Researchers are finding there is nothing to fear but biology itself: Two new studies hint that genes may control not only how scared we get but also how long we stay afraid. Psychiatrist and neurologist Daniel Weinberger of the National Institute of Mental Health explored a long-suspected link between fear and a gene involved in regulating the brain's response to serotonin, a potent neurotransmitter. He and his team showed photographs of fearful faces to volunteers and then measured their reactions using MRI brain scans. People with a particular variant in the serotonin-control gene showed more activity in the amygdala, the emotional control center of the brain, and felt more anxious after seeing the photos. "Population-wide studies have already demonstrated that people with that variant are more likely to report fearfulness. Showing how that translates into brain activity makes the argument for a genetic influence pretty convincing," Weinberger says.
Genes may also mediate how we find our way out of our duress, says Beat Lutz of Germany's Max Planck Institute of Psychiatry. His team engineered mice whose brains cannot respond to naturally calming compounds called endocannabinoids. Lutz gave both engineered and normal mice an electric shock, administered simultaneously with a loud tone, and then started playing only the tone. Normal mice soon became blasé when they heard the tone, but those lacking endocannabinoids worked themselves into a frenzy long after the shocks were over. "This could explain why some soldiers recover quickly, while others end up dealing with shell shock for decades," Lutz says. The finding may indicate that treatments aimed at boosting endocannabinoids could soothe the aftermath of bad experiences.