Define obsessive-compulsive disorder (OCD).

Obsessive-compulsive disorder (OCD) is accurately defined by its hallmark features: unwanted, persistent thoughts, known as obsessions, and repetitive behaviors or mental acts, known as compulsions, that individuals feel driven to perform in response to those thoughts. For instance, a person with OCD might experience intrusive worries about contamination (obsessions) and feel compelled to wash their hands excessively (compulsions) to alleviate their anxiety. This definition encompasses the core aspects of OCD, describing both the nature of the intrusive thoughts and the resultant behaviors that individuals engage in to cope with those thoughts.

The other choices do not adequately capture the essence of OCD. While occasional anxiety is a general symptom that might appear in various conditions, it is not specific or unique to OCD. A chronic mood disorder, which emphasizes sustained feelings of sadness or irritability, does not align with the characteristic thought-behavior cycle found in OCD. Similarly, a personality disorder primarily relates to pervasive patterns of behavior and thinking that affect interpersonal relationships, which does not reflect the specific nature of intrusive thoughts and compulsive actions central to OCD.