People suffering from post-traumatic stress disorder, or PTSD, may eventually be helped by a low-cost antibiotic. Early studies show the drug, doxycycline, may be beneficial in the treatment of the psychiatric condition.
People who have lived through a traumatic experience like war, natural disaster or rape will sometimes relive the experience in their minds to a disabling degree. They experience hyper-vigilance, flashbacks and nightmares.
Psychological therapy is usually the treatment of choice to ease the symptoms.
Now, scientists think they may be on to something else that works, an antibiotic called doxycycline. It is an old, extremely cheap drug that is normally used to fight bacterial infections.
Here's how it works: To form memories, studies have shown that our brains need proteins called matrix enzymes. They are found all over the body and when they're overactive they contribute to some immune diseases, even some cancers.
Drugs, including doxycycline, block these enzymes. Because of their association with memories, researchers wondered if the antibiotic might also weaken the mechanism that forms negative memories.
For a memory to persist, according to Dr. Dominik Bach, it has to be reconsolidated or altered in some way.
A clinical psychiatry researcher at University of Zurich and the Institute of Neurology at University College London, Bach has been conducting experiments with doxycycline. He suggested it prevents reconsolidation of memories.
“I believe if it works, it could be a treatment that is much simpler and much shorter than a psychotherapy, and I guess it could be very beneficial.”
Bach helped conduct a study involving 76 healthy participants, half of whom were given the antibiotic while the other half received a placebo.
They were then exposed to the colors red or blue on a computer screen, each volunteer receiving a mild electric shock when they saw one of the colors and not the other. Each volunteer came to associate pain with a particular color.
A week later, the participants were brought back into the lab. But instead of receiving a shock, they heard a loud noise when they saw the color that was previously associated with the shock.
The volunteers who were under placebo had a stronger reaction when they saw the color that predicted the electric shock. It wasn't much, a slight increase in the body's reflexive eye blink response to threat. But that increase, Back said, "was reduced in the people that initially took the doxycycline.”
The increased blink response in the placebo group signaled they were more startled and fearful of the noise than the doxycycline group. The fear response was 60 percent lower in those who received the antibiotic.
A startling noise often sets off an episode in people with PTSD.
The finding was published in the journal Molecular Psychiatry.
The goal, Bach says, is not to delete traumatic memories, but to use the calming effects of doxycycline to reimagine them in a way that stops scaring the patient.
If the tests continue to show positive results, Bach says doxycycline could be ready to treat PTSD in a few years.