If you think you’re stressed, consider the walrus.

As their sea-ice habitat shrinks, the creatures are being pressed ever closer, raising adrenaline and anxiety to dangerous levels. Last month, The Times reported, tempers flared in a colony near Icy Cape, Alaska, and 131 walruses were crushed in a panicked stampede.

Walruses are not alone in their overreaction to stress. Whether in primordial ooze, a melting ecosystem or a collapsing job market, animals are hard-wired to either fight or flee, as brain chemicals and hormones spike according to real, or imagined, threats.

Unfortunately, humans have a talent for exaggerating the imagined ones.

As Natalie Angier wrote in The Times, “humans can think too much, extracting phantom threats from every staff meeting or high school dance. The risk, she wrote, is that the stress response, so effective in a sudden escape from a saber-toothed tiger, becomes harmful if it never lets up. Like lab rats crammed into crowded cages, anxious humans risk developing compulsive thought patterns and physical ailments.

Some of those compulsive patterns persist during sleep. With the downturn in the economy, American dentists are noticing a concurrent upturn in tooth grinding, a subconscious muscle activity related to stress. Most grinders are unaware of the problem, until a tooth fragments, The Times reported.

Once again, the fault lies as much in our primordial ancestors as our modern financial system.

“Stress, whether it’s real or perceived, causes fight-or-flight hormones to release in the body, Dr. Matthew Messina, a dentist in Cleveland, told The Times. “Those released stress hormones mobilize energy, cause isometric activity, which is muscle movement, because that built-up energy has to be released in some way.

Downturn or not, some of those tooth grinders may have been “wired to worry since birth, according to The Times Magazine. Jerome Kagan, a professor of psychology at Harvard University, has been studying the personality traits of a group of people since 1989, when they were all infants. One known as Baby 19 caught his attention from the start. She was fidgety and fearful and unraveled with changes of any kind, whether new sounds, sights or people. Like many other overly reactive infants Mr. Kagan studied, Baby 19 grew up to be a high-strung young woman with a social anxiety disorder and a constant sense of impending doom.

Brain scans of such people reveal hyperactivity in the amygdala, the center of the brain related to, as one might suspect, primitive fight or flight responses.

The good news is that we can undo persistently compulsive patterns.

Unlike the ill-fated, stressed-out walruses of Icy Cape, some of Dr. Kagan’s hyper-reactive subjects benefited from cognitive therapy that rechanneled their thought patterns away from the constant grind of fear and anxiety.

“Inner struggles pulled at me for years, one wrote at the wise old age of 13, “until I was able to just let go and calm myself.


For comments, write to nytweekly@nytimes.com.