Ask Dr Gary: Different effects of Ritalin

I have a question about Ritalin. Kids with ADHD (attention deficit hyperactivity disorder) take it to calm down, yet it's a drug that's related to methamphetamine, which makes people hyperactive and insane. How can one type of drug have such different effects? - Lily

Ritalin is methylphenidate, a man-made stimulant that puts it in the same broad family as cocaine, methamphetamine, ecstasy, caffeine, and nicotine. The stimulants, universally used and abused, all share a reputation as "uppers", drugs that increase alertness, endurance, motivation and arousal. They have their downsides, too.

At too-high doses stimulants, especially the illegal kind, cause increased anxiety, fear, fast heart beats, high blood pressure and sometimes provoke seizures, strokes and heart attacks.

What makes people with ADHD a bit different is that parts of their brain are dopamine-deficient compared to people without ADHD. PET scans have shown this convincingly.

Dopamine is the main neurotransmitter in our brain responsible for learning, motivation and reward-seeking behaviour. When we're deficient we can lose motivation, withdraw socially, become hyperactive or lose our ability to focus.

Schizophrenia, social anxiety, and ADHD all share a common theme of dopamine-deficiency, albeit in different parts of the brain. Mania is at the opposite end of the spectrum and is associated with dopamine levels running amok. Average, regular folks are somewhere in the middle of the spectrum.

Ritalin increases dopamine levels in ADHD patients to levels nearer those of regular folks, letting them focus and study for longer periods of time, and more successfully resist distractions.

But if you're not dopamine-deficient, taking additional stimulants is less likely to make you happily productive, and more likely to just make you freak out. Same medicine, different brain, different outcome.