Blackouts in humans are caused by traumas, substances and diseases, according to Better Medicine. A blackout is defined as a period of unconsciousness or memory loss, and it can be benign, serious or life threatening. Better Medicine recommends any unexplained blackouts be evaluated by a medical professional. Memories of what occurred during a blackout are sometimes recoverable. Repeated blackouts can cause difficulty with forming new memories.
According to Better Medicine, traumatic blackouts occur due to complications from brain surgery, concussions, electroshock therapy, bad reactions to inoculations, mild head injuries, phlebotomy (passing out when blood is drawn), and as a reaction to an emotional event. Substances that can cause blackouts include prescription medications. Blackouts are a possible side effect of seizure medication, cancer treatments or agents used in anesthesia. Poisons, recreational drugs, and alcohol abuse also lead to blackouts. Certain diseases can cause blackouts as a symptom. Anemia, many brain and spinal cord diseases, dementia, depression, and Parkinson's disease all can cause blackouts. More temporary conditions, such as dehydration and certain nutritional deficiencies, also cause blackouts. There are several life-threatening causes for blackouts that require immediate medical attention; blackouts caused by stroke, heart attack or a traumatic injury can be fatal.