One of the most common and well supported styles of psychotherapy for Generalized Anxiety Disorder (GAD) is Cognitive-Behavioral Therapy (CBT). The following article will give an overview of this approach and why it works so well for GAD.
The hallmark of CBT is an intense focus on thought processes and belief systems. The overall goals of the approach are to help people identify problematic beliefs and thought patterns, which are often irrational or unrealistic, and replace them with a more rational and realistic views. This is generally accomplished in a supportive environment that can often feel like a classroom, with the treatment professional assigning homework, highlighting concepts, and helping the client through a path of self-discovery and change. CBT is most often associated with Aaron Beck and Albert Ellis, who have slightly different views on treatment.
Typically, one of the first tasks of the client is to learn to identify certain types of problematic thoughts called "cognitive distortions" (click here for a list, desccription, and examples of common cognitive distortions). These are systematic ways that people can twist and distort information coming in from the environment that can significantly increase anxiety and reduce coping resources. Theoretically, if a person is able to identify when he/she is using these, and is able to replace them with a more realistic view, then anxiety is reduced.
A schema is another important concept in CBT. Essentially, a schema is a network of information that dictates how people think about things and interpret the world. There are schemas for everything: computer, freedom, anxiety, and self. Longer term work in CBT is focused on changing schemas, which are at the core of one's belief system. An important part of this process is identifying "automatic thoughts", which are thoughts that occur instantly when thinking about something. For example, if someone had significant anxiety around public speaking, simply thinking about it can trigger "embarrassment", "fear", and "failure" or a previous experience. Working to change automatic thoughts and creating more accurate and positive networks of information can take a significant amount of time, but often result in long term reductions in anxiety.
Finally, one of the main reasons CBT has become so popular is because of how much research has demonstrated its effectiveness. There are a large number of well constructed experiments that have show it to be highly useful in treating depression and anxiety disorders, including GAD. The key factors for it to be helpful are buying in to the belief that it will help, completing relevant assignments, and a willingness to confront uncomfortable thoughts. Although many CBT techniques can difficult to do at first, for most people the remission of GAD is well worth the struggle.
Source: Beck, J.S. (1995). Cognitive Therapy: Basics and Beyond. Guilford Press.