Pathological laughing and crying is when someone laughs or cries at inappropriate times or without a reason. Have you ever laughed when someone fell down or cried for no reason? That's normal, but when someone does it all the time for no reason, then it can be a problem.
Sometimes, a person's brain gets hurt or sick, and that can cause them to start laughing or crying uncontrollably. It's not their fault, and they can't control it. It can happen to anyone, even the grown-ups.
It can be hard when someone has pathological laughing and crying because people around them might not understand why they are laughing or crying so much. But it's important to be kind and patient with them because it's not their fault. Doctors and therapists can help them manage their laughing and crying so they can feel better.