Remember Me: Use of Amnesia in Fiction

Heidi asks:

My question is, if I have a character that drowns but is revived, could they have temporary amnesia, especially if they hit their head? If so, how long might it last?  A few days? I know Goldie Hawn's character in Overboard gets amnesia after falling off a boat into the water, but I'm not sure how accurate that really is.

Dianna says:

The definition of drowning: A submersion event where a patient is pronounced dead within 24 hours of the event.

 If a patient dies 24 hours post the event, it's called a drowning-related death.

That said, your character did not drown and was then resuscitated. Instead, your character suffered a near-drowning event. In order for it to be referred to as a near-drowning event, the patient must be treated for at least one submersion-related complication. You say your character was resuscitated, so I'm assuming the patient was in cardiac arrest, which would definitely be considered a submersion-related complication.

Detail to consider: How long was the patient in cardiac arrest? In cold water, the mammalian diving reflex can prevent death, even after prolonged submersion (a patient in cardiac arrest can be resuscitated after 30 minutes or even longer).

I'd definitely write in that the character hit their head somehow and then suffered a prolonged cardiac arrest due to the submersion post hitting their head. (Basic background information: If the human body loses its oxygen supply, the heart stops. Since we can't breathe under water, we're unable to in-take oxygen.) If cold water isn't fitting for your story, then lower the cardiac arrest time to 5-10 minutes, which is still long. The amnesia could occur simply from the trauma to the head only. The near-drowning event and long cardiac arrest time could worsen the amnesia.         

Anterograde amnesia: Memory disorder only affecting the retention of new information and events. Example: Patient Jim can only identify his friends, recall their names, retell stories about them ONLY if he knew them BEFORE the amnesia. So, when Patient Jim meets anyone after suffering with amnesia, it doesn't matter how much time he spends with them, next time he sees that person he won't remember them at all.   

Retrograde amnesia -- Memory loss of the past or segments of the past.

Some patients can suffer with both anterograde and retrograde.

Some patients fully recover from amnesia, some don't.

Every patient is truly unique with every medical situation -- how one patient's body responds medically, another patient responds completely different. So, you could write whatever you want (within reason) with amnesia and it would be realistic. Again, every patient is very different.

In Overboard, that character's memory returned in a very realistic manner. What happened was she had a strong visual (her husband) of her past, which triggered her brain to remember her past, and pop her memory returned. Sometimes memory return is gradual, other times it comes all at once. However, the situation with her simply falling into the water and losing consciousness then coming to in the hospital with amnesia is over the top Hollywood. If I remember correctly, the storyline was that the cold water and the experience itself (floating in the ocean for hours), was the cause of amnesia.

Sure, it's possible (again, everyone is different) but not a solid storyline. To me, what that storyline says is the amnesia is an emotional issue (the floating experience, plus not being happy in her life), not a medical issue, which is definitely possible, but they should've highlighted that point. Or, adding in head trauma would've made it an even better story.   

The tricky thing about amnesia (but it's good for writers) is it deals with the brain, an organ us humans will never be able to truly understand like we do all other organs and systems, so we have little knowledge on how or why some things occur or don't occur with: memory, personality, personality disorders, mental illness, etc.