Shankar Vedantam

This is Hidden Brain.

I'm Shankar Vedanta.

For centuries, physicians regarded fever as a dangerous disease, an enemy to be crushed.

In ancient and medieval medicine, fever was thought to represent an excess of heat or humor in the blood, a sign that the body's internal balance had gone dangerously askew.

Treatments aimed to drive out the heat.

Patients were bled, purged, or doused with cold water.

Some were packed in ice, or fed diets designed to cool the blood.

Well into the 19th century, fever was still widely feared as a destructive force that could consume a person from within.

Doctors prescribed mercury-based compounds, quinine, or alcohol in large quantities.

Patients were subjected to fever cures in which they were submerged in prolonged cold baths or were wrapped in vinegar-soaked sheets, all in the hope of forcing the body's temperature back down.

It wasn't until the late 19th and early 20th centuries that scientists began to recognize fever not as a disease, but as a natural response of the body's immune system.

Research showed that infections, not fever, were the real enemy.

Studies showed that moderate fever actually helped the body fight infection by slowing the growth of bacteria and enhancing immune function.

This shift marked a profound change in medical thinking.

Instead of reflexively suppressing fever, physicians began to see it as evidence of the body's vitality and capacity for self-defense.

Today, while very high fevers are still considered dangerous and treated, mild to moderate fevers are often allowed to run their course, a quiet acknowledgement that what was once seen as a deadly illness

is, in fact, a sign of the body's strength.

Today on the show, we investigate the possibility that what is true of our physical health may also be true of our mental health.

That even a scourge like depression may have its roots in our powerful drive to survive and flourish.

The origins of depression, this week on Hidden Brains.