This is actually true of virtually any drug that can be smoked or otherwise ingested. If you need to eat the drug (pot brownies, opium plants, mushrooms), there's a time lapse between ingesting the drug and when it gets into your bloodstream, and then when it gets up to your brain for the effects to begin. Smoking the drug puts it rather immediately into your bloodstream, and some blood fresh from the lungs goes straight to the brain, rather than wandering from the stomach to the lungs and then up. Snorting meth is usually quite fast in terms of reaction, simply because the blood around the nose is near the brain, and the drugs are likely to cross the blood-brain barrier. Snorting crystals of anything, however, damages the sinuses. Not irreparably, but a lot more than putting smoke into your lungs damages them. So, snorting is self-limiting in that way. I'd wager that shooting up meth would rival smoking it in terms of addiction, it's just not commonly done.

The previous answer is correct. Smoking a drug has the benefits of being fast acting, painless, easy to conceal, and (to a lesser degree) cost efficient. Snorting it can be quite painful and comes with a very unpleasant tasting drain in the back of your throat. Also, in relation to the amount you ingest, snorting it doesn't ever give you as intense of a high. Other forms such as swallowing it offer the same limited high that takes a few minutes to hit you. If you smoke meth the high is nearly instanntaneous. Additionally, as I mentioned, there is no bad taste and no pain at all. If smoking meth from a glass pipe the remaining portion of the drug will simply recrystalize and stick to the inside of the glass pipe once it cools to room temperature. This makes it terribly convenient to travel with- you could simply carry the pipe in your pocket and sneak into a restroom to smoke some without anyone being the wiser. Smoking also causes a fairly large percentage of the drug to enter your bloodstream at one time... this means the user can get more pleasure from a smaller amount of the drug. The convenience combined with the ability to do heavy doses can lead to faster and more gripping addiction. However, smoking is not the most addictive way. It is probably the most popular way, but injecting methamphetamine (or any injectable drug, really) is far more addictive. Of course, it has many drawbacks such as aversion to needles, difficulty obtaining syringes, necessary preparation time, and leaving track marks. Still, the intense high that it gives a user is such that one single time injecting the drug can cause severe addiction.

Your brain produces a lot of "drugs" that it uses as neurotransmitters for nerual communication. Addiction happens when you take a drug that is similar to something your brain/body creates, long enough for your body to stop producing its own chemicals because you introduce them into your body from external sources. When that introduction stops after your body has stopped producing its own chemcials, you get various types of side effects that only go away after you use more drugs, or your body begins to produce its own again. This is called Physical Addiction. Psycological addiction is different. NO drug is physically addicting after a single use, it can, however, be psychologically addictive. Physical addiction can come from any method of ingestion of drug, regardless of method (eating, snorting, smoking or shooting). And it can take days to weeks for your body to begin producing its own chemicals again after physical addction.

All great and informative answers, and kudos to you all, as well as the asking of the question participant, for to whom wasn't, then we wouldn't be here. I just wished to add a short side note about addiction. A compulsive personality, as well as ethnicity need to be considered into addiction potential, be that most drugs, weather it be alcohol, or Pot, or Meth. Meaning, that a main, and major contributor in conjunction with the substance will be the person themselves. It comes to why there are abusers, and just users, in each segment concerning the substance of choice. It always seems there are most people to whom have an ability to choose if and when they want that little extra in their step, while others we know are paranoid looking out the curtains every couple seconds, and/or hearing things, and to whom we see vacuuming out the fish tank, or who are trading appliances, and motorcycles, and just about anything to get them an eight-ball or an ounce of whatever. Ok now, remember that ole saying about an exception to every rule, well here it's called Heroin, and it's the grand-daddy of them all, and is a different story. Heroin, no matter how it's administered, will and does effect the entire body with the endorphin, Dopamine. It soothes and makes happy all your organs, especially the liver, and of course the master, the brain. Once your bod's been given a taste, it then needs, want's, and will go into shock if it don't get it again real soon like! So, everyone stay off that crap, as no one really has an ability to just throw it away without serious medical re-hab, and an irreversible hardship to your person. Cool jam here folks, and I'll see ya elsewhere! Peace!

All due respect, but none of these responses actually answer the question. Meth is the most addictive drug (yes more addictive than Heroin) because it releases a huge amount of Dopamine into the system (which opiates also do) and PREVENTS the re-uptake of the Dopamine (which means it prevents your body from making it's own Dopamine) Further, unlike Cocaine which leaves the body in 45 minutes, the chemicals from Meth can roam about the body for as much as 10 days. So if you party with Meth on the weekend, you are STILL ON IT by the time the next weekend rolls around! This longer "cycle" allows Meth to lure users into it's seductive trap. Even people who are very careful about not abusing drugs CAN be come addicted to Meth very easily almost without knowing it. Once it happens, it's too late. Although I have sampled and enjoyed other drugs in the past, I have made the decision not to use Meth. The risks far outweigh the benefits.