This chapter describes what happens after a concussion, from the immediate changes in neurochemistry to the signs and symptoms that may be present in the days, weeks, and months following the event. It discusses the neuropsychological effects, including cognitive, physical, emotional/mood, and sleep symptoms. This chapter also describes dangers signs, which could be indicative of a more serious brain injury. It explains possible long-term effects of concussion, including complications associated with multiple concussions, postconcussion syndrome, second impact syndrome, chronic traumatic encephalopathy (CTE), and suicide. Concussion symptoms provide clues related to what is going on in the child’s or adolescent’s brain. Concussions often go unreported because individuals are unaware that an injury has occurred. Some may also consider the injury not severe enough to warrant medical attention. In some cases, the effects of concussions are so intense, and individuals become so distraught, that they become suicidal.