Good or fair insight is characterized by the acknowledgment that obsessive–compulsive beliefs are not or may not be true, while poor insight, in the middle of the continuum, is characterized by the belief that obsessive–compulsive beliefs are probably true. The absence of insight altogether, in which the individual is completely convinced that their beliefs are true, is also identified as a delusional thought pattern, and occurs in about 4% of people with OCD. When cases of OCD with no insight become severe, affected individuals have an unshakable belief in the reality of their delusions, which can make their cases difficult to differentiate from psychotic disorders.Some people with OCD exhibit what is known as overvalued ideas, ideas that are abnormal compared to affected individuals respective cultures, and more treatment-resistant than most negative thoughts and obsessions. After some discussion, it is possible to convince the individual that their fears are unfounded. It may be more difficult to practice exposure and response prevention therapy (ERP) on such people, as they may be unwilling to cooperate, at least initially. Similar to how insight is identified on a continuum, obsessive-compulsive beliefs are characterized on a spectrum, ranging from obsessive doubt to delusional conviction. In the United States, overvalued ideation (OVI) is considered most akin to poor insight—especially when considering belief strength as one of an ideas key identifiers—but European qualifications have historically been broader.
Furthermore, severe and frequent overvalued ideas are considered similar to idealized values, which are so rigidly held by, and so important to affected individuals, that they end up becoming a defining identity. In adolescent OCD patients, OVI is considered a severe symptom.Historically, OVI has been thought to be linked to poorer treatment outcome in patients with OCD, but it is currently considered a poor indicator of prognosis. The Overvalued Ideas Scale (OVIS) has been developed as a reliable quantitative method of measuring levels of OVI in patients with OCD, and research has suggested that overvalued ideas are more stable for those with more extreme OVIS scores. Cognitive performance
Though OCD was once believed to be associated with above-average intelligence, this does not appear to necessarily be the case. A 2013 review reported that people with OCD may sometimes have mild but wide-ranging cognitive deficits, most significantly those affecting spatial memory and to a lesser extent with verbal memory, fluency, executive function, and processing speed, while auditory attention was not significantly affected. People with OCD show impairment in formulating an organizational strategy for coding information, set-shifting, and motor and cognitive inhibition.Specific subtypes of symptom dimensions in OCD have been associated with specific cognitive deficits. For example, the results of one meta-analysis comparing washing and checking symptoms reported that washers outperformed checkers on eight out of ten cognitive tests. The symptom dimension of contamination and cleaning may be associated with higher scores on tests of inhibition and verbal memory. Children
Approximately 1–2% of children are affected by OCD.