From a friend's blog:
Psychotropic drugs are fundamentally destructive to a person who uses them, and anyone who does use them should be trying to figure out a way to get off of them.
That's a judgement call that might be valid for yourself, but don't pretend to know what's better for other individuals – it is harmful to your well-meaning premise (presumably that individuals should be ruled by self-determination instead of enslaved to external forces).
The body develops immunity to the beneficial effects of any drug, eventually requiring stronger and stronger doses, but never does so to the side effects.
This is a false, though oft-repeated, generalization. Every mind-altering substance is different in its effects, and only a few actually fit into that box that you've drawn out.
There are 3 components to substance addiction; reinforcement/habituation, withdrawal, and tolerance. Anything pleasurable is reinforcing: chocolate, sex, alcohol, etc. It becomes a habit when the person does not control their impulses to partake. Some drugs are extremely reinforcing to the point where natural rewards are irrelevant, and others not so much, complementing natural rewards instead of displacing them with drug cravings. Withdrawal is a combination of psychological and physical effects that occurs when a habitual user attempts to quit. You might be surprised to learn that alcohol withdrawal can actually kill the subject; no other substance withdrawal is as physically brutal. Opiates and tranquilizers also have very unpleasant withdrawal effects. Withdrawal causes continued administration of the substance to have a positive reinforcing effect proportional to the severity of withdrawal symptoms. The last criterion, tolerance, is a phenomenon that is most closely associated with opium derivatives. This is unfortunate, because coupled with the unpleasant effects of opiate withdrawal, it is responsible for the downward spiral that habitual opiate users tend towards. This effect is present with alcohol too. Most other substances that exhibit an effect similar to tolerance are actually simply saturated in the body – ingesting more has no effect until the body eliminates what is already inside. Since withdrawal symptoms for most substances are mild to non-existent, the user is inclined to moderate their usage or quit instead of OD-ing. The effects of tolerance in the absence of withdrawal thus have a negative reinforcing effect on continued administration of the substance; the user simply becomes bored or burned out.
So what's a beneficial effect? By definition, all recreational drugs produce pleasurable effects (such as psychedelic, painkilling, sedative, etc) to at least some users, or they would not be used. Does a beneficial effect imply a pleasurable effect in this context then? It is a false statement that the pleasurable effect of all drugs decreases over time (i.e., that all drugs foster tolerance). Each drug is unique in its effects and its addiction potential according to the habituation/withdrawal/tolerance characteristics of the substance. So maybe beneficial effect was meant in general, relative to the user's life. The user is responsible for evaluating his/her use and the associated consequences, just like with legal drugs such as alcohol, nicotine, and caffeine. We aren't doing future adults any favors by propagating falsehoods and inaccurate generalizations. And we aren't doing ourselves any favors providing advice to friends that is based on false premises.
Even worse is basing public policy on false premises. Even worse than that is propping up unconstitutional actions of the federal government because drugs are felt to be some kind of special case. You would think a small-government advocate would get this, but Republicans are just way too hung up on the drug issue. As a result, they willfully contribute to the imbalance of power in this country and the imprisonment of peaceful individuals who refused to follow laws that are wrong.
Prohibition causes more harm than drugs cause. This is not the Great Society anymore where we can use public policy to meld individual desires to conform to some utopian vision. Drugs are real, people like them, and people sell and use them despite the law and despite the dangers of an unregulated black market. Only accepting that reality will bring us closer to ideal policy on the issue.