Usually, mild OCD symptoms start showing up in childhood, but the full disorder often doesn't develop until the teenage years or early twenties. Most people who develop OCD will have it for a long time, with symptoms getting better and worse over the years. One study found that mild symptoms typically started around age 16 and full OCD around age 19, though any kind of symptom usually first appeared around age 10. In that same study, about 37% of OCD cases and 29% of mild symptom cases had started by ages 19-20. Very few new cases developed after age 30, which shows that OCD usually begins by early adulthood and rarely starts later in life.