Lecture 4 - Susceptibility Models

Question 1

Exposure models

Answer 1

Addiction is caused by the drug and the neurological changes it promotes
- Withdrawal
- Opponent process

Question 2

Susceptibility models

Answer 2

Addiction due to individual vulnerabilities such as genetic, psychological or environmental factors
- Everyone not as likely to go through that process (specific people for specific reasons go from casual enjoyer to addict)
- Not everyone has an ‘addictive personality’ and not all drugs prompt addiction (so perhaps a little reductive)
- Likely a combination of the two e.g. can’t be susceptible if you’re not exposed in the first place

Question 3

Varying susceptibility

Answer 3

• If we were all equally susceptible, you’d see more homogeneous patterns
• Varying percentages of people try different drugs
• E.g. tobacco/nicotine quite common whereas heroin is quite low
• Not everyone becomes an addict
• Susceptibility varies across drugs

Question 4

Susceptibility factors: age and sex

Answer 4

• Age = peak time for experimenting with drugs is typically within late teens and early 20s (PFC still not finished – roughly mid-20s)
• Young people and men more susceptible to casual and addictive drug use

Question 5

Genetics

Answer 5

• Research suggests that 40-60% of addiction vulnerability is hereditary
• Specific genes affect how individuals respond to substances and their likelihood of developing addictive behaviours
• Includes potential impact on dopamine system e.g. fewer dopamine receptors (so want to try drugs as a form of negative reinforcement) or increased metabolism (need to drink more to get drunk so become addicted)
• Also drug aversion (e.g. allergic reactions to alcohol/drugs makes addiction less likely)
• Suggests predisposition, not a guarantee
• BIG issues with nature vs nurture

Question 6

Susceptibility factors

Answer 6

• Drug availability in local area
• Prevalence of drug use in local area
• Neighbourhood (population density, permanence, crime rate)
• Parental socioeconomic status
• Criminality in family
• Broken home
• Mental health of parents
• Parent-child attachment
• Peer group social norms
• Parent/sibling (attitude to) drug use
• Poor parenting style (e.g., abusive, negative, authoritative, inconsistent)
• Failure at school
• Genetics & role modelling
• Problems with correlation and causation, disentangling cause and effect, and mess and confounding variables (can’t look at one or two specific things)

Question 7

Tarter et al. (2003)

Answer 7

• Rare longitudinal study
• Followed children from age 10 to 19
• Split into high and low-risk groups (high risk = parent/sibling with substance use disorder)
• Matched across household income, parent education, parent drug use etc.
• Concluded that ‘Neurobehavioral Disinhibition’ was greater in the high-risk group and predicted (transition to) illicit drug use
• Neurobehavioral disinhibition was a comprise score of:
• Difficult temperament (inflexible, distractible),
• Conduct disorder, oppositional defiant disorder,
• Attention deficit hyperactivity disorder (ADHD),
• Depression,
• Disruptive behaviour disorders (teacher ratings),
• Tests measuring low executive cognitive function.
• Concluded: those at risk of drug (ab)use show disorganised behaviour, possibly stemming from abnormality in the frontal cortex, causing poor decision making
• De-emphasised things like environmental factors and parent/sibling use (there are more important factors that make people susceptible to drug use)

Question 8

Neurobehavioral disinhibition and the PFC

Answer 8

PFC plays a large role in drug using/seeking behaviour

Question 9

Phineas Gage

Answer 9

• Accident caused a large railroad spike to impale his head
• Severe frontal lesion
• Unreliable at work, showed callous disregard
• Preserved some intellectual function (e.g. memory) but planning ability became very poor
• Became an alcoholic and hyper-sexual
• Suggests PFC associated functions, such as decision making, long-term thinking, self-control, impulsivity and risk-taking tendencies influence addiction behaviour
• Caused a battery of PFC related tasks to develop

Question 10

IOWA gambling task

Answer 10

• 4 decks of cards, goal to win money
• Participants told all cards result in some level of reward
• Occasionally, choosing a card causes them to lose some money
• A and B are ‘bad decks’, C and D are ‘good decks’
• Decks are rigged – 2 decks give a higher upfront reward and 2 decks give lower
• Most people can figure this out but lots of people with frontal lobe damage can’t do this well
• Bechara et al. (2000) = patients with PFC lesions do much worse than normal because they opt for immediate gains despite higher future losses

Question 11

PFC and risk decision making

Answer 11

• Deakin et al. (2004) = general impression is that maturity increases over age until about 20-25
• Suggests that susceptibility for drug use amongst younger people might, in some cases, be due to PFC underdevelopment
• Young people engage in more risky decision behaviour, whilst older people are more methodical and calculated in their risk-taking behaviour
• In the IOWA gambling task, those who frequently select the high reward decks despite the net loss of points:
• With Frontal lesions/damage
• In Adolescence
• With a Conduct Disorder
• With ADHD
• With Schizophrenia
• Who indulge drugs of all classes

Question 12

Cause and effect?

Answer 12

• Risky decision making seen in high-risk children before any drug use
• Risky decision making predicted the onset and magnitude of drug use
• Suggests PFC damage or dysregulation is a major susceptibility factor for becoming a drug user
• Alcohol is one of the worst things that can damage the PFC due to the damage caused by withdrawal (they’re susceptible to seizures etc.)
• People with PFC abnormalities/dopamine abnormalities are more likely to take part in drug taking behaviour – cause and effect cycle

Question 13

Risky decision making

Answer 13

• Perseveration in selecting the bad decks in the Iowa task could be due to several aspects of risky decision making, all of which can predict drug use:
• Reward hypersensitivity (overactive mesolimbic system) = everything in life must be motivated by some kind of reward, maybe addicts are super sensitive to reward
• Reward hyposensitivity (insensitivity) = conditioned tolerance or negative reinforcement seeking to alleviate feeling of not feeling good
• Punishment insensitivity
• Faulty error detection

Question 14

Punishment insensitivity: clinical relevance

Answer 14

• DSM Drug Dependence Criteria:
• (1) Continued use of drugs even though known to cause trouble with family or friends.
• (2) Job/study troubles because of drug use - missing too much work, being demoted/not doing work well, being suspended/losing a job, being expelled/ dropping out of school.
• (3) Continued use of drugs even though known to cause a health problem or make a health problem worse (e.g., lung cancer, liver disease, coke nose…)
• Important clinically because it’s the clinical criteria
• Insensitivity to these punishments may be because they creep up over time and require years of drug misuse

Question 15

Punishment Insensitivity

Answer 15

• Deroshe-Gamonet et al. (2004)
• Trained the rats to give themselves coke, then put them through withdrawal
• Reintroduced coke and provided a cue that previously predicted coke delivery, some relapsed
• Introduced a small experimental punishment (small shock) for relapsed rats
• Some animals keep wanted the coke even when paired with a shock (very strong punishment insensitivity)

Question 16

Error detection

Answer 16

• Addicts may have full knowledge of the averse consequences of their drug taking, but just not be able to use this knowledge to correct their behaviour
• Event related potential (ERP) used to measure the responses of cocaine addicts to errors in their performance
• Simply unaware of negative effects of drugs (see/hear it but not sinking in, so can’t use that information to influence future behaviour)
• Franken et al. (2007) – flanker task (task to identify the central letter)
• Cocaine addicts showed a reduced frontal activity in response to errors (suggesting reduced neural sensitivity to errors) and less post-error improvement in performance
• Suggests that addicts may have less knowledge of the adverse consequences of their behaviour, and so less ability to use this knowledge to modify their behaviour