Side effects from a single mild concussion are usually not permanent, states the American Association of Neurological Surgeons. However, a person who has had a mild concussion may suffer from symptoms such as memory loss, fatigue and dizziness for up to three months, says Healthline.
Post-concussive syndrome is diagnosed when a patient continues to exhibit at least three symptoms of a concussion after recovery from the head injury, says Healthline. Possible symptoms include headaches, insomnia and memory problems.
Although a single concussion should not cause long-term side effects, a second head injury shortly after the first concussion can cause permanent neurological damage, explains the American Association of Neurological Surgeons.