Although many efforts have been made to subtype OCD in an effort to understand the relationship between these heterogeneous symptoms, considering the age of onset at which the disorder develops appears to be one of the most useful ways to understand how some patients with OCD may be distinct from others.9 Those who develop OCD as young adults appear to significantly differ from those who develop OCD at younger ages (mean age of 11).
People with late-onset OCD (mean age of 23 years) are slightly more likely to be female. This subtype of OCD is associated with a milder form of the illness and is less familial in comparison to those who develop OCD at younger ages. Late-onset OCD also has a greater comorbidity with anxiety and mood disorders, a lower rate of comorbidity with tics and spectrum conditions, and is associated with a better treatment outcome when compared to early onset OCD.
By contrast, men outnumber women at younger ages of onset and tend to have a greater severity of illness, poorer functioning, a higher prevalence of most types of obsessive-compulsive symptoms and a poorer response to treatment. Developing OCD at younger ages is also linked to a greater prevalence among first-degree relatives and a greater comorbidity with tics (10-40%) and spectrum conditions (but not anxiety, depression or attention-deficit disorder). Studies suggest that these individuals may have a higher frequency of alleles of the serotonin transporter promoter gene, greater neuropsychological impairment, and possibly have higher brain iron.9
Ten percent of those who develop OCD between the ages of three to puberty may also have pediatric autoimmune neuropsychiatric disorder associated with streptococcal infection (PANDAS). PANDAS is associated with a strep infection and a sudden onset of symptoms although some studies have not found a relationship between strep infections and later onset of OCD.