Regardless, a traumatic event is an event where something so distressing occurs that the mind chooses to forget rather than deal with the stress. A common example of amnesia that is caused by traumatic events is dissociative amnesia, which occurs when the person forgets an event that has deeply disturbed them. An example would be a person forgetting a fatal and graphic car accident involving their loved ones. Physical deficiencies are different from head trauma because physical deficiencies lean more toward passive physical issues. Examples of physical deficiencies include Alzheimers disease, neurological paraneoplastic syndromes such as anti-NMDA receptor encephalitis, and vitamin B12 deficiency.Among specific causes of amnesia are the following:

Electroconvulsive therapy in which seizures are electrically induced in patients for therapeutic effect can have acute effects including both retrograde and anterograde amnesia. Alcohol can both cause blackouts and have deleterious effects on memory formation. Diagnosis
Types
Anterograde amnesia is the inability to create new memories due to brain damage, while long-term memories from before the event remain intact. The brain damage can be caused by the effects of long-term alcoholism, severe malnutrition, stroke, head trauma, encephalitis, surgery, Wernicke–Korsakoff syndrome, cerebrovascular events, anoxia or other trauma. The two brain regions related with this condition are medial temporal lobe and medial diencephalon. Anterograde amnesia cannot be treated with pharmacological methods due to neuronal loss. However, treatment exists in educating patients to define their daily routines and after several steps they begin to benefit from their procedural memory.
To him, he felt that he had just come to consciousness for the first time every time he was unable to hold on to information. This case also can be used as evidence that there are different memory systems for declarative and non-declarative memory. This case was more evidence that the hippocampus is an important part of the brain in remembering past events and that declarative and non-declarative memories have different processes in different parts of the brain. Patient R.B. Patient R.B. was a normally functioning man until the age of 52. At age 50, he had been diagnosed with angina and had surgery for heart problems on two occasions. After an ischemic episode (reduction of blood to the brain) that was caused from a heart bypass surgery, R.B. demonstrated a loss of anterograde memory, but almost no loss of retrograde memory, with the exception of a couple of years before his surgery, and presented no sign of any other cognitive impairment. It wasnt until after his death that researchers had the chance to examine his brain, when they found his lesions were restricted to the CA1 portion of the hippocampus. This case study led to important research involving the role of the hippocampus and the function of memory. Patient G.D. Patient G.D. was a white male born in 1940 who served in the Navy. He was diagnosed with chronic kidney failure and received hemodialysis treatment for the rest of his life. In 1983, he went to the hospital for elective parathyroidectomy.