What is the primary difference between Monozygotic (MZ) and Dizygotic (DZ) twins in biological research?

MZ twins share 100% of their genetic material, while DZ twins share approximately 50%. By comparing these groups, researchers can determine if a behavior is more likely inherited (higher concordance in MZ) or environmentally driven.

How does the Biological Theory of addiction differ from Social Learning Theory?

The Biological Theory focuses on 'nature' (genetics and brain chemistry), whereas Social Learning Theory focuses on 'nurture' (observing and imitating role models in the environment).

What is the distinction between 'Tolerance' and 'Withdrawal' in a biological context?

Tolerance is the brain's adaptation to a substance requiring higher doses for the same effect, while withdrawal is the physical and psychological distress experienced when the substance is removed.

Why is it a mistake to say there is a single 'addiction gene'?

Addiction is a complex, polygenic trait involving many different genes that affect various systems like reward processing and impulse control, rather than being controlled by one specific gene.

What is the danger of using a purely biological explanation for addiction?

It can be reductionist, meaning it oversimplifies a complex human behavior by ignoring critical environmental factors like peer pressure, trauma, and socioeconomic status.

Does a high concordance rate in MZ twins prove that addiction is 100% genetic?

No, because MZ twins also usually share the same environment. Unless the concordance rate is 100%, environmental factors must also play a role in the development of the addiction.

Define 'Genetic Vulnerability' in the context of addiction.

It is an inherited susceptibility that increases the risk of developing an addiction, though it requires environmental triggers to manifest as a disorder.

What are 'Concordance Rates'?

A measure used in twin studies to express the probability that one twin will possess a trait or disorder if the other twin already has it.

What is the 'Diathesis-Stress Model'?

A psychological theory that explains a disorder as the result of an interaction between a pre-existing biological vulnerability (diathesis) and external stressful life events.

How do genes influence the likelihood of addiction?

Genes can influence how neurotransmitters like dopamine are processed in the brain's reward system, affecting how much pleasure a person feels from a substance or how quickly they develop tolerance.

The Biological Theory of Addiction | AQA GCSE Psychology

Psychological Problems

The Biological Theory of Addiction

Summary

The biological theory of addiction posits that substance use disorders are primarily driven by physiological factors, including genetic predispositions and neurochemical adaptations. It emphasizes the 'nature' side of the nature-nurture debate, suggesting that an individual's biological makeup significantly influences their vulnerability to developing addictive behaviors.

1. Definition & Core Concepts

Biological Theory: This perspective argues that addiction is a physical disease or a result of inherited traits rather than a choice or a purely learned behavior.
Nature vs. Nurture: In the context of addiction, the biological theory aligns with the nature argument, suggesting that internal biological structures and processes dictate behavioral outcomes.
Genetic Vulnerability: This refers to an inherited susceptibility to addiction, where certain genetic markers make an individual more likely to struggle with substance control if exposed to the substance.

2. Underlying Principles: The Diathesis-Stress Model

Polygenic Inheritance: Addiction is rarely linked to a single 'addiction gene'; instead, it is thought to be polygenic, involving multiple genes that influence how the brain processes rewards and manages stress.
Diathesis-Stress Model: This framework explains that a biological 'diathesis' (predisposition) remains dormant until triggered by environmental 'stress' (such as trauma or peer pressure).
Neuroadaptation: The brain physically changes in response to chronic substance use, leading to tolerance (the need for higher doses) and withdrawal (physical distress when the substance is absent).

Diagram of the Diathesis-Stress Model showing how genetic predisposition and environmental triggers combine to result in addictive behavior.

3. Methods & Techniques: Twin Studies

Monozygotic (MZ) vs. Dizygotic (DZ): Researchers compare identical twins (MZ), who share 100% of their DNA, with fraternal twins (DZ), who share approximately 50%, to isolate genetic influence.
Concordance Rates: This is the probability that if one twin has an addiction, the other will also have it; significantly higher rates in MZ twins compared to DZ twins suggest a strong genetic component.
Control for Environment: Because twins usually grow up in the same household, researchers assume the environment is constant, allowing differences in concordance to be attributed to genetics.

4. Key Distinctions

5. Exam Strategy & Tips