Allergy medication may do more than clear up a stuffy nose, according to a new report that shows that diphenhydramine — the antihistamine in Benadryl — stymies the recall of aversive negative memories in humans.

Haunting memories are a prominent feature of posttraumatic stress disorder (PTSD), which affects 7.7 million people in the U.S., according to the National Institutes of Health. But not everyone who lives through a traumatic experience will suffer from recurring, painful memories.

Subtle traits in a person’s genome may be at fault, according to this report from geneticists at the University of Basel, Switzerland.

The researchers compared the genomes of 2,500 healthy young volunteers after they had completed an emotional memory performance test. The team uncovered a group of gene traits that were more common in people who had easier time recalling negative memories.

Next, the scientists cross-checked this list of traits with a catalog of approved drugs to see if any of the former could be manipulated clinically. They opted to remove compounds that could trigger severe side effects and moved forward with a smaller set of nine gene-drug pairings.

These nine traits were examined again in biological data from a second group of 340 holocaust survivors to whittle the subset down to one gene target heavily linked with traumatic memory recall.

The final winner was the gene for histamine receptor H1 (HRH1), whose overstimulation with allergies contributes to runny noses and asthma.

To test whether antihistamines could stymie negative memories, 40 individuals took diphenhydramine and were given an exam where they had to recall upsetting events. Diphenhydramine significantly reduced the recall of negative memories, but had no effect on positive or neutral memories.

“The rapid development of innovative methods for genetic analysis has made this new and promising approach possible,” said co-lead author and professor Andreas Papassotiropoulos of the Psychiatric University Clinics at the University of Basel. “In a further study, we will try to identify and develop memory enhancing drugs.”

 

Source: Papassotiropoulos A, Gerhards C, Heck A, et al. Human genome–guided identification of memory-modulating drugs. PNAS. 2013.