The nature and type of Pure-O varies greatly from person to person, but the central theme for all sufferers is the emergence of a disturbing intrusive thought or question, an unwanted/"inappropriate" mental image or a frightening impulse that causes the person extreme anxiety because it is antithetical to closely-held religious beliefs, morals, or societal mores. While those without Pure-O might instinctively respond to bizarre intrusive thoughts or impulses as insignificant and part of a normal variance in the complex & creative human mind, someone with Pure-O will respond with profound alarm followed by an intense attempt to neutralize the thought or avoid having the thought again. The person begins to ask themselves constantly “Am I really capable of something like that?” or “Is that really me?” and puts tremendous effort into escaping or resolving the unwanted thought. They then end up in a vicious cycle of mentally searching for reassurance and trying to get a definitive answer.
Sexuality including recurrent doubt over one's sexual orientation (also called HOCD or "homosexual OCD" or "gay OCD").
People with this theme display a very different set of symptoms than those actually experiencing an actual crisis in sexuality. Most people with this type of obsession are in healthy and fulfilling romantic relationships, either with members of the opposite sex, or the same sex.
Violence which involves a constant fear of violently harming oneself or loved ones or persistent worry that one is a pedophile and might harm a child.
Religiosity manifesting as intrusive thoughts or impulses revolving around blasphemous and sacrilegious themes.
Responsibility with an excessive concern over someone's well-being marked specifically by guilt over believing they have harmed or might harm (either on purpose or inadvertently) someone.
Health including consistent fears of having or contracting a disease (different from hypochondriasis) through seemingly impossible means (for example, touching an object that has just been touched by someone with a disease) or mistrust of a diagnostic test (for example, repeatedly being tested for HIV).
For example, the question "Am I gay?" might lead a person to continually surf the web at work, reading numerous articles on defining one's sexual identity. This reassurance seeking ritual will, ironically, provide no further clarification and will likely exacerbate the intensity of the search for the answer.
The disorder is particularly easy to miss by many well-trained clinicians, as it closely resembles markers of Generalized anxiety disorder and does not include observable, compulsive behaviors. Clinical "success" is reached when the Pure-O sufferer becomes indifferent to the need to answer the question. While many clinicians will mistakenly offer reassurance and try to help their patient achieve a definitive answer (an unfortunate consequence of therapists treating Pure-O as Generalized Anxiety Disorder) this method only contributes to the intensity or length of the patient's rumination, as the neuropathways of the OCD brain will predictably come up with creative ways to "trick" the person out of reassurance, negating any temporary relief and perpetuating the cycle of obsessing.
According to Dr. Steven Phillipson, a pioneer in the study and treatment of Pure-O, the most effective treatment for Purely Obsessional OCD is Cognitive-Behavioral Therapy. More, specifically, Exposure and response prevention (ERP) which may or may not be combined with the use of medication, such as an SSRI.