What is the primary characteristic of obsessive-compulsive disorder?

The primary characteristic of obsessive-compulsive disorder (OCD) is emotional and behavioral symptoms manifesting as obsessions and compulsions. Obsessions are intrusive and unwanted thoughts, images, or urges that create significant anxiety or distress. Compulsions, on the other hand, are repetitive behaviors or mental acts that a person feels driven to perform in response to the obsessions, often aimed at reducing the anxiety those obsessions cause, or preventing a feared event. This cycle of obsessions and compulsions greatly impacts an individual's daily life, affecting their ability to function normally.

The other options do not accurately describe OCD. Sudden intense fear is more characteristic of panic disorders, while existential worries are more associated with anxiety or depression but not specifically OCD. Seasonal mood shifts relate to seasonal affective disorder, which has a different focus on mood changes corresponding to seasons. Thus, emotional and behavioral symptoms become central in defining OCD, making it the most accurate answer.