DRUGS that help extinguish bad memories could offer new hope to people traumatised by terrifying experiences, research suggests.
Scientists believe compounds called histone deacetylase inhibitors (HDACis) allow the brain to "override" entrenched disturbing recollections with new non-threatening memories.
They hope the drugs, so far only tested on mice, can be used to clear away frightening memories that are anchored too firmly to be dislodged by conventional therapy.
The aim is to develop new treatments for post-traumatic stress disorder (PTSD), which affects a third of people who have had a traumatic experience such as military combat, a violent attack, or being involved in a major road accident or disaster. In severe cases, it can seriously erode quality of life.
A common form of psychotherapy treatment involves helping sufferers "re-live" their traumatic memory under controlled conditions. This process, known as exposure-based therapy, opens a short window that allows the memory to be disrupted and replaced by new memories.
However, while effective after a recent event, it tends not to work for older, more entrenched traumatic memories.
The new research suggests that HDACis makes the brain more malleable, enabling even deep-rooted traumatic memories to be extinguished by exposure-based therapy.
"Psychotherapy is often used for treating PTSD, but it doesn't always work, especially when the traumatic events occurred many years earlier," said lead scientist Dr Li-Huei Tsai, from the Massachusetts Institute of Technology in Cambridge, US.
"This study provides a mechanism explaining why old memories are difficult to extinguish and shows that HDACis can facilitate psychotherapy to treat anxiety disorders such as PTSD."