Although symptoms of OCD can begin at almost any age, research suggests that there are two distinct periods when OCD symptoms are most likely to appear. The first occurs around the ages of 10 to 12 or just before puberty and the second is between the ages of 18 to 23. People who develop OCD before puberty are considered to have early onset OCD while those who develop OCD later in life are considered to have late-onset OCD. Interestingly, there may be distinct differences in the symptoms, response to treatment, overlapping illnesses, brain structure and thinking patterns of people with early versus late onset OCD.
Differences in Gender, Symptoms and Treatment
One of the biggest differences between early and late onset OCD seems to be ratio of males to females. Studies have consistently found that males are much more likely to develop early-onset OCD than females. This gender difference seems to balance out among people who develop OCD later in life, with males and females being equally as likely to develop the disorder.
It has been also been noted that the earlier that symptoms appear, the more severe the symptoms are, and the more difficult they can be to treat with both psychological and medical treatments. Indeed, people with early-onset OCD may need to try more medications before finding relief from their symptoms and may need more trials of psychotherapy than people whose OCD begins later in life.
People with early-onset OCD often have a gradual appearance of symptoms, whereas people who develop OCD later in life tend to have symptoms that come on quickly and which are usually tied to some sort of trigger like a stressful life event (e.g., death of a loved one; loss of a job; failing out of school). An exception to this is rule is PANDAS; an autoimmune form of OCD that affects only children and in which symptoms appear very quickly.
Differences in Overlapping Illnesses
OCD often occurs with other illnesses (which are also called comorbid illnesses), however, the types of illnesses that occur with OCD seem to be influenced by when the person's OCD symptoms started. For example, while people with early onset OCD tend to have high rates of tic disorders and Tourette’s syndrome, late onset OCD is more commonly associated with depression and other anxiety disorders such as generalized anxiety disorder or panic disorder.
Differences in Brain Structure and Cognitive Function
The brains of people with people with early versus late onset OCD may be different from one another. Brain imaging studies suggest that people with early onset OCD have a reduction in the size of certain brain regions that are not evident in people whose OCD started later in life.
Interestingly, however, studies have consistently demonstrated that people with late-onset OCD score poorer on measures of cognitive (thinking) function than do people with early-onset OCD. It is not yet clear why this is case and whether this has any impact on treatment.
Sources:
Lomax, C.L., Oldfield, V.B., "Salkovskis, P.M. Clinical and treatment comparisons between adults with early- and late-onset obsessive-compulsive disorder." Behavior Research and Therapy 2009: 99-104
