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Some babies cry, scream and kick in response to unfamiliar situations while others remain calm. The difference between the two stays with them throughout their lives, predicting their susceptibility to depression and anxiety disorders, finds a new study presented at the annual meeting of the American College of Neuropsychopharmacology, Dec. 7–11, in Scottsdale, Ariz.

The study's lead researcher, Carl Schwartz, MD, a psychopathologist at Massachusetts General Hospital in Charlestown, found that a baby's temperament—reliably discernable at 4 months of age—predicts the structural development of the anterior prefrontal cortex, the brain area heavily involved in emotional response and control.

"Every parent is intrigued by the differences in children that are present from the day they're born," Schwartz says. "We've discovered a surprising, and we think important, link to depression and anxiety."

Schwartz and colleagues tracked 76 people from infancy to adulthood, recording their behavior and imaging their brains once at 4 months and again at 18 years using MRI. They found that babies who were highly reactive to new experiences were 10 times more likely to develop depression and anxiety disorders in adulthood than were less reactive children. Also, adults who had been highly reactive babies grew thick prefrontal cortexes, Schwartz says. The prefrontal cortex is richly connected to the amygdala, which coordinates emotional memories, and the hippocampus, which controls the fear response. Schwartz thinks increased cortical thickness might interfere with the proper functioning of these brain regions, leading to increased depression and anxiety.

Schwartz cautions, though, against generalizing his findings to all cases of prefrontal cortical thickness. "Anatomy isn't destiny," he says. "But anatomy does seem to have a pretty big footprint."

—M. Price