Which of the following is NOT included in the types of anxiety disorders?

Obsessive-Compulsive Disorder (OCD) is classified separately from anxiety disorders in the DSM-5. Instead, it is included in a category called Obsessive-Compulsive and Related Disorders. While it shares key features with anxiety disorders, such as intrusive thoughts and heightened distress, the distinct nature of obsessions and compulsions sets OCD apart in its own diagnostic category.

In contrast, the other options—Selective Mutism, Panic Disorder, and Agoraphobia—are indeed categorized under anxiety disorders. Selective Mutism involves consistent failure to speak in social situations where there is an expectation to converse, reflecting a type of anxiety related to social interaction. Panic Disorder is characterized by recurrent, unexpected panic attacks and persistent worry about future attacks, embodying the core elements of anxiety. Agoraphobia involves intense fear or anxiety about being in places where escape might be difficult or help unavailable, and is fundamentally rooted in anxiety responses.

Thus, the distinction of OCD from anxiety disorders is why it is not included in the types of anxiety disorders according to the DSM-5.