Final answer:
OCD is predominantly characterized by repetitive thoughts and recurring, irresistible impulses, with its symptoms causing significant impairment in daily functioning and quality of life.
Step-by-step explanation:
Obsessive-compulsive disorder (OCD) is associated with repetitive thoughts and recurring, irresistible impulses, which are known as obsessions and compulsions, respectively. While physical signs without a physiological cause may suggest Conversion Disorder or Somatoform Disorders, and apprehension and inability to concentrate may be part of the anxiety spectrum, the defining features of OCD are the presence of persistent obsessions—repetitive, intrusive thoughts, images, or urges that the individual finds distressing—and compulsions—repetitive behaviors or mental acts that one feels driven to perform in response to an obsession or according to rules that must be applied rigidly.
These symptoms can significantly interfere with a person's daily functioning and quality of life, as described in the family study of obsessive-compulsive disorder by Nestadt et al. (2000) and further emphasized in research on the impact of OCD on quality of life by Norberg et al. (2008).