Of all of the drug related causes of obesity out there perhaps none is more powerful than the gain associated with anti-psychotics. In adults gains of literally dozens of pounds are regularly seen.
A recent story by Postmedia's Sharon Kirkey on a new study out of BC to be published in the Canadian Journal of Psychiatry reports that in Canada, despite a total lack of evidence suggesting their safety in children (and moreover an almost total lack of studies involving children at all), since just 1996 second generation child anti-psychotic use has quadrupled.
While there's no singular cause for obesity, for children prescribed these meds obesity may come close to an inevitability. If your young child is currently on anti-psychotic meds, especially if they're on them for sleep, please consider making an appointment with your prescriber to discuss if there aren't in fact alternatives available.