Sharp mood swings. Problems sleeping. The overwhelming urge to gather with family. The irresistible need to lay in stores of food.

All these symptoms are affecting North Americans literally by the millions as they struggle to absorb the implications of last week's catastrophic attacks in New York and Washington.

And all of them are utterly normal, say experts in traumatic stress. They even have a name: radiated distress. It's a syndrome of physical, psychological and emotional responses to great calamity, triggered by an involuntary flood of adrenaline. It affects people not directly in the thick of the crisis but emotionally connected to it.

"We feel like our safety has been disrupted," said Anna Baranowsky, a psychologist who is a director of the Canadian Traumatic Stress Network. "It literally has an impact to our nervous system."

She said people need to have "an extreme amount of tolerance" for the ways in which their bodies are reacting to the horrific attacks.

"Remember, this is a normal reaction to an abnormally stressful event," she said. "It's the event that's abnormal; the response is automatic. That's the way the body protects us, even at a distance."

She divided the array of behaviour into three broad types, each based on the primal need to survive great danger. The first is an instinct to fight. In North Americans trying to come to terms with last week's tragedy, that can take the form of gathering things for the family. One woman reported a bout of baking whole-wheat muffins for her children.

In Calgary, school officials report that students are saying they care about their teachers and reaching out to parents to say "I love you" a little more often.

"Not in an anxious way," said Denise Still, director of the critical-incident response team at the Calgary Board of Education, ". . . just in a thoughtful way."

The second instinct is to flee. For North Americans, that is taking the form of a sense of unreality.

The third response is to freeze. If people can't figure out how to fight or run, they block everything out.

Bob Stein, head of child and adolescent psychiatry at North York General Hospital in Toronto, said his unit is trying to encourage children to talk to parents about their worries. He is calling on parents to project calm confidence.

As for adults, one of the best things they can do is to exercise and drink lots of water, Dr. Baranowsky said. This helps flush adrenaline from the body. As well, it is wise to limit caffeine and alcohol, and to eat foods low in fat and sugar.