disease linked to repeated brain trauma - most commonly found in athletes.

There were no other brain diseases found in the athletes, and the majority of them had played amateur or professional football, while others participated in hockey, wrestling or boxing.

The researchers also interviewed the families of the athletes to compile information about their life and medical history, including details of:

  • Dementia
  • Changes in thinking
  • Mood
  • Memory
  • Behavior
  • Motor skills
  • Ability to carry out daily tasks.

Cognitive decline and mood changes

The findings were that 22 of the athletes showed behavior and mood problems as their first symptoms of CTE, and 11 showed memory and thinking problems as the first symptoms. The other three athletes did not show any symptoms of CTE at the time of death.

Additionally, 91% of the athletes who showed symptoms of behavior and mood problems also experienced symptoms of memory and thinking decline at some point.

Of those who experienced memory and thinking problems, 55% showed changes in behavior throughout the disease, while 64% showed changes in mood.

The family members of the relatives reported that the athletes who experienced mood symptoms were more "explosive, out of control, physically verbal and violent, and depressed" compared with the athletes with memory and thinking problems.

In detail, of the athletes with mood symptoms:

  • 73% were described as explosive
  • 68% were physically violent
  • 64% were out of control
  • 74% were verbally violent
  • 86% were depressed.
The researchers conclude:

"This [research] suggests there are two major clinical presentations of CTE, one a behavior/mood variant and the other a cognitive variant."

The study authors add that the findings may also suggest that when diagnosing dementia in adults with a history of repeated brain trauma, the diagnosis may be inaccurate due to the similarity in the symptoms of both CTE and Alzheimer's disease.

The researchers warn that although this study is the largest to date to analyze the "clinical presentation and course of CTE in autopsy patients," the findings should be viewed with caution.

There was no comparison group of athletes without CTE involved in the study, and the number of overall cases in the study was small, meaning there could be more variation in CTE than the findings show.

Previous studies have supported the link between athletes and progressive brain disease. Other research from Boston University in 2012 revealed that contact sports consisting of years of blows to the head may be directly linked to brain damage, eventually leading to dementia.

A study from the University of California, Los Angeles this year revealed the development of a new PET scan that can identify CTE in living patients.