Teens and adults who participate in contact sports have substantially heightened chances of experiencing concussions and other forms of significant brain injury. In some individuals, brain injury leads to the onset of a progressively worsening form of brain degradation called chronic traumatic encephalopathy (CTE). In a study published in August 2013 in the journal Neurology, researchers from the Boston University School of Medicine assessed the potential effects of CTE in both teenage and adult athletes. The researchers found that the presence of CTE in these individuals can lead to meaningful declines in aspects of normal brain function related to memory and the ability to think clearly, as well as the ability to properly regulate mood and behavior. Concussion Basics Concussions belong to a group of brain injuries known as mild brain injuries (MBIs). However, the term \u201cmild\u201d does not refer to the potential consequences of these injuries; instead, it refers to the amount of force delivered to the head when these injuries occur. Even under the influence of relatively minor direct or indirect force, the brain can move in abnormal ways and make damaging contact with the interior surfaces of the skull. It can also twist in damaging ways without making direct skull contact. In either case, the result can be compression, stretching or rupture of brain cells in the affected area, or some other disruptive change in the distance that usually separates individual brain cells from each other. Chronic Traumatic Encephalopathy Basics Even a single concussion can significantly harm a person\u2019s normal short-term brain function. However, when concussions occur repeatedly over time, that person has ever-increasing chances of developing chronic traumatic encephalopathy, a condition that appears when a natural supportive protein in the brain\u2014called tau\u2014bunches up in abnormal clumps known as tau tangles. (These same tangles play a role in the onset and progression of the classic form of dementia called Alzheimer\u2019s disease.) At first, concussion-related tau tangles only form in limited areas of the brain. However, they eventually spread gradually throughout the brain\u2019s main nerve cells, interfere with those cells\u2019 ability to communicate and do their jobs, and subsequently trigger the decline in mental function that marks the presence of CTE. New Findings In the study published in Neurology, the Boston University School of Medicine researchers examined the impact of chronic traumatic encephalopathy on the mental function of 36 athletes between the ages of 17 and 98 who had participated in amateur or professional forms of contact sports such as football, boxing, wrestling or hockey. All of these athletes were free from other forms of brain disease, received a CTE diagnosis following their deaths and were assessed postmortem with the help of their medical histories and the recollections of their parents, wives or other close family members. After reviewing their findings, the study\u2019s authors concluded that 22 of the teens and men under examination had initially experienced symptoms of CTE-related mood and behavioral disruptions during life, while another 11 had initially experienced symptoms of CTE-related thought and memory impairment. Only three of deceased athletes showed no indication of their declining mental function while still alive. On average, the postmortem participants with CTE-related mood and behavioral disruptions showed symptoms of the disorder fully 24 years earlier than the postmortem participants with CTE-related thought and memory impairment. Generally speaking, the teen and adult athletes affected by mood and behavioral disruptions experienced more severe and dramatic symptoms than their counterparts affected by thought and memory impairment. For instance, compared to their thought- and memory-altered peers, the mood- and behavior-altered individuals had much higher chances of displaying intense forms of anger, periodically losing their emotional composure, participating in some form of verbal violence, participating in some form of physical violence and experiencing symptoms of depression. More than 90 percent of the athletes with mood and behavioral disruptions also experienced substantial thought and memory impairment, while only 64 percent of the athletes with thought and memory impairment also experienced substantial mood and behavioral disruptions. Considerations The authors of the study in Neurology note the fact that their assessments did not include a comparison group of athletes unaffected by chronic traumatic encephalopathy. While this fact does not invalidate their work, benchmark scientific studies almost always include a comparison group for balance and perspective. In addition, the authors emphasize the fact that their study only included a small number of athletes. While the overwhelming number of participants affected by CTE speaks directly to the potential consequences of playing contact sports, it\u2019s possible that this small sample size could produce an exaggeration of the average severity of CTE symptoms found in larger groups of affected individuals across the U.S.