Could a Common Antibiotic Help Treat Post-Traumatic Stress Disorder?

A commonly used antibiotic may help prevent or treat posttraumatic stress disorder (PTSD), according to a study published inMolecular Psychiatry.

The study was a preregistered, placebo-controlled, double-blind, randomized, controlled trial that included 76 healthy volunteers.

In the first session, the participants were given either doxycycline or placebo and were put in front of a computer screen that would flash either blue or red. One of the colors was associated with a 50% chance of receiving a painful electric shock.

This occurred 160 times, with the colors appearing in random order so the participants learned to associate the “bad” color with the shock.

One week later the participants repeated the experiment under no medication. This time there were no electric shocks but rather a loud sound that played after either color was shown. The investigators measured their fear responses by tracking their eye blinks.

The fear memory response was then calculated by subtracting the baseline startle response—–the response to the sound of the “good” color––from the response to the sound when the “bad” color was shown.

The results of the study showed that the fear response was 60% lower in participants who had doxycycline in the first session compared with the placebo. The findings suggest that the fear memory was significantly suppressed by doxycycline.

Other cognitive measures, including sensory memory and attention, were not affected, according to the study.

“When we talk about reducing fear memory, we are not talking about deleting the memory of what actually happened,” said lead author Dominik Bach. “The participants may not forget that they received a shock when the screen was red, but they ‘forget’ to be instinctively scared when they next see a red screen. Learning to fear threats is an important ability for any organism, helping us to avoid dangers such as predators. Over-prediction of threat, however, can cause tremendous suffering and distress in anxiety disorders such as PTSD.”

An estimated 70% of adults in the United States have experienced some type of traumatic event at least once in their lives, of whom, 20% go on to develop PTSD, according to PTSD United. This equates to approximately 44.7 million people who were or are struggling with PTSD. Furthermore, an estimated 8% of Americans have PTSD at any given time.

“We have demonstrated a proof-of-principle for an entirely new treatment strategy for PTSD,” Bach said. “The theory is based on the recent discovery that our brains need proteins outside of nerve cells, called matrix enzymes, to form memories. Matrix enzymes are found throughout the body, and their over-activity is involved in certain immune diseases and cancers. To treat such diseases, we already have clinically approved drugs that block these enzymes, including the antibiotic doxycycline, so we wanted to see if they could help to prevent fear memories from forming in the brain. Our results support this theory, opening up an exciting avenue of research that might help us to find treatments for PTSD.

“Using drugs to prevent PTSD would be challenging, since in the real world we don’t know when a traumatic event is about to occur. However, there is growing evidence that people’s memories and associations can be changed after the event when they experience or imagine similar situations. This is called ‘reconsolidation,’ and we now plan to test the effect of doxycycline on reconsolidation of fear memories. If this is successful, we would hope to apply the technique to more clinically realistic models of PTSD within a few years.”