It could be that your son may have had enough symptoms to meet the diagnostic criteria at the time but is growing out of it naturally on his own and/or what you are doing for him is working.
Here is a convoluted explanation of what I mean:
http://www.ncbi.nlm.nih.gov/pubmed/16209748He's definitely changing. His original diagnosis was combined type, but now his only symptoms are inattention. I think he falls under either the "get better with treatment" or "get better on his own/is outgrowing it" category...
