Washington ? Science is getting a grip on people’s fears.

As Americans revel in all things scary on Halloween, scientists say they now know better what’s going on inside our brains when a spook jumps out and scares us. Knowing how fear rules the brain should lead to treatments for a major medical problem: When irrational fears go haywire.

“We’re making a lot of progress,” said University of Michigan psychology professor Stephen Maren. “We’re taking all of what we learned from the basic studies of animals and bringing that into the clinical practices that help people. Things are starting to come together in a very important way.”

About 40 million Americans suffer from anxiety disorders, according to the National Institute of Mental Health. A Harvard Medical School study estimated the annual cost to the U.S. economy in 1999 at roughly $42 billion.

Fear is a basic primal emotion that is key to evolutionary survival. It’s one we share with animals. Genetics plays a big role in the development of overwhelming – and needless – fear, psychologists say. But so do traumatic events.

“Fear is a funny thing,” said Ted Abel, a fear researcher at the University of Pennsylvania. “One needs enough of it, but not too much of it.”

With counseling, self-study, calming exercises and introspection, panic-attack sufferers can learn how to stop or at least minimize those attacks early on. Scientists figure they can improve that fear-dampening process by learning how fear runs through the brain and body.

The fear hot spot is the amygdala, an almond-shaped part of the deep brain.

Emory University psychiatry and psychology professor Michael Davis found that a certain chemical reaction in the amygdala is crucial in the way mice and people learn to overcome fear. When that reaction is deactivated in mice, they never learn to counter their fears.

Scientists found D-cycloserine, a drug already used to fight hard-to-treat tuberculosis, strengthens that good chemical reaction in mice. Working in combination with therapy, it seems to do the same in people. It was first shown effective with people who have a fear of heights. It also worked in tests with other types of fear, and it’s now being studied in survivors of the World Trade Center attacks and the Iraq war.

The work is promising, but Michigan’s Maren cautions that therapy will still be needed: “You’re not going to be able to take a pill and make these things go away.”