June 26 (UPI) -- Head injuries experienced while young may increase a person's risk for depression and dementia decades later, according to a study published Friday by the journal Neurology.
In general, those with a history of repetitive head impacts scored 1.24 points higher on a 15-point depression symptom scale than those without a history, the researchers found.
Study participants with a history of traumatic brain injury, or TBI, had scores up to 0.75 points higher, they said.
"The findings underscore that repetitive hits to the head, such as those from contact sport participation or physical abuse, might be associated with later-life symptoms of depression," study co-author Michael Alosco said in a press release.
"It should be made clear that this association is likely to be dependent on the dose or duration of repetitive head impacts and this information was not available for this study," said Alosco, associate professor of neurology at the Boston University School of Medicine.
BU researchers have focused on the long-term effects of chronic traumatic encephalopathy, or CTE, a brain condition seen by professional athletes in sports like football and hockey, and some in youth sports, who have experienced head impact-related injuries.
For the new study, Alosco and colleagues analyzed data on more than 13,000 adults aged 40 and older -- with an average age of 62 -- from the internet-based Brain Health Registry. Among participants, 725, or 5 percent, reported sustaining previous repetitive head impacts through contact sports, abuse or military service.
In all, 7,277 said they had experienced TBI, 2,604 with loss of consciousness.
Researchers measured depression symptoms among study participants using the Geriatric Depression Scale-15, and assessed cognitive function with CogState Brief Battery and Lumos Labs NeuroCognitive Performance Tests.
Overall, there was a dose-response-like pattern between head trauma and depression symptoms, the researchers said. Specifically, participants without any history of either TBI or repetitive head impacts had the fewest symptoms of depression, they said.
However, depression symptoms were highest for the groups who had a history of both repetitive head impacts and TBI, according to the researchers.
A similar cumulative effect was observed among those exposed to repetitive head impacts and TBI on tests of memory, learning, processing speed and reaction time, the researchers said.
Study participants with a history of repetitive head impacts or TBI had worse performance on some of the tests compared to those without any head trauma history. Those with both a history of repetitive head impacts and TBI with loss of consciousness had worse performance on almost all of these computerized cognitive tests, they said.
The findings were independent of age, sex, racial identity and education level, researchers said.
"It should be noted that not all people with a history of repetitive hits to the head will develop later-life problems with cognitive functioning and depression," said study co-author Robert Stern.
"However, results from this study provide further evidence that exposure to repetitive head impacts, such as through the routine play of tackle football, plays an important role in the development in these later-life cognitive and emotional problems," said Stern, director of clinical research at the BU CTE Center.