In general, I'd concede that what you say is pretty accurate. Benzos are rated as highly addictive, however it is a personal thing and I find it not too difficult at all to come off them when I have taken them for a while, ie I get a couple of sleepless nights and that's more or less it. There again, I never had a problem stopping smoking, yet some people really struggle.

While codeine withdrawal isn't as bad as heroin or morphine or methadone, it is not pleasant, and it isn't true to say you can easily get more. If that's the kind of codeine you're taking then I suppose addiction/withdrawal isn't a huge issue. I'm talking about the hydrocodone type drugs, which are just codeine, but tweaked in a way to make them much more potent, and potentially much more addictive.

Methadone/heroin/morphine etc are usually controlled when taken regularly. Either they have to be bought on the black market or they're prescribed in a very controlled way. The trouble with dhc is that you can be given a large amount, meant to last a month, use the lot in a fortnight and then go through hell before you can obtain any more! In that way withdrawal can be worse than with a stronger opiate, simply because the potential for abuse is so much greater. The potency of dhc is gradually sinking in as far as the medical profession is concerned, and dhc is now a Class B drug and more tightly controlled, ie every pill has to be accounted for and no more than a month's supply can be given at any one time. Possession is not in itself an offence, but selling is.

Yes, dhc is sometimes used as a replacement for morphine etc to wean people off because it is a short acting drug and the withdrawal symptoms do generally clear up after about 5 days. However heroin, methadone and morphine are roughly as long lasting, but within a fortnight you'd be over the main symptoms.

Withdrawal happens because opiates suppress production of noradrenaline, so the body goes into overdrive producing it when you take the drug. Then when you stop suddenly, it has to compensate and this takes a few days. That's the unpleasant (but not dangerous) "cold turkey". Catapres (clonidine) can help because it suppresses noradrenaline and addicts are sometimes offered patches which release the substance gradually. Clonidine is a beta blocker.

There's a secondary withdrawal which happens because opiates are a much more efficient producer of endorphins than the body's natural mechanism, so the body's production of this is reduced drastically when taking the drug. Endorphin is what makes us feel pleasure out of things in life, and when this is not being produced in sufficient quantities, it's as if the body's "pleasure thermostat" has been turned down and the result is depression and the inability to find pleasure in the normal everyday events in life.

Your body does adjust, but particularly after long term opiate use, this can take months and anti depressants are often used as a short term aid.