The ‘post’ in post-traumatic stress

DAVID DOBBS

In 1980, the Diagnostic and Statistical Manual of Mental Disorders defined trauma as "a recognisable stressor that would evoke significant symptoms of distress in almost everyone"—universally toxic, like a poison. But it turns out that most trauma victims rebound to live full, normal lives. That has given rise to a more nuanced view of trauma—less a poison than an infectious agent, a challenge that most people overcome but that may defeat those weakened by past traumas, genetics or other factors.

The idea was demonstrated vividly in two presentations this fall at the University of California, Los Angeles, US. Each described reframing a classic model of traumatic experience—one in lab rats, the other in child soldiers.

In the first case, Paul Plotsky, a neurobiologist at Emory University, described what happened when he tweaked one of the most widely used models of how maternal separation affects young rats. The model was created in the early 1990s by Plotsky himself to bring consistency to the way maternal separation is studied. Earlier experiments kept mother and pups apart anywhere from one to 24 hours; Plotsky reset those periods to 15 minutes and 180 minutes.

After a 15-minute separation, a mother would typically sniff and lick each pup, then gather and feed them, all the while conversing with them in gentle, ultrasonic warbles. After a 180-minute separation, however, most mothers would dash about emitting panicky squeaks, often stomping on the pups or ignoring them. And for the rest of their lives, they had outsize physiological and behavioural reactions to stress and challenge.

This "15/180" model quickly became a standard, generating scores of studies showing that long separations created anxious rodents with permanent changes in stress-hormone activity, brain structure and many other measures.

Then about five years ago, Plotsky was thinking about the mother's post-separation panic when, he said, "it hit me: maybe she views her environment as unsafe" because she and her pups are back in the same cage as the one they were taken from. So he upgraded the simple cage to a complex one. The separated rat family now reunited not in the kidnapping site but in the antechamber of an eight-room condo.

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