I have autism, and people with autism tend to have the mental age of someone far younger. Because of brain damage in autism, i feel that i have the actual mental age of only 13! I actually WANT to be 13, because that is how mentally young i feel, but i don't want to tell anyone my real age. I would say that my mental age is 13, which is also my emotional and social age. I reckon that by the time i am 30, i will have the actual mental age of between 14 and 16.