Concussion occurs when a blow or impact to the head causes a sudden disruption to part of the brain known as the reticular activating system (RAS).

The RAS is located in the middle of your brain, and helps regulate your sense of awareness and consciousness. It also acts as a filter that allows you to ignore unimportant information by focusing on details you need.

For example, your RAS helps you to:

• fall asleep and wake up as required
• suddenly hear when your flight is being called in a noisy airport
• notice news items that interest you when you are quickly scanning a newspaper or news website

During a head injury severe enough to cause concussion, your brain is moved out of its normal position for a short time. This rotation disrupts the electrical activities of brain cells that make up the RAS, which in turn triggers symptoms associated with concussion, such as:

• loss of memory 
• a brief period of unconsciousness
• mental confusion

Increased risk

The three main causes of concussion are:

• being involved in a road accident
• an accidental trip or fall
• taking part in sporting or other recreational activities

Activities known to have a higher-than-average risk of concussion include:

• rugby
• football
• cycling
• boxing
• martial arts, such as karate or judo

Most doctors would argue that the physical benefits of regularly taking part in these sports outweigh any potential risks associated with concussion.

But this is only if you (or your child) wear appropriate equipment, such as a helmet, and are supervised by a suitably trained referee, umpire or trainer with experience of diagnosing and treating concussion.

The exception to this is boxing, as most doctors – especially those who treat head injuries – have stated that the risks of serious brain injury associated with boxing are unacceptably high and the sport should be made illegal.