Traumatic memories that underlie symptoms of post traumatic stress disorder (PTSD), some depression and anxiety disorders are problematic to treat; their intense emotional content fixes them firmly in the memory.
However, researchers discovered that drugs called histone deacetylase inhibitors (HDACis) loosen the grip of traumatic memories, making them easier to release or replace. Using HDACis with exposure therapy may prove to be an effective treatment combination for traumatized individuals, as it was for some fearful laboratory mice.
About Exposure Therapy
Exposure-based psychotherapy is a common and sometimes effective treatment for anxiety-related symptoms. With a therapist’s support, people are exposed to the environments, thoughts, or memories that provoke their fear. Repeated exposure without further traumatic consequence may extinguish (erase/diminish) the individual’s distress. A counselor and client can also work to revise or replace troubling memories.
Exposure therapy is most effective when the triggering traumatic event happened recently. Older memories tend to be more stubborn, and sometimes refuse to be erased.
HDACis and Exposure Therapy
To test the effectiveness of HDACis, scientists exposed some heroic mice to a tone followed by an electric shock. As expected, the mice soon reacted with fear whenever they heard the tone, even if a shock were not given. Then, researchers gave exposure therapy to the traumatized mice by repeatedly playing the tone without applying a shock. They discovered:
- Exposure therapy worked with mice that had been traumatized by the tone and shock the day before.
- Exposure therapy did not help the mice who had been traumatized a month earlier (constant exposure to the tone—without a shock—did not diminish their fear response).
- Mice that were traumatized a month earlier were given HDACis, which activates genes involved with memory and learning. With exposure therapy, these mice learned not to freeze in fear upon hearing the tone; their fear response was extinguished.
“Collectively, our findings suggest that exposure-based therapy alone does not effectively weaken traumatic memories that were formed a long time ago, but the HDACis can be combined with exposure-based therapy to substantially improve treatment for the most enduring traumatic memories,” said researcher Li-Huei Tsai, Massachusetts Institute of Technology.
Source: Science Daily
