Most important point is the change in the pattern of children life before and now. Also to be noticed the change in the family behaviour. Parents stress
results as frustration in children's behaviour and ultimately aggression.We have to be very clear in our mind that children are replica of us as parents. Since he is 4 years now so may be he has just started going to school. And few new behavioural changes adopted from the surrounding friends. Pl. check on the school friends and consulting teacher make some changes in sitting arrangement. May be now a days he is being given less attention than before for some reason and he is trying to divert the attention of parents to him.
In my view, no modicine, no doctor's consulation would give better result than giving total attention and love will improve.