Risk factors for drug use

Question 1

What do we know about adolescence and drug use?

Answer 1

> Initiation to drug use typically occurs during adolescence
- experience is normative

> A minority escalate to frequent or problematic drug use

> Adolescence = peak period for onset of abuse and dependence

> Very few people who don’t initiate drug use in adolescence will develop abuse or dependence

Question 2

What does animal research show on the sensitivity to drug exposure in adolescents vs adults?

Answer 2

Adolescents are

> Less sensitive to

• aversive effects of acute alcohol intoxication
• sedation, hangover, ataxia

> More sensitive to

• alcohol’s effects on social facilitation
• alcohol disrupting spatial memory

-> adolescent brain is uniquely sensitive to drug exposure

Question 3

When talking about cause of drug use, what is a cause?

Answer 3

An event / occurrence that increases the probability of the effect

• e.g. cigarette smoking increases the probability of lung cancer but not everyone who smokes develops it

Question 4

What are the six categorised risk factors for drug use according to Hawkins et al. (1992)?

Answer 4

1. Laws and norms
   (e. g. economic deprivation)
2. Neighbourhood
   (e. g. disorganisation, alcohol outlets)
3. Peers and school
   (affiliating with drug using peers is a prominent risk factor)
4. Family
   (conflict, low bonding)
5. Early onset of drug use
   (increases risk of escalation)
6. Individual
   (e. g. early and persistent behavioural problems)

Question 5

What are the effects of specific risk factors?

Answer 5

Risk factor effects independent of the effects of potential confounding covariates

Question 6

Why is longitudinal/prospective research valuable in identifying risk factors for drug use?

Answer 6

• Increases accuracy of the timing of events

- Can access large number of potentially confounding covariates

Question 7

What is the Christchurch health and development study (Fergusson et al., 1996)?

Answer 7

Longitudinal study in New Zealand on childhood sexual abuse and drug abuse/dependence

> Birth cohort: 1265 children born May-August 1977

> Data collected at:

• birth
• 3 months
• one year
• annual interval until 16
• ages 18, 21, 25, 30, 35

> Reports from:

• parents
• self-reports
• teachers
• significant others
• official records (hospital and police)

Question 8

What were the findings of the Christchurch health and development study (Fergusson et al., 1996)?

Answer 8

> Approx. 1/6 of cohort has been exposed to childhood sexual abuse (CSA) before age 16

> 40% of young people who had experienced CSA with intercourse reported history of alcohol/drug abuse/dependence
(vs. 12.5% for those who didn’t experience CSA)

> Strong associations between CSA (esp. intercourse) and risks of alcohol/drug abuse and dependence
- even after control of wide range of potential covariates

Question 9

Which elements need to be considered when identifying risk factors?

Answer 9

• Effect size
• Relative risk
• Base rate of exposure to risk factor within the population

Question 10

What is the population attributable risk (PAR)?

Answer 10

Number/proportion of cases that would not occur if the factor was eliminated

Question 11

What does the attributable risk depend on?

Answer 11

• Prevalence of the risk factor

- Strength of its association with the outcome

Question 12

What was the population attributable risk (PAR) between childhood sexual abuse and alcohol/drug abuse or dependence, in the Christchurch health and development study (Fergusson and Horwood, 2001)?

Answer 12

10% of drug abuse would not occur if childhood sexual abuse (i.e. risk factor) was eliminated

Question 13

What are protective factors (Rutter, 1985)?

Answer 13

Factors that reduce risks within a high risk group

• these factors may not be generally related to risk throughout the population

Question 14

What are the elements underlying risks in a group?

Answer 14

Relationship between:

• risk factors
• protective factors
• risk of adverse outcomes

Question 15

What were the identified protective factors in the Christchurch health and development study?

Answer 15

Those who did not develop adjustment difficulties (including those who experienced CSA and those who didn’t) had:

• fewer affiliations with delinquent peers
• more caring/supportive parenting

Question 16

What did the latent class analysis reveal in the Christchurch health and development study?

Answer 16

Multiple problem teenagers were more likely to experience each of the disadvantageous family features

Question 17

What did the analysis on the accumulation risk reveal in the Christchurch health and development study?

Answer 17

Accumulation of risk places individuals at particular risk of alcohol and drug abuse, behavioural problems

Question 18

What are the research designs included in the identification of genetic factors for drug use?

Answer 18

• Adoption studies
• Twin studies
• Extended family designs
• Approaches incorporating measured genes

Question 19

What did the Danish adoption study reveal (Goodwin et al., 1973) about the environmental and genetic influences on alcohol dependence?

Answer 19

> Intergenerational transmission of alcoholism is determined by genetic, not the environment
- correlation between biological parents and offspring > to correlation between adoptive parents and offspring

> Genetic effects equally important for both women and men
- however, lower base rate of alcohol problems in women limits statistical power

Question 20

What are the limitations of adoptions studies?

Answer 20

> Prenatal environment and early environment (pending on age of adoption)
-> potential wrong attribution to genetic influences

-> associations between biological parents and offsprings might be partially driven by environmental influences

> Selective placement

• could inflate association between parents and offspring
• > wrong attribution to genetic influences

Question 21

What is a selective placement in adoption?

Answer 21

When children are adopted in families considered similar to their biological families

Question 22

What is a popular research strategy to separate the influences of genetic and environmental effects?

Answer 22

Twin studies

Question 23

What makes monozygotic (“identical”) twins?

Answer 23

• Fertilisation of single egg by single sperm

- Share 100% of genetic material

Question 24

What makes dizygotic (“fraternal”) twins?

Answer 24

• Independent fertilisation of two eggs by two 2 sperms

- Share 50% of genetic material

Question 25

In a twin study, what is suggested if the correlation of behaviour between monozygotic twins is superior than that of dizygotic twins (rMZ > rDZ)?

Answer 25

Genetic factors are important

Question 26

In a twin study, what is suggested if the correlation of behaviour between dizygotic twins is superior than half of the correlation between monozygotic twins (rDZ > 1/2rMZ)?

Answer 26

Growing up in the same home is important (shared environment)

Question 27

In a twin study, what is suggested if the correlation of behaviour between monozygotic twins is inferior to 1 (rMZ < 1)?

Answer 27

Non-shared environmental factors are important

Question 28

What does the structured equation modelling analysis consist of in a twin study to determine the influence of drug use?

Answer 28

> Large data sample of twin pairs

> Identify the extent to which a specific behaviour (drug use) is influenced by:

• additive genetic (A)
• shared environment (C)
• non-shared environment (E)

Question 29

What did the Australian twin study of Lynskey et al. (2002) reveal on the explanation of the variance in cannabis dependence?

Answer 29

> Approx. 45% of variance in cannabis dependence explained by additive genetic factors

> Approx. 20% explained by shared environment

Question 30

What did the meta-analysis of heritability estimates of problematic cannabis use by Verweij et al. (2013) show?

Answer 30

> More than 50% of the variance in problematic cannabis use is explained by additive genetic factors
- in both males and females

> Environmental factors are significant

Question 31

What did the worldwide twin studies show on the heritability estimates of drug dependence?

Answer 31

30-70% of variance in drug dependence (alcohol, nicotine, other illicit drug use disorders) explained by heritability

Question 32

What is often overlooked in research and drug dependence?

Answer 32

Addiction is a multi-stage process

Initiation -> Regular use -> Heavy use -> Dependence/addiction)

Question 33

What happens to the rates of heritability and twin environment factors when studying addiction as a multi-stage process?

Answer 33

> Initiation stage

• lower heritability (30-50%)
• more effect of twin environment (30-50%)

> Dependence stage

• higher heritability (up to 70%)
• no effects of twin environment

Question 34

According to the Virginia twin study (Gillespie et al., 2009), is cannabis availability influenced by genetic factors?

Answer 34

Yes

Question 35

According to the Vietnam vets twin study of (Tsuang et al., 1998), is there a common vulnerability to addiction across different drug classes?

Answer 35

Common vulnerability
AND
Common genetic vulnerability

Question 36

What does the high correlation between two genetic factors influencing licit and illicit drug dependence symptoms suggest (Kendler et al., 2012)?

Answer 36

Large overlap in genetic influences between illicit and licit substances
(environmental influences are very similar)

Question 37

What has been shown on the association between genetic influences, conduct disorder and externalising behaviours (Dick and Agrawal., 2008)?

Answer 37

Genetic influences are correlated with anti-social behaviour or externalising problems

Question 38

What have twin studies demonstrated on the liability to drug abuse/dependence?

Answer 38

Substantial component of this liability to drug abuse/dependence is influenced by heritable factors

Question 39

What have twin studies demonstrated about the heritable influences on different stages of drug use (opportunity, duration, abuse/dependence)?

Answer 39

These heritable influences on different stages of drug use overlap

Question 40

What have twin studies demonstrated about the heritable influences on abuse/dependence on different drugs?

Answer 40

These heritable influences on different drugs overlap

Question 41

What have twin studies demonstrated on the heritable influences on drug abuse/dependence and externalising behaviours?

Answer 41

Heritable influences on drug abuse/dependence overlap with heritable influences on externalising behaviours