The Goldilocks Principle of Stress: Too Little Is Almost As Bad as Too Much

TIME:

A life free of stress and adversity sounds blissful. But, in fact, the happiest and healthiest people are those who have had at least some early exposure to negative experiences, according to a new research review.

Despite the popular notion, stress isn’t all bad. In fact, low to moderate amounts of stress are necessary for healthy growth. What’s harmful is large doses of uncontrollable stress — experiencing a natural disaster, for instance, or living in extreme poverty — particularly in early life. Also harmful, it turns out, is having experienced no stress at all.

The new review adds weight to a growing body of evidence that most brain systems function like muscles: they are strengthened through exposure to gradually increasing loads at the appropriate stages of development, but they will wither without exercise and get injured if they are suddenly overloaded without prior training. The stress system is a prime example.