This is Hidden Brain, I'm Shankar Vedanta.

When you're eight years old, it's not easy to say goodbye to your dad for a whole year.

But that's what Andrew Marvin had to do.

His dad was a commander in the Navy and was deployed to Bahrain.

While his dad was away, something happened to Andrew.

Every time my husband's name was brought up, he would develop a headache.

This is Andrew's mom, Anne-Marie Marvin.

She knew her son's pain was real.

She didn't want him to suffer.

As she tried to figure out how to help, she remembered an episode of the TV show, Mash.

The series is set in a fictionalized army hospital.

Come on guys, let's go back to the tent.

The doctors had a problem on their hands.

The hospital was full of wounded soldiers, but was out of painkillers.

A Colonel suggested an unusual solution.

Treat the patients with a placebo.

Here's the formula.

If we believe it, they believe it.

Otherwise, they're only taking sugar pills.

The doctors gave out the placebos, while pretending they were real pills.

Sure enough, it worked.

You're really beginning to kill it, aren't you, son?

...