Hi I wanted to respond to you about the Risperadal and weight gain. My son is also 4. He had just turned 4 when he was put on Risperadal and when they say weight gain is a side effect, they're not lying! Unlike your little guy, my son was not underweight to begin with but was "normal" for his age. He wore a size 4 or 4T. He's been on Risperadal for about 7 months and has gained 20 pounds! I weighed him the other day and was shocked to see he weighs 68 pound. He is seeing a child psychiatrist for the first time next week and I'm hoping they'll put him on a medication that will help him lose some of the 20 he's gained. As for the effects of Risperadal: At first I thought my prayers had been answered. My little boy was enjoyable to be around. He was a different child. Now, it seems his medication isn't helping him at all and we're back to where we were before the medication. My son was diagnosed with ODD, however I believe that he's actually ADHD and was misdiagnosed. My son is just hungry all the time. His appetite is just unreal. Then his pediatritian tells me to give him "age appropriate meals and when it's gone do not give him more to eat." Easy for him to say when he's not the one dealing with the child screaming and tugging on the refrigerator door begging for more food because he's still hungry.
Good luck with your son.