How long does a sad movie leave you feeling blue? Remembering something sad can trigger emotions that persist long after the event itself has passed. But people with impaired memories seem to retain the emotion long after they have forgotten the emotionally charged event itself—longer, in fact, than people who can recall the incident well—according to a new study.

The findings, published online April 12 in Proceedings of the National Academy of Sciences, are some of the first to investigate the persistence of emotion after memory of the triggering incident has faded and reveal a need for more research about how people with faulty memories, such as the growing number of people with Alzheimer's disease, process and conserve emotions. 

Researchers at the University of Iowa worked with five patients who had severe amnesia due to damage in the hippocampus (which is thought to play a role in creating lasting memories), resulting in a condition that might be comparable to Alzheimer's and other forms of dementia. The team surveyed the patients' emotional states before, right after and 20 to 30 minutes after showing them a series of film clips of sad scenes (including a funeral in Steel Magnolias and dementia as portrayed in The Notebook) one day and happy scenes (such as practical jokes from the show America's Funniest Home Videos and a humorously faked orgasm in When Harry Met Sally) on another day.

The researchers, led by Justin Feinstein of Iowa's departments of Neurology and Psychology, found that even after memory tests (given five to 10 minutes after the film clips ended), the amnesic subjects remembered little—if any—of the details of what they had just seen, but retained the overall emotion for 20 to 30 minutes afterward. Although the subject group was small, the researchers concluded that the "findings provide direct evidence that a feeling of emotion can endure beyond the conscious recollection for the events that initially triggered the emotion," they reported.

Furthermore, when comparing the amnesic patients to normal controls who underwent the same viewing and questioning, the researchers found that the memory-impaired individuals felt happy about as long as their normal counterparts, but the amnesic patients' sadness persisted longer.

Feinstein and his colleagues noted that these findings challenge the idea that by minimizing a specific memory of past trauma, associated sadness will also decrease. One amnesic patient in particular explained that the sources of happy feelings were usually also mysterious, but she didn't feel the need to remember exactly what triggered them. Sad emotions, on the other hand, left her mentally searching for a cause, thereby, perhaps extending the duration of the feeling in comparison with a person who can remember what caused the sadness. "Erasing memories may have the paradoxical effect of actually prolonging (rather than alleviating) feelings of distress," the researchers explained.

The results might also provide more scientific "reasons for treating amnesic patients with respect and dignity," the researchers concluded. "A simple visit or telephone call…might have a lingering positive on a patient's affective state even though the patient may quickly forget the visit or phone call," they noted. Similarly, "routine neglect from staff at nursing homes may leave the patient feeling sad, frustrated and lonely" for extended periods as they try to figure out why they feel that way.

Image courtesy of iStockphoto/CREATISTA