The cartoon 'Finding Nemo' is one of the few films to accurately portray amnesia, researchers claim.
Dory, the blue tropical fish, shows the 'reality' of amnesia
They say the fishy tale, along with a few other honourable exceptions, such as 'Memento', stands out for showing the realities of the condition.
But the researchers, from the National Society for Epilepsy, say the majority of amnesiac plots bear no relation to medical reality.
The research is published in the British Medical Journal.
Amnesia has been a staple device of film plots since the days of the silent movie.
One of the first to use it was the 1915 film 'Garden of Lies', where a doctor hires a new husband for an amnesiac bride in an attempt to jog her memory.
Looking at numerous films that have appeared since, the researchers say most amnesic characters are unrealistically able to function as if on a 'clean slate'.
They suffer very few problems managing everyday tasks, while managing to hold down new jobs and function socially.
But in real life, amnesic patients do often experience significant difficulties in taking in new information, making many everyday tasks extremely difficult.
'Lost and profoundly confused'
One of the few movies to reflect this correctly is 2000's 'Memento', starring Guy Pearce, in which his character develops a severe anteretrograde amnesia, which means his long-term memory is intact, but he has no short term memory, and he cannot create new memories.
Writing in the BMJ, Dr Sallie Baxendale of the National Society for Epilepsy, said: "Unlike most films in this genre, this amnesiac character retains his identity, has little retrograde amnesia [where memories of the period just prior to the injury are lost] and shows several of the severe everyday memory difficulties associated with the disorder."
She also praised the portrayal of Dory in last year's 'Finding Nemo.
Dr Baxendale said the animated blue tropical fish has problems learning and retaining information, recalling names and knowing where she is going or why.
She said this was "an accurate portrayal of the considerable memory difficulties faced daily by people with profound amnesiac syndromes."
She added: "The frustration of the other fish around her with constant repetition also accurately reflects the feelings of people who live with amnesiac patients.
"Although her condition is played for laughs during the film, poignant aspects of her memory loss are also portrayed, when she is alone, lost and profoundly confused."
But most movie amnesiacs do not get such glowing reports from the researchers.
They highlight a number of failings:-
- Complete personality changes, - where 'bad' characters become 'good' with the onset of amnesia, as in the Goldie Hawn/Kurt Russell 1987 movie 'Overboard'.
In reality, amnesiacs' personalities are rarely affected,
- The 'blow to the head cure' - A myth, but seen in many films, perhaps most famously in the case of Tom the cat in Tom and Jerry,
Dr Baxendale said: "The medical profession cannot, and should not, dictate cinematic content.
"However, since movies both inform and reflect public opinion, the public seems to have very little understanding of amnesiac syndromes.
"Clinicians should be aware of this when talking to patients and their relatives."
A spokeswoman for the National Society for Epilepsy, said memory loss was one of the most common problems that affected people with epilepsy.
She added: "While research like this doesn't help people in these conditions in any medical way, it's important that we do look at how medical conditions in general are portrayed, especially those that may be portrayed in an off-beat way, so that we can try to counteract that by putting out correct and appropriate messages."