I can tell you this my son was diagnosed at 5 at the end of Kindergarten after a very stressful year of telephone calls from the school and many letters home and once he started taking meds regularly he never got in trouble anymore and is able to actually focus on school. He is now 7 and in 2nd grade and has had straight A's all year and no notes home about behavior! He also takes focalin.
Tell your dh that ritalin has been around for over 60 yrs. The deaths caused were due to undxed heart conditions. Medication under the supervision of a doctor and well monitored should be no problem. I have a 14 yr old who was dxed at age 4. He is now a freshman in highschool and maintaining an A- average. He takes concerta, focalin for rebound ,as needed, melantonin and guanfacine. And, btw, he has tachicardia and a murmur. Heart problems run in our family.
I am a 60 yr old gm who is adhd and take a tricyclic med that helps my adhd symptoms. My dh is add, 2 of my adult children are adhd and 3 of my 8 gc are adhd and take various adhd meds. [one doesn't have an official dx yet]
My child, age five, was diangosed right after his fourth birthday. Even though, we knew at home that there was a problem. He is meds, and it has definitely improved his impulsivity. He is doing well in school and will be graduating kindergarten next month. This is great for a child that couldn't tell an A from a P at the beginning of the school year. He wouldn't let us help him. So, we are very proud of him.
Good luck.