Strenuous mental activity seems to delay recovery after a head injury, according to a new study published in Pediatrics .

Doctors have always recommended rest after a head injury, but it has never been clear how much to limit activities, what kind to limit (physical, mental, or both), and for how long.

Dr. William P. Meehan III, director of the Micheli Center for Sports Injury Prevention in Waltham, Massachusetts and his colleagues studied 335 patients (62% were males), aged 8 to 23 who came to a sports concussion clinic within three weeks of their injury between 2009 and 2011. Most of the concussions were sustained while playing ice hockey, football, basketball or soccer. The researchers asked them about their symptoms and how often they were reading, doing homework or playing games at each of their appointments.

Those with minimal cognitive activity were not reading or doing homework, and spent less than 20 minutes on the Internet or playing video games each day. They could have watched TV or movies or listened to music. Those with moderate or significant cognitive activity did some reading and some homework, but less than usual. Others had not limited their cognitive activities at all since their last clinic visit.

On average, patients took 43 days to fully recover from their concussions. Those with more minor concussions tended to get over their symptoms faster. So did those who did less with their brains while recovering.

Results showed that only those engaging in the highest levels of cognitive activity had a substantial increase in their symptom duration, while those at all lower activity levels seemed to recover at about the same pace.

According to Dr. Meehan, “This would suggest that while vigorous cognitive exertion is detrimental to recovery, milder levels of cognitive exertion do not seem to prolong recovery substantially”

In general, Meehan said, doctors recommend almost complete brain rest for three to five days after a concussion, followed by a gradual return to normal activities.

Athletes suspected of having a concussion should be seen by the most immediately available medical personnel, like an athletic trainer or team doctor, he said, with a follow-up visit to their primary care doctor.

I would also emphasize the importance of physical rest and complete avoidance of any activities that could result in another head injury before completely recovering from the first one. Complete recovery means no symptoms at all, including headaches, dizziness, mental fog, fatigue, difficulty concentrating, insomnia, anxiety, depression, and other. Taking a magnesium supplement can also help since animal studies show magnesium depletion following an injury. If rest alone does not lead to a complete recovery, cognitive behavioral therapy, medications (for anxiety, depression, and irritability), and Botox injections (for persistent headaches) are sometimes needed.