When mental health professionals attempt to make the diagnosis of OCD, they’re going to want to make sure that the obsessions or compulsions are not better accounted for by another disorder. For example, individuals with eating disorders have many rituals about how they will eat or touch food, but that may be more a result of the eating disorder than of OCD. (It’s true that a person could have both diagnoses as well, which is why a professional needs to conduct a thorough interview with the patient and the patient’s significant other, family, or friends.)
Also, the amount of time spent ritualizing is important. If the rituals do not take up much time in a person’s day (under an hour), a diagnosis of OCD may not be appropriate. Or if the obsessive thoughts are not significant enough to cause much distress, or if the person is unable to recognize that the compulsions are excessive (this does not apply to children), then an OCD diagnosis may not be warranted. At least one of the above criteria (time, significant distress, or recognition) has to be present for a diagnosis of OCD.
Basically, the effects of the obsessions and compulsions need to be significant enough to cause a lot of distress in a person’s life, to be not better accounted for by another mental health disorder, and to be recognized by the person as excessive, even though the person feels compelled to perform them anyway. If people do meet some, but not all, of the criteria for OCD, then the diagnosis of anxiety disorder not otherwise specified (NOS) would be appropriate. A person could still get treated for the OCD-like symptoms, even if he or she did not meet the full criteria for OCD.