Humor is serious business. Sure, there's simple comedy like a pie in the face or an Adam Sandler movie, but a lot of jokes display real intellect, and despite much reflection and experimentation—both in labs and on stages—no one has yet discovered a unified theory of hilarity.
Stress is simply a reaction to a stimulus that disturbs our physical or mental equilibrium. In other words, it's an omnipresent part of life. A stressful event can trigger the “fight-or-flight” response, causing hormones such as adrenaline and cortisol to surge through the body.
Anxiety is a normal reaction to stressful situations. But in some cases, it becomes excessive and can cause sufferers to dread everyday situations.
This type of steady, all-over anxiety is called Generalized Anxiety Disorder.