Which of the following is a defining characteristic of obsessive-compulsive disorder (OCD)?

Unwanted intrusive thoughts are a defining characteristic of obsessive-compulsive disorder (OCD). Individuals with OCD frequently experience distressing thoughts, images, or impulses that they cannot control; these are the intrusive thoughts. These thoughts often provoke significant anxiety and discomfort, leading individuals to engage in compulsive behaviors in an attempt to alleviate the distress caused by the obsessions.

Intrusive thoughts are typically unwanted and can revolve around themes of harm, cleanliness, symmetry, or various fears, which can significantly impair daily functioning and overall quality of life. The presence of these thoughts is critical for the diagnosis of OCD and distinguishes it from other anxiety disorders.

The other options, while they may be associated with various mental health issues, do not specifically define OCD. High levels of energy may pertain to different conditions, social withdrawal can be seen in various anxiety and mood disorders, and chronic fatigue is more commonly associated with depression or medical conditions rather than being a hallmark of OCD.