Lecture 3 - Exposure Models

Question 1

How many people try addictive drugs?

Answer 1

• Researched by:
• NIDA = National Institute on Drug Abuse
• UK Data Service
• NCDAS = National Centre for Drug Abuse Statistics
• Crime Survey for England and Wales
• Interview and questionnaire provide issues for data collection (e.g. household reporting – being filled out by an adult who may not know the half of it)
• According to earlier British Crime Surveys (BCS):
• In 1996, around 30% of adults (16-59) had tried illegal drugs at some point in their lives
• In 1998, this increased slightly to around 32%
• By 2000, the figure was around 33% (1 in 3 adults)
• Lag because longitudinal studies are expensive and take time (also if effects are stable, you’re less likely to get funding for additional ones)
• Spike in 1985 = crack epidemic coming to an end

Question 2

Patterns of drug use now

Answer 2

• Lifetime statistics:
• UK – (Crime Survey for England and Wales 2022) suggests around 38% of adults aged 16-59 have tried drugs
• USA – the National Survey on Drug Use and Health (NSDUH) 2022 reports that over 50% of Americans aged 12+ have tried an illicit drug at some point in their lives
• Past year statistics:
• UK – in 2024, about 8.8% of adults (16-59) reported using drugs in the past year
• USA – in 2022, about 17.3% of Americans (12+) reported using illegal drugs in the past year
• Drug use stable over 25ish years, but drug deaths are going up (e.g. changes in manufacturing, cut with other drugs, becoming stronger etc.)
• Most people aren’t daily users
• US and UK follow similar patterns
• Differences may be due to data collection and shifting perspectives surrounding drugs

Question 3

Takeaways

Answer 3

• Drug use is relatively stable over time
• Most illicit drug use isn’t daily
• Most drug use is by younger people
• Most drug use is by less affluent people
• Most drug use is by men
• Use patterns vary by drug and age
• Some drugs are popular and stay popular and some don’t (due to how its exported, produced, politics or general crack downs on it) e.g. PCP and salvia
• Mostly weed – people more likely to report using weed (and attitudes towards it changing e.g. legalisation)
• Smoking in youth decreased a lot over time
• Vaping increased over time (2014 onwards)
• Alcohol use in young people decreasing over time
• Alcohol use in 16-24 year olds relatively stable

Question 4

Conditioning primer

Answer 4

• Pavlovian conditioning
• UCS + NS
• CS -> CR
• Extinguish associations to help addiction

Question 5

Exposure models

Answer 5

• What keeps people hooked once they’ve started taking it?
• All people are at risk of becoming addicted to drugs given sufficient exposure
• Drugs interact with and change the brain
• Brain changes create continued motivation to use the drug
• Models differ in their explanation as to what sort of changes drugs produce in the brain and what sort of motivation drives subsequent drug use
• Exposure varies by drug e.g. heroin might be addictive after 1 try, whereas weed doesn’t typically introduce the chance of addiction until you’ve become a daily smoker
• Bardo et al. (1996)

Question 5

Exposure models: withdrawal

Answer 5

• Addicts continue to use the drug in order to avoid withdrawal
• Withdrawal = the physical and psychological symptoms that occur when a person reduces or stops intake of a substance they are dependent on
• These symptoms can vary widely in severity and type, often leading to cravings, anxiety and distress e.g. irritability, sweating, depression/dysphoria, tremors, trouble sleeping
• Most extreme in opiates (ideally under medical supervision to withdraw)
• Withdrawal = very aversive (real barrier to quit) – a form of negative reinforcement
• The initial high exhausts the reward/pleasure regions of the brain, and once the drug wears off the user goes into withdrawal

Question 6

Relapse

Answer 6

• Withdrawal models don’t account for withdrawal
• Stopping drugs under medical supervision doesn’t necessarily result in long term abstinence
• Drug users often relapse despite having undergone supervised withdrawal from drugs
• Wikler (1948) – proposed that withdrawal can be triggered by external cues e.g. not seeing dealer in rehab etc.
• Classical Pavlovian conditioning key mechanism here:
• Environmental stimuli, such as the addict’s bedroom or living room, are consistently paired with withdrawal
• Through Pavlovian conditioning, stimuli enter into learned associations to become triggers for withdrawal symptoms
• Subsequent exposure to these cues is then sufficient to elicit withdrawal, and thereby precipitate relapse
• Thus conditioned withdrawal can explain relapse following primary withdrawal
• Conditioned response/reflex
• Conditioned withdrawal (O’Brien et al., 1977) - took human volunteers (opiate addicts on methadone). They experimentally induced a withdrawal using an opiate blocker and they’d start to feel pretty rough
• Compared with the base line, the people with the blocker & conditioned cue (tones) were showing higher symptoms of withdrawal. Then, at a test phase, the odor also inspired the skin temp drop (like Pavlov’s dog salivating)
• Anecdotal reports from relapsed drug users suggest things are not always as predicted e.g. by contexts in which withdrawal had occurred most frequently e.g. bedroom
• ‘Trace’ of CS – lingering effect of stimulus
• i.e., most people report the most cravings while out and about, not at home. Issues with availability (at home vs. out and about). Maybe the triggers more likely to prompt us are the ones we’re less exposed to (not at home)
• People can associate cues with outcomes over a delay or a trace – this might explain some of the complexity.

Question 7

Can’t all be aversive

Answer 7

• People also actively like drugs (positive reinforcement – seek nice thing)
• Midbrain dopamine cells increase activity when humans or animals detect or consume both natural rewards (food, water, sex) and drugs of abuse (nicotine, cocaine, heroin)
• Suggests that drugs of abuse hijack the brain substrate for reward/pleasure and are consumed because drug taking is positively reinforcing
• DA exhaustion followed by withdrawal

Question 8

Opponent process model

Answer 8

• Initial positive experience = positively reinforcing drug use
• Subsequent negative experience = where the body attempts to restore balance, leading to a negative effect (withdrawal)
• With repeated use, the initial positive effects become weaker (tolerance) and the negative effects become stronger
• Creates a cycle of addiction
• Solomon & Corbit (1973)
• Fear conditioning
• Positive (wanting to be high) vs negative (wanting to avoid withdrawal). After time, the 2nd response starts to take over

Question 9

Opponent process model - tolerance

Answer 9

• “after repeated use of a drug, the body’s response to the substance diminishes over time. This means that higher doses of the drug are required to achieve the same effect that was initially produced at lower doses. Tolerance can develop to various effects of the drug, including its therapeutic effects, side effects, or both” – ASAM

Question 10

Pharmacodynamic tolerance

Answer 10

Occurs when the drug’s effects at the cellular or receptor level become less pronounced

Question 11

Pharmacokinetic tolerance

Answer 11

This arises when the body becomes more efficient at metabolising or eliminating the drug

Question 12

Conditioned tolerance

Answer 12

• High heroin dose given to heroin tolerant rats:
  Deaths by Environment (%)
• Novel = 96%
• Usual = 64%
• Same amount of heroin in new environment killed rats
• Environmental cues associated with drug taking can elicit a ‘drug opposite’ response
• Drug opposite response may be aversive and motivate drug taking to alleviate this state (negative reinforcement).
• Siegel (1983)

Question 13

Positive conditioning

Answer 13

• Hogarth et al. (2010) data consistent with hypothesis drug cues prime drug taking by reminding the addict of the positive appetitive qualities of the drug (not by eliciting an aversive state)
• Positive symptoms of addiction associated with stimulus

Question 14

Conclusions

Answer 14

• Drug use is relatively stable over time, with some drugs being more popular than others
• Drug taking is motivated by a complex set of mechanisms, thought to change as the drug user progresses from being ‘casual’ to addicted
• Initially, drug use is driven by positive reinforcement, followed by negative
• Associated environments can prime drug taking and tolerance