Just a little clarification. There are two types of stimulant medication that are commonly used to treat ADHD. (By the way, ADHD or Attention-Deficit/Hyperactivity Disorder is the currently "correct" name for the condition, which can be present with or without hyperactivity/impulsivity.)

The first is methylphenidate (Ritalin is the most common brand name). The other is amphetamine, which is usually prescribed as the d form, or dextroamphetamine. The long-acting medication Adderall is a combination of salts of d and l forms of amphetamine.

Both these medications, if taken in excess, or taken by people who don't have ADHD, can produce a sense of euphoria and also dependence. In the doses we use to treat ADHD, we are simply replenishing neurotransmitters (dopamine and norepinephrine, mostly) that are present in inadequate levels in an otherwise normal brain. They are not sedatives, children are not "drugged" (unless the dosage is too high, in which case they can be sleepy or "overfocused"), and there is no dependence--the dose can be skipped completely for a weekend or a week, with no adverse effect, except for return of the ADHD symptoms.

Methamphetamine, also known as meth or speed, is a drug of abuse, not a pharmacologic agent. Saying that methylphenidate is "very similar" to speed is technically true, but not very meaningful. Testosterone is "very similar" to estrogen, but, fortunately, they don't have quite the same effect.

Aloha,
Mark

PS, for those who don't know, I've been a pediatrician for 25 years, and I now have a position as a developmental pediatrician (I'm Board-certified in both Pediatrics and Developmental-Behavioral Pediatrics.) I'm also a perennially mediocre guitarist and singer, which is just as much fun as my day job.