Watch these recommended TED-Ed Lessons:

How stress affects your brain
Stress isn’t always a bad thing; it can be handy for a burst of extra energy and focus, like when you’re playing a competitive sport or have to speak in public. But when it’s continuous, it actually begins to change your brain. Madhumita Murgia shows how chronic stress can affect brain size, its structure, and how it functions, right down to the level of your genes.

The psychology of post-traumatic stress disorder
Many of us will experience some kind of trauma during our lifetime. Sometimes, we escape with no long-term effects. But for millions of people, those experiences linger, causing symptoms like flashbacks, nightmares, and negative thoughts that interfere with everyday life. Joelle Rabow Maletis details the science behind post-traumatic stress disorder, or PTSD.

The psychology behind irrational decisions
Often people make decisions that are not “rational” from a purely economical point of view — meaning that they don’t necessarily lead to the best result. Why is that? Are we just bad at dealing with numbers and odds? Or is there a psychological mechanism behind it? Sara Garofalo explains heuristics, problem-solving approaches based on previous experience and intuition rather than analysis.

What if our healthcare system kept us healthy?
Rebecca Onie asks audacious questions: What if waiting rooms were a place to improve daily health care? What if doctors could prescribe food, housing and heat in the winter? At TEDMED she describes Health Leads, an organization that does just that -- and does it by building a volunteer base as elite and dedicated as a college sports team.

The mysterious workings of the adolescent brain
Why do teenagers seem so much more impulsive, so much less self-aware than grown-ups? Cognitive neuroscientist Sarah-Jayne Blakemore compares the prefrontal cortex in adolescents to that of adults, to show us how typically “teenage” behavior is caused by the growing and developing brain.