An arm or light elbow to the head in bed or brushing the door post in the car or these other light impacts like noted by DeanBJJ do not cause inflammation. The anxiety is the cause of the inflammation.

Anxiety and inflammation: What is the link?


The impact forces of the light bumps is no more that routine head movements. Walking, especially walking down steps is more G force than these light bumps. The tactile sensation of the head contact triggers the anxiety response that causes the inflammatory response.

Exposure therapy with frequent expected and unexpected head contact can help reduce the trigger response.