Sleep experts in quake-shaken Canterbury have backed the findings of a US study that has found sleeping after a traumatic event like an earthquake cements - and could even amplify - negative emotional memories.
In experiments by researchers from the University of Massachusetts, 106 young adults were showed images - some of which were disturbing - and rated their emotional responses to the pictures.
Half of the subjects then went to sleep, while the other stayed awake.
Twelve hours later, they rated the images again.
The results, published in the Journal of Neuroscience, showed that those who went to sleep had stronger emotional responses to the images.