> Lars,
>> The definition you've applied to marijuana "addiction," warm and fuzzy
> though it may be is not the classical Pharmacological definition of
> addiction, where absence of the addictive substance has measurable
> physiological effect which often lead to the behaviors described in your
> definitio0n. Consider caffeine. Chronic use causes dependence
> (addiction), and withdrawal symptoms emerge if the addiction is not
> satisfied. However, you'd be hard pressed to define it as addictive using
> the psycho-babbelian terms you posted.
Actually, this definition is totally obsolete. No one who seriously works
in the addiction field (except for MDs) believes that physical dependence
(defined by a marked withdrawal syndrome upon cessation of the drug)
and addiction are the same thing anymore. This theory is antique,
and actually dates back to the civil war, now known as the
"Negative Reinforcement Model", and is largely based on medical experience
with opiates and barbiturates.
In this model, people take drugs to avoid the unpleasant consequences
of withdrawal. The problem with this theory (which everyone knows) is
as follows: because withdrawal determines the size of addiction, if this
theory was right, the drugs which produce the largest dependence should
produce the largest addiction:
Largest Smallest
Barbiturates Alcohol Opiates Cocaine Amphetamine
Obviously, the problem with this theory was more than apparent by
the late 1960s, when cocaine and amphetamine addiction were prevalent
(and still are) and people started arguing that they were both
in fact more addictive than other drugs. Lots of other problems
made the negative reinforcement (withdrawal) model of addiction
untenable, including:
1) you can treat withdrawal, and people just relapse months later
anyway
2) the model can't deal with how the dependence is initially established.
this is because it was meant to deal with medically produced
addictions
3) what's worse, is recent studies even have shown that people who develop
dependence in a hospital to strong opiates still don't end up
being addicts.
So the final "ruling" of -RF was as follows:
a. Withdrawal/Dependence is not necessary for addiction:
cocaine/amphetamine, which produce only a mild dependence, but
a robust addiction
b) Withdrawal/Dependence is not sufficient for addiction:
oxymetazoline, the ingredient in nose drops, produces a very
potent dependence, but no addiction. There are hundreds of
examples of drugs like this, but people will not give up their
family quit their job and move onto the street for nose drops.
This is not to say that dependence can't motivate behavior, it's
just on a different scale than addiction.
This led to a revolution within the field, namely, the Positive
Reinforcement Model, which had been around for years, but didn't
have good empirical evidence. basically the model is that addiction
is due to some pathological positive reinforcement process. This model
emphasizes compulsive drug-taking, compulsive drug-seeking, and relapse
after withdrawal. This is a modern defintion of Addiction:
Addiction is a behavioral pattern of drug use characterized by compulsive
drug-taking, the securing of its supply (compulsive drug-seeking), and
a high tendency to relapse, even long after withdrawal.
So how can you measure +RF? Well, you set up a rat to bar press for
the drug, and you can compare how much it will bar press for different
drugs (a model of compulsive drug-taking)
Likewise, you can look at conditioned place preference, which
is a model of compulsive drug seeking. In each case, you find very
high levels of reinforcement in drugs which actually produce addiction,
and their ranking corresponds to real world addiciton:
High Low
Amphetamine Heroin Cocaine Nicotine Codeine Barbiturates
More importantly, the model can discriminate between highly addictive
opiates (e.g., Heroin, Fentanyl) and those which do not produce
addiction (but do produce dependence), e.g., Codeine. Marijuana
is not reinforcing, nor is LSD.
Anyway, I'm tired now,
Stephan
