Addiction and Disease Models

What are the three broad historical perspectives on addiction?

Immoral behavior/character flaw, disease, and maladaptive behavior/learned habit.

What perspective is the focus of Chapter 2?

Disease models of addiction.

What are general features of disease models of addiction?

They tend to decrease stigma, emphasize abstinence, view addiction as a chronic condition, and are common in treatment communities such as AA/NA and rehabilitation centers.

How do disease models generally affect the way people with addiction are treated?

They shift the focus away from punishment and toward helping and treating the person.

How do AA and medical communities differ in their disease perspectives?

AA emphasizes spiritual aspects of recovery and views addiction as LIKE a disease, while medical models emphasize neurobiology and genetic susceptibility and view addiction AS a disease.

What is central to AA's conceptualization of recovery?

A spiritual emphasis, including a Higher Power.

What is central to the medical conceptualization of addiction as a disease?

Brain/neurobiological processes and genetic susceptibility.

Is there only one medical disease model of addiction?

No. There are multiple disease models that emphasize different parts of the addictive process.

Are the different medical disease models necessarily in conflict?

No. They are generally complementary because they focus on different aspects of addiction.

What are two major types of medical disease models discussed in Chapter 2?

Susceptibility models and exposure models.

What does the susceptibility model emphasize?

Genetic factors that influence a person's vulnerability to addiction.

What does the exposure model emphasize?

The effects of substances and their chemical influence on the brain as causes of addiction; this includes the 'brain disease' perspective.

Why are disease models controversial?

Although heavily endorsed, researchers have questioned their validity and/or specific assumptions within them.

According to the earliest disease model, what is addiction?

A primary, chronic disease.

According to the traditional disease model, is addiction an attribute of the person or the drug?

The person.

According to the traditional disease model, what causes substance use?

The underlying addiction causes the substance use.

According to the traditional disease model, what happens if a person does NOT have the disease?

Alcohol or drugs supposedly will not become a problem for that person regardless of how much they use.

What is the 'allergy' model of addiction?

The idea that individuals with the disease react differently to a substance, similar to an allergy, and only those with this disease or 'allergy' can become addicted.

According to AA/allergy models, is drinking itself the disease?

No. Drinking or substance use is considered a symptom of the underlying disease.

How is addiction characterized by AA/allergy disease models?

As a chronic, semi-permanent state.

What is physiological dependence?

Neuroadaptation to the presence of a drug, involving processes such as tolerance and withdrawal.

What is tolerance?

Needing increasingly more of a substance over time to achieve the same desired effect.

When does tolerance tend to develop?

With regular substance use.

Is tolerance required for an AUD or SUD diagnosis?

No. It is one possible symptom but is not required.

What is acute withdrawal?

Symptoms that occur when a substance leaves the body after a prolonged period of use.

What factors affect withdrawal symptoms?

The particular substance and the person's level of use.

What are examples of withdrawal symptoms listed in the slides?

Insomnia, anxiety, and in severe cases, death.

Is withdrawal required for an AUD or SUD diagnosis?

No. It is a possible symptom but is not required.

What disease model focuses on genetic origins of addiction?

The susceptibility model.

Is there evidence for familial transmission of addiction?

Yes. Research suggests hereditary influences contribute to addiction risk.

What evidence supports genetic influences on addiction?

Animal research, twin studies, and evidence that genes and environments jointly shape human behavior.

What is behavior genetics?

The area of psychology that applies genetic methods and research designs to study the nature and origins of individual differences in human and animal behavior.

What are the two broad types of behavior-genetic studies discussed?

Quantitative genetic studies and molecular genetic studies.

What are examples of quantitative genetic studies?

Twin studies and adoption studies.

What do quantitative genetic studies estimate?

The proportion of variation in a trait that is associated with genetic and environmental influences.

What do molecular genetic studies examine?

Relationships between genomic regions or specific genes and behavior.

What is genotype?

A person's unique arrangement of genes.

What is phenotype?

Observable traits or individual characteristics resulting from the interaction between genotype and environment.

Genotype vs. phenotype

Genotype = genetic makeup; phenotype = characteristics resulting from interactions between genes and environment.

What is genetic determinism?

The incorrect idea that genes completely determine an individual's outcome.

Do genes determine whether someone will develop addiction?

No. Genes influence risk, but they do not solely determine or cause addiction.

Is there a single 'addiction gene'?

No.

Why is addiction considered a polygenic disorder?

Variations in many different genes contribute to addiction rather than disruption of one single gene.

What factors contribute to addiction according to genetic research?

Variations across multiple genes combined with environmental influences.

What do genes do to a person's likelihood of addiction?

Increase or decrease susceptibility/risk rather than determining the outcome.

What is an MZ twin?

A monozygotic/identical twin who shares essentially 100% of segregating genetic variation with their co-twin.

What is a DZ twin?

A dizygotic/fraternal twin who shares, on average, about 50% of segregating genetic variation with their co-twin.

How are MZ and DZ twin correlations used in behavior genetics?

Researchers compare them to estimate genetic, shared environmental, and nonshared environmental influences on variation in a trait.

If MZ twins are substantially more similar on a trait than DZ twins, what does that suggest?

Genetic influences contribute to variation in that trait.

In the Chapter 2 twin-study example, what were the MZ and DZ correlations?

MZ = .80 and DZ = .45.

How is nonshared environmental influence estimated in the twin example?

1.00 − rMZ.

How is genetic influence estimated in the twin example?

2(rMZ − rDZ).

How is shared environmental influence estimated in the twin example?

rMZ − 2(rMZ − rDZ).

Using rMZ = .80 and rDZ = .45, what was the estimated genetic influence?

.70, or 70%.

Using rMZ = .80, what was the estimated nonshared environmental influence?

.20, or 20%.

Using rMZ = .80 and rDZ = .45, what was the estimated shared environmental influence?

.10, or 10%.

Approximately how heritable is Alcohol Dependence/Alcohol Use Disorder according to the slides?

Approximately 50%.

What does it mean to say AUD is approximately 50% heritable?

About 50% of the variation in AUD liability within the studied population is associated with genetic differences; it does NOT mean an individual's AUD is '50% genetic.'

Is heritability an individual estimate or a population estimate?

A population estimate.

Why can't a heritability estimate automatically be applied to an individual?

It describes variation within the population from which it was estimated, not how much of one person's condition is caused by genes.

Can heritability estimates vary?

Yes. They can vary across populations, demographics, environments, and time.

Do basic heritability estimates account for gene-environment interactions?

No.

What did the multivariate twin study suggest about genetic influences across different SUDs?

A substantial proportion of genetic influences are shared across different substance use disorders, but substance-specific genetic influences also exist.

What does molecular genetics focus on?

Identifying specific genetic variations and determining whether they are related to behavioral phenotypes.

Approximately how much human DNA is shared between people?

About 99.8-99.9%.

Why can a tiny percentage of DNA difference still matter?

Even 0.1% of roughly 3 billion DNA bases represents about 3 million differences.

What genetic variations have been a major focus of molecular genetic studies?

Single nucleotide polymorphisms, or SNPs.

What is a SNP?

A single nucleotide polymorphism, a variation at a single position in DNA.

How are inherited polymorphisms represented in the slides?

Genotypes such as AA, Aa, and aa.

What is an allele?

A version of a genetic variant inherited from a parent.

How many copies of a particular 'high-risk' allele could someone inherit?

0, 1, or 2.

What do molecular genetic studies test?

Whether a particular genetic region or variant is associated with a behavioral phenotype.

What two molecular genetic approaches are listed?

Linkage analysis and association analysis.

What happens to alcohol during metabolism?

Alcohol → acetaldehyde → acetate.

What enzyme converts alcohol to acetaldehyde?

Alcohol dehydrogenase (ADH).

What enzyme helps convert acetaldehyde to acetate?

Aldehyde dehydrogenase (ALDH).

What does ADH1B*2 do?

Converts alcohol to acetaldehyde faster.

What does ADH1C*1 do?

Converts alcohol to acetaldehyde faster.

What does ALDH2*2 do?

Slows the breakdown of acetaldehyde.

What genetic variants were described as having protective effects against alcoholism?

ADH1B*2, ADH1C*1, and ALDH2*2.

Why can some alcohol-metabolism variants be protective?

They alter alcohol metabolism in ways that can increase unpleasant effects, making heavy alcohol consumption less reinforcing.

What is the flushing response?

Dysphoric/unpleasant effects that can occur shortly after drinking, including facial reddening, heart palpitations, nausea, and dizziness.

How quickly can the flushing response occur?

Within about 15 minutes of drinking.

Are ethnic-group differences in flushing described as cultural or metabolic in the slides?

Metabolic.

What was the early hope of molecular genetics research?

Researchers hoped to identify a manageable number of genes that each explained meaningful portions of the variation in complex traits.

What is the 'grim reality' of molecular genetics for psychiatric traits?

Psychiatric traits are highly polygenic and influenced by hundreds of genes, with individual variants usually having extremely small effects.

How much variation does an individual genetic variant typically explain according to the slides?

Less than 0.5%.

How much trait variation do associated variants typically explain in total according to the slides?

Usually less than 8%, far less than heritability estimates from twin studies.

What is a GWAS?

Genome-Wide Association Study/Analysis, which tests genetic variants across the genome for associations with a trait or disorder.

Why does GWAS require a very strict significance threshold?

Millions of SNPs are tested, creating a large multiple-testing problem.

What is the genome-wide significance threshold listed in the slides?

p < 5 × 10^-8.

What happened as alcohol GWAS sample sizes became much larger?

Researchers detected more statistically significant genetic associations.

Which alcohol-metabolism gene was highlighted in the 2018 Alcohol Dependence GWAS?

ADH1B.

Why should researchers care about genetic variants with very small effect sizes?

A variant can point toward a biologically important pathway or treatment target even if the variant itself explains very little population variation.

What DRD2 example illustrates why small genetic effects can still matter?

DRD2 variants explain only about 0.2% of variation in schizophrenia, yet antipsychotic drugs targeting the DRD2 receptor produce clinically significant symptom reductions in about 40% of patients.

What is a gene-environment interaction?

A situation in which genetic influences and environmental experiences work together so that the effect of one depends on the other.

What are examples of genetic contributions relevant to addiction?

Tolerance, neurotransmitter processes, brain development, and other biological characteristics.

What are examples of environmental contributions relevant to addiction?

Home environment, inadequate monitoring/supervision, marital discord, childhood trauma, and other experiences.

What is gene-environment correlation (rGE)?

The idea that genetic influences can contribute to the environments people experience or create.

What are the three types of gene-environment correlation?

Passive, active, and evocative.