The new research involved over 500 participants as part of more than a dozen previously released studies.
As part of a randomized clinical trial, assessing the effectiveness of either melatonin or the placebo occurred after 28 days of treatment.
"Having a TBI doesn't definitively equate with getting Parkinson's. The risk is still pretty small."
People who suffer brain injuries are at increased risk of dementia later in life, a large study suggests.