Stimulants improve attentiveness; reduce hyperactivity, restlessness, and distractibility; and improve the ability to follow directions and stay on task.
By controlling aggressiveness and impulsiveness, these medications also have a dramatic impact on social relationships, both within the family and among peers. One study found that ADHD boys who started taking Ritalin were more likely to be rated as "cooperative" and "fun to be with" than they had been previously. Ritalin also reduces the incidence of verbal and physical aggression. And researchers find that when children are treated, parents and siblings respond with more warmth, more contact, less criticism, and greater cooperativeness.
The results are similar in the classroom: About 75 percent of ADHD children who are treated with stimulants show marked improvement according to teachers' evaluations. And these findings are borne out by measurements of the children's physical level of activity. Some research studies have used electronic monitors to measure ADHD children's level of activity, and they find that activity drops significantly with medication, both during daytime hours and during sleep. In fact, these changes can be detected as early as thirty minutes after the very first dose.
What are the benefits of stimulants for ADHD?
Of all the drugs used to treat ADHD, stimulants are the most consistently effective. What's more, they work quickly--often you can see changes starting with the very first dose.
In addition, stimulants are short-acting. They don't build up in the system. That makes it easier to fine-tune doses to get the best control. And it's reassuring to know that they clear the body quickly.
Also, stimulants have a decades-long track record of safe use in the treatment of ADHD. In fact, we know from this experience that they're among the safest medications prescribed to children.
What are the drawbacks?
While most people do well on stimulants, a small minority of patients can't tolerate the side effects (see discussion of side effects below), even after dosages are adjusted.
Another drawback is that control tends to be uneven with short-acting stimulants, because they do clear the system so quickly. As we'll see, you can time dosages to prevent this roller-coaster effect, but it can be a lot of work to maintain this schedule.
How do stimulants work?
Each nerve cell has two ends--a head and a tail, if you will. At the head, the cell manufactures chemicals known as neurotransmitters. As their name implies, these chemicals transmit an impulse from one nerve to the next.
The nerve cell stores these neurotransmitters until a signal reaches it; then it releases them from the head of the cell. Some of the neurotransmitters attach themselves to receptors on the next nerve's tail. They fit into these receptors like a key into a lock, triggering a signal in the second nerve. This signal, in turn, travels to the head of the second cell, where the process happens again. This chain reaction of chemical and electrical signals transmits the impulse along the nerve pathway.
To fire the second nerve, the first nerve has to release enough neurotransmitters to bind with the receptor sites. Normally, it releases more than necessary. After the neurotransmitters have done their job, the original cell recaptures some of them, storing them to be used again. But some of the neurotransmitters are destroyed. Thus, if you fire the nerves repeatedly, the cells deplete their supply of neurotransmitters and the nerves can't transmit signals as effectively until they manufacture more.
We're not quite sure what happens in ADHD, but it appears to involve a deficit in the neurotransmitters. The most powerful evidence for this idea is the fact that stimulants--and Dexedrine in particular--are close chemical cousins of the neurotransmitters and fit into the receptor "locks" quite nicely. It may be that they make up for a chronic deficit in natural neurotransmitters. Or the problem might be on the receiving end, with receptors that aren't sensitive enough. Or the medications might prompt nerve cells to produce or release more neurotransmitters. We simply don't know, because we don't yet have tools that can look at these processes on a chemical level in the brain.
What this complex process really boils down to is this: ADHD throws this electrical-chemical messenger system out of whack, creating "static" in the transmission. It's sort of like getting a weak signal from your television antenna-the picture gets through, but it's fuzzy. The medication acts to make the signal stronger so that the static disappears.
Chances are, the reason we see so many mimickers--and so many conditions that occur along with ADHD--is that so many factors can disrupt this delicate neurotransmitter balance and put static on the system. Depression, for example, upsets the balance of neurotransmitters, as do anxiety and other mood disorders. On the other hand, learning disorders such as dyslexia are not caused by alterations in this communication system, and therefore do not respond to medication.