You have a 2 yr old. Is there higher stress, or less structure than normal in the house?
My thoughts (I have an almost 7 & almost 3). My son is also VERY intelligent & "spazzes" from time to time. He tries, especially now that his sister is hitting the cute phase, to act like he's 2. He sees her getting attention & tries it out himself. Problem is, its not that long ago that that phase was his.
When the daily routine is interruppted for a longer period of time (Summer for one), then he seems to "digress" more. With his intelligence, comes a strong need for routine & when he lacks the routine, he becomes spazzy, babyish and sometimes downright annoying (because he no longer acts his age).
Try establishing a daily routine (that includes 1 on 1 age appropriate time ex. Reading before Bed). Stick to your Routine a few weeks & see if he starts getting back to his age. Before bed 1 on 1 seems to work best, because as life gets hectic, it gives a daily time to feed their need for attention & calm down before bed. Make sure to Praise him for things he's good at and remind him, if needed of his age.
Hope this helps...
Unless he's disruptive with his behavior, give life a chance to calm down, before seeking too much treatment. Unless you want a kid on drugs, or in therapy for being a kid.