Dependence and Dependence and Addiction!!Addiction!!

Psychology 3506Psychology 3506

IntroductionIntroduction

When people first thought about it When people first thought about it (and until relatively recently) drug (and until relatively recently) drug taking behaviour just seemed oddtaking behaviour just seemed odd• Not avoiding painNot avoiding pain• Doesn’t affect all people the same wayDoesn’t affect all people the same way• You don’t ‘need’ itYou don’t ‘need’ it

Aha! You must be an immoral pig, Aha! You must be an immoral pig, probably with little willpower. You probably with little willpower. You are a bad person you junkie lowlifeare a bad person you junkie lowlife

The Disease ModelThe Disease Model

Oh perhaps it is not a problem with Oh perhaps it is not a problem with your character or moralityyour character or morality

Ahh, yes, it is a diseaseAhh, yes, it is a disease• Or a disorder as we say todayOr a disorder as we say today

Started with alcoholismStarted with alcoholism What is the disease mechanism?What is the disease mechanism? But it is genetic!But it is genetic!

• So whatSo what

Physical Dependence ModelPhysical Dependence Model

Withdrawal (from morphine) caused Withdrawal (from morphine) caused by ‘autotoxin’by ‘autotoxin’

Found to be lacking, but, the idea Found to be lacking, but, the idea stuck. stuck.

Indeed, still VERY popular Indeed, still VERY popular Accounts for the ‘abnormality’ of it allAccounts for the ‘abnormality’ of it all Can be combined with the disease Can be combined with the disease

modelmodel

Physical Dependence ModelPhysical Dependence Model

Only Depressants?Only Depressants?• Tatum and Seevers (1931) added Tatum and Seevers (1931) added

habituationhabituation Problem is, that stimulants, for the Problem is, that stimulants, for the

most part, don’t produce withdrawal most part, don’t produce withdrawal symptomssymptoms

Hmm, Let’s invent a new idea!Hmm, Let’s invent a new idea!

Psychological DependencePsychological Dependence

When you need a drug, but don’t When you need a drug, but don’t need a drugneed a drug

When you crave a drugWhen you crave a drug• CircularCircular

Biggest problems:Biggest problems:• Continual abuse with drugs that do NOT Continual abuse with drugs that do NOT

produce withdrawalproduce withdrawal• Addiction without dependenceAddiction without dependence

Positive Reinforcement ModelPositive Reinforcement Model

People used to think you couldn’t get People used to think you couldn’t get animals addictedanimals addicted• Not moralNot moral• Can’t get the diseaseCan’t get the disease

CatheterCatheter Work for drugWork for drug

• (Thompson and Shuster, 1964)(Thompson and Shuster, 1964)

How does it work?How does it work?

Seems circular, until you realize that Seems circular, until you realize that we know what a reinforcer is not just we know what a reinforcer is not just from operational definition, but from from operational definition, but from physiologyphysiology

Dopamine hypothesisDopamine hypothesis• VTA -> MFB -> ACCVTA -> MFB -> ACC

Morphine to PVG leads to Morphine to PVG leads to dependence, to ACC, does not!dependence, to ACC, does not!

Animals and us aren’t so different Animals and us aren’t so different after all….after all….

Shuster’s other workShuster’s other work• Rats will work for drugs not causing withdrawalRats will work for drugs not causing withdrawal• Rats will work for drugs without dependence!Rats will work for drugs without dependence!

Is hard to get them to take things orally Is hard to get them to take things orally thoughthough

Pickens and Thompson (1968) found that Pickens and Thompson (1968) found that drug use follows the laws of learning!drug use follows the laws of learning!

So you are saying it is just So you are saying it is just conditioning?conditioning?

Well, umm YesWell, umm Yes Explains the paradox of positive and Explains the paradox of positive and

negative effects of drugsnegative effects of drugs Choice in taking a drug depends on Choice in taking a drug depends on

other available reinforcersother available reinforcers• Hayman says it follows the matching Hayman says it follows the matching

law!law!

Behavioural EconomicsBehavioural Economics

Basically applying the ‘laws’ of Basically applying the ‘laws’ of economics to behaivoureconomics to behaivour

Elasticity of demand is a biggieElasticity of demand is a biggie Caroll’s (1993) data on PCPCaroll’s (1993) data on PCP

• Demand changed from elastic to Demand changed from elastic to inelastic, depending on price. inelastic, depending on price.

• Inelastic at low pricesInelastic at low prices

Carroll (1993)Carroll (1993)

Different prices Different prices (number of responses) (number of responses) for drugfor drug

Demand inelastic, Demand inelastic, until it gets expensiveuntil it gets expensive

If there is something If there is something else available else available (saccharin in this (saccharin in this case) the monkeys will case) the monkeys will switch to it switch to it (substitution)(substitution)

ConclusionsConclusions

Drug taking behaviour can be easily Drug taking behaviour can be easily modeled using animalsmodeled using animals• We all follow the laws of learningWe all follow the laws of learning

Not all drugs will be self administered Not all drugs will be self administered by all animals, so be carefulby all animals, so be careful