8. Generalized anxiety disorder

Generalized anxiety disorder (GAD) is a relatively new concept. Worry is the main characteristic of GAD, which can be a highly debilitating illness, with profound effects on a person's career, relationships, and overall wellbeing. About 3% of people suffer from generalized anxiety disorder, and women are twice as likely to be affected as men. There are four main theories of worry: the metacognitive model; the cognitive avoidance theory; intolerance of uncertainty; and the mood-as-input theory.