Biological Explanations for Schizophrenia

Biological Explanations: Genetics & Family Studies

Biological explanations have received the most research support to date (Comer, 2013). In particular, the role of genetics and neural correlates such as dopamine.

‘Diathesis-stress’ relationship

The importance of biological explanations for schizophrenia does not deny the importance of psychological factors that play in the onset of this disorder.
Current thinking is that a ‘diathesis-stress’ relationship may be at work, with a biological predisposition for schizophrenia only developing into the disorder if other significant psychological stressors are present in a person’s life.

Genetic factors

One possible explanation of schizophrenia may be heredity i.e. genetics.
Schizophrenia tends to run in families, but only among individuals who are genetically related rather than related by marriage. The risk of developing the disorder among individuals who have family members with schizophrenia is higher than it is for those who do not.

Combination of genes

No one gene is thought to be responsible for this disorder – it’s more likely that different combinations of genes make individuals more vulnerable to schizophrenia. Having these genes does not necessarily mean an individual will develop schizophrenia.

Family studies

Family studies (Gottesman and Shields, 1991) find individuals who have schizophrenia and determine whether their biological relatives are similarly affected more often than non-biological relatives.
Family studies have established that schizophrenia is more common among biological relatives of a person with schizophrenia, and that the closer the degree of genetic relatedness, the greater the risk.

Gottesman and Shield

For example, in Gottesman and Shield’s study, children with two schizophrenic parents had a concordance rate of 46%, children with one schizophrenic parent a rate of 13% and siblings (where a brother or sister had schizophrenia) a concordance rate of 9%.

Biological Explanations: Twin & Adoption Studies

Biological explanations have received the most research support to date (Comer, 2013), in particular the role of genetics and neural correlates such as dopamine.

Twin studies

If monozygotic (MZ – genetically identical) twins are more concordant than dizygotic (DZ – who share only 50% of their genes), then this suggests that the greater similarity is due to genetic factors.
Joseph (2004) calculated that the pooled data for all schizophrenia twin studies carried out prior to 2001 showed a concordance rate for MZ twins of 40.4% and 7.4% for DZ twins.

Lower concordance rate for MZ twins

More recently, methodologically sound studies (e.g. those using ‘blind’ diagnoses where the researchers assessing do not know whether the twins are MZ or DZ) have tended to report a lower concordance rate for MZ twins than earlier studies.
Despite this, however, such studies still support the genetic position because they show a concordance rate for MZ twins that is many times higher than for DZ twins.

Adoption studies

Because of the difficulties of disentangling genetic and environmental influences for individuals who share genes and environment, studies of genetically related individuals who have been reared apart are used.

Tienari et al (2000)

Probably the most methodologically sound study of this type was carried out by Tienari et al (2000) in Finland.
Of the 164 adoptees whose biological mothers had been diagnosed with schizophrenia, 11 (6.7%) also received a diagnosis of schizophrenia, compared to just 4 (2%) of the 197 controls adoptees (those born to non-schizophrenic mothers). The investigators concluded that these findings showed that the genetic liability to schizophrenia had been ‘decisively confirmed.’

Evaluation of biological explanations

Strengths
- There is overwhelming evidence to suggest that genetic factors make some people much more vulnerable to developing the disorder than others.
Limitations
- Could be explained by common family backgrounds and experiences rather than genetics (nature/nurture).
- MZ twins treated more similarly than DZ twins.
- Adoptees may be selectively placed with families.

1Social Influence

2Memory

3Attachment

3.1Attachment

3.1.1(2026 Exams) Caregiver-Infant Interaction

3.1.2(2026 Exams) Condon & Sander (1974)

3.1.3(2026 Exams) Schaffer & Emerson (1964)

3.1.4(2026 Exams) Multiple Attachments

3.1.5(2026 Exams) Studies on the Role of the Father

3.1.6(2027 Exams) The Concept of Attachment

3.1.7Animal Studies of Attachment

3.1.8Explanations of Attachment

3.1.9Attachment Types - Strange Situation

3.1.10Cultural Differences in Attachment

3.1.11Disruption of Attachment

3.1.12Disruption of Attachment - Privation

3.1.13Overcoming the Effects of Disruption

3.1.14(2026 Exam) The Effects of Institutionalisation

3.1.15(2027 Exam) The Effects of Institutionalisation

3.1.16Early Attachment

3.1.17Critical Period of Attachment

3.1.18(2026 Exam) End of Topic Test - Attachment

3.1.19(2027 Exam) End of Topic Test - Attachment

3.1.20(2026 Exams) Exam-Style Question - Attachment

3.1.21(2027 Exams) Exam-Style Question - Attachment

3.1.22Top Grade AO2/AO3 - Attachment

4(2026 Exams) Psychopathology

4.1Psychopathology

4.1.1Abnormality

4.1.2Abnormality 2

4.1.3Phobias, Depression & OCD

4.1.4Phobias: Behavioural Approach

4.1.5Evaluation of Behavioural Explanations of Phobias

4.1.6Depression: Cognitive Approach

4.1.7OCD: Biological Approach

4.1.8Evidence for the Biological Approach

4.1.9End of Topic Test - Psychopathy

4.1.10Exam-Style Question - Phobias

4.1.11Top Grade AO2/AO3 - Psychopathology

4.1.12Diagnostic Misconceptions - Phobia vs Fear

4.1.13Diagnostic Misconceptions - Depression & Self-Harm

4.1.14Diagnostic Misconceptions - Desensitisation

5(2027 Exams) Clinical Psychology & Mental Health

5.1Clinical Psychology & Mental Health

5.1.1Deviation from Social Norms

5.1.2Deviation from Social Norms 2

5.1.3Phobias, Depression & OCD

5.1.4Phobias: Behavioural Approach

5.1.5Evaluation of Behavioural Explanations of Phobias

5.1.6Depression: Cognitive Approach

5.1.7OCD: Biological Approach

5.1.8Evidence for the Biological Approach

5.1.9End of Topic Test - Psychopathy

5.1.10Exam-Style Question - Phobias

5.1.11Top Grade AO2/AO3 - Psychopathology

5.1.12Diagnostic Misconceptions - Phobia vs Fear

5.1.13Diagnostic Misconceptions - Depression & Self-Harm

5.1.14Diagnostic Misconceptions - Desensitisation

6Approaches in Psychology

6.1Approaches in Psychology

6.1.1(2026 Exams) Psychology as a Science

6.1.2(2026 Exams) Origins of Psychology

6.1.3(2026 Exams) Problems with Introspection

6.1.4The Behaviourist Approach - Classical Conditioning

6.1.5Pavlov's Experiment

6.1.6Little Albert Study

6.1.7The Behaviourist Approach - Operant Conditioning

6.1.8(2026 Exams) Social Learning Theory

6.1.9(2026 Exam) The Cognitive Approach 1

6.1.10(2026 Exams)The Cognitive Approach 2

6.1.11(2026 Exams) The Biological Approach

6.1.12(2027 Exams) Social Learning Theory

6.1.13(2027 Exams) The Cognitive Approach 1

6.1.14(2027 Exams)The Cognitive Approach 2

6.1.15(2027 Exams) The Biological Approach

6.1.16(2027 Exam) The Biological Approach 2

6.1.17Gottesman (1991) - Twin Studies

6.1.18Brain Scanning

6.1.19Structure of Personality & Little Hans

6.1.20The Psychodynamic Approach (A2 only)

6.1.21(2026 Exams) Humanistic Psychology (A2 only)

6.1.22(2027 Exams) Humanistic Psychology (A2 only)

6.1.23Aronoff (1957) (A2 Only)

6.1.24(2026 Exam) Rogers' Client-Centred Therapy A2 only

6.1.25(2026 Exam) Exam-Style Question - Approaches

6.1.26(2026 Exam) End of Topic Test - Approaches

6.1.27(2027 Exam) End of Topic Test - Approaches

6.2Comparison of Approaches (A2 only)

6.2.1Psychodynamic Approach

6.2.2Cognitive Approach

6.2.3Biological Approach

6.2.4Behavioural Approach

6.2.5End of Topic Test - Comparison of Approaches

7Biopsychology

7.1Biopsychology

7.1.1Nervous System Divisions

7.1.2Neuron Structure & Function

7.1.3Neurotransmitters

7.1.4Endocrine System Function

7.1.5Fight or Flight Response

7.1.6The Brain (A2 only)

7.1.7Localisation of Brain Function (A2 only)

7.1.8(2026 Exam) Studying the Brain (A2 only)

7.1.9(2026 Exam) CIMT (A2 Only) & Postmortem

7.1.10(2027 Exam) Studying the Brain (A2 only)

7.1.11(2027 Exam) CIMT (A2 Only) & Postmortem

7.1.12(2026 Exams) Biological Rhythms (A2 only)

7.1.13(2026 Exams) Studies on Biological Rhythms (A2)

7.1.14Top Grade AO2/AO3 - Biopsychology

7.1.15Diagnostic Misconceptions - Plasticity & Recovery

7.1.16Diagnostic Misconceptions - Endogenous Pacemakers

7.1.17(2026 Exams) End of Topic Test - Biopsychology

7.1.18(2027 Exams) End of Topic Test - Biopsychology

8Research Methods

8.1Research Methods

8.1.1Experimental Method

8.1.2Observational Techniques

8.1.3Covert, Overt & Controlled Observation

8.1.4Self-Report Techniques

8.1.5Correlations

8.1.6Exam-Style Question - Research Methods

8.1.7Diagnostic Misconceptions - Sign Test

8.1.8Diagnostic Misconceptions - Content & Thematic

8.1.9Diagnostic Misconceptions - Valid vs Reliable

8.1.10Diagnostic Misconceptions - Confounding Variable

8.1.11End of Topic Test - Research Methods

8.2Scientific Processes

8.3Data Handling & Analysis

8.3.1Types of Data

8.3.2Descriptive Statistics

8.3.3Correlation

8.3.4Evaluation of Descriptive Statistics

8.3.5Presentation & Display of Data

8.3.6Levels of Measurement (A2 only)

8.3.7(2026 Exams) Content Analysis (A2 only)

8.3.8(2027 Exams) Coding in Content Analysis (A2 only)

8.3.9Case Studies (A2 only)

8.3.10(2026 Exams) Thematic Analysis (A2 only)

8.3.11(2026 Exams) End of Topic Test - Data Handling

8.3.12(2027 Exams) End of Topic Test - Data Handling

8.4Inferential Testing

8.4.1Introduction to Inferential Testing

8.4.2Sign Test

8.4.3Piaget Conservation Experiment

8.4.4Non-Parametric Tests

9Issues & Debates in Psychology (A2 only)

9.1Issues & Debates in Psychology (A2 only)

9.1.1Culture Bias

9.1.2Sub-Culture Bias

9.1.3Gender Bias

9.1.4Ethnocentrism

9.1.5Cross Cultural Research

9.1.6Free Will & Determinism

9.1.7Comparison of Free Will & Determinism

9.1.8Reductionism & Holism

9.1.9Reductionist & Holistic Approaches

9.1.10Nature-Nurture Debate

9.1.11Interactionist Approach

9.1.12Nature-Nurture Methods

9.1.13Nature-Nurture Approaches

9.1.14Idiographic & Nomothetic Approaches

9.1.15Socially Sensitive Research

9.1.16End of Topic Test - Issues and Debates

10Option 1: Relationships (A2 only)

10.1Relationships: Sexual Relationships (A2 only)

10.1.1(2026 Exams) Sexual Selection

10.1.2(2026 Exams) Intersexual & Intrasexual

10.1.3(2026 Exams) Evaluation of Sexual Selection

10.1.4Factors Affecting Attraction: Self-Disclosure

10.1.5Evaluation of Self-Disclosure Theory

10.1.6Factors Affecting Attraction: Physical Attributes

10.1.7Matching Hypothesis Studies

10.1.8Factors Affecting Physical Attraction

10.1.9Factors Affecting Attraction: Filter Theory 1

10.1.10Factors Affecting Attraction: Filter Theory 2

10.1.11Evaluation of Filter Theory

10.1.12(2026 Exams) End of Topic Test - Relationships

10.1.13(2027 Exams) End of Topic Test - Relationships

10.2Relationships: Romantic Relationships (A2 only)

10.2.1Social Exchange Theory

10.2.2Evaluation of Social Exchange Theory

10.2.3Equity Theory

10.2.4Evaluation of Equity Theory

10.2.5Rusbult’s Investment Model

10.2.6Evaluation of Rusbult's Investment Model

10.2.7Relationship Breakdown

10.2.8Studies on Relationship Breakdown

10.2.9Evaluation of Relationship Breakdown

10.2.10End of Topic Test - Romantic relationships

10.3(2026 Exams) Relationships: Virtual (A2 only)

10.3.1Virtual Relationships in Social Media

10.3.2Evaluation of Reduced Cues & Hyperpersonal

10.3.3Self Disclosure in Computer Communication

10.3.4Parasocial Relationships

10.3.5Attachment Theory & Parasocial Relationships

10.3.6Evaluation of Parasocial Relationship Theories

10.3.7End of Topic Test - Virtual & Parasocial Realtions

10.4(2027 Exams) Relationships: Online (A2 only)

10.4.1Online Relationships

10.4.2Evaluation of Reduced Cues & Hyperpersonal

10.4.3Self Disclosure in Online Relationships

10.4.4Parasocial Relationships

10.4.5Attachment Theory & Parasocial Relationships

10.4.6Evaluation of Parasocial Relationship Theories

10.4.7End of Topic Test - Online Relationships

11Option 1: Gender (A2 only)

11.1(2026 Exams) Gender (A2 only)

11.1.1Sex, Gender & Androgyny

11.1.2Gender Identity Disorder

11.1.3Biological & Social Explanations of GID

11.1.4Biological Influences on Gender

11.1.5Effects of Hormones on Gender

11.1.6Kohlberg’s Theory of Gender Constancy

11.1.7Evaluation of Kohlberg's Theory

11.1.8Gender Schema Theory

11.1.9Psychodynamic Approach to Gender Development 1

11.1.10Psychodynamic Approach to Gender Development 2

11.1.11Social Approach to Gender Development

11.1.12Criticisms of Social Theory

11.1.13Media Influence on Gender Development

11.1.14Cross Cultural Research

11.1.15Childcare & Gender Roles

11.1.16End of Topic Test - Gender 1

11.1.17End of Topic Test - Gender 2

11.1.18End of Topic Test - Gender 3

11.2(2027 Exams) Gender (A2 only)

11.2.1Biological Sex

11.2.2The Role of Hormones in Biological Sex

11.2.3Biological Explanations of Gender Development

11.2.4Gender Identities & BSRI

11.2.5Kohlberg’s Theory of Gender Constancy

11.2.6Evaluation of Kohlberg's Theory

11.2.7Gender Schema Theory

11.2.8Social Approach to Gender Development

11.2.9Criticisms of Social Theory

11.2.10Media Influence on Gender Development

11.2.11Gender Incongruence

11.2.12End of Topic Test - Gender

12Option 1: Cognition & Development (A2 only)

12.1Cognition & Development (A2 only)

12.1.1Piaget’s Theory of Cognitive Development 1

12.1.2Piaget's Theory of Cognitive Development 2

12.1.3Schema Accommodation Assimilation & Equilibration

12.1.4Piaget & Inhelder’s Three Mountains Task (1956)

12.1.5Conservation & Class Inclusion

12.1.6Evaluation of Piaget

12.1.7Vygotsky

12.1.8Evaluation of Vygotsky

12.1.9Baillargeon

12.1.10Baillargeon's studies

12.1.11Evaluation of Baillargeon

12.1.12(2026 Exams) Sense of Self & Theory of Mind

12.1.13(2027 Exams) Sense of Self & Theory of Mind

12.1.14(2026 Exams) Baron-Cohen Studies

12.1.15(2027 Exams) Baron-Cohen Studies

12.1.16Selman’s Five Levels of Perspective Taking

12.1.17Biological Basis of Social Cognition

12.1.18Evaluation of Biological Basis of Social Cognition

12.1.19(2026 Exams) Issues in Social Neuroscience

12.1.20(2027 Exams) Issues in Social Neuroscience

12.1.21Top Grade AO2/AO3 - Cognition & Development

12.1.22End of Topic Test - Cognition & Development 1

12.1.23End of Topic Test - Cognition & Development 2

12.1.24(2026 Exams) End of Topic Test - Cognition 3

12.1.25(2027 Exams) End of Topic Test - Cognition 3

13Option 2: Schizophrenia (A2 only)

13.1Schizophrenia: Diagnosis (A2 only)

13.1.1(2026 Exam) Classification & Diagnosis

13.1.2(2026 Exam) Symptoms of Schizophrenia

13.1.3(2026 Exams) Reliability & Validity of Diagnosis

13.1.4(2027 Exam) Symptoms of Schizophrenia

13.1.5(2026 Exams) Gender & Cultural Bias

13.1.6(2027 Exams) Issues in Diagnosis

13.1.7Pinto (2017) & Copeland (1971)

13.1.8(2026 Exams) End of Topic Test - Schizophrenia

13.1.9(2027 Exams) End of Topic Test - Schizophrenia

13.2Schizophrenia: Treatment (A2 only)

13.2.1Family-Based Psychological Explanations

13.2.2Evaluation of Family-Based Explanations

13.2.3Cognitive Explanations

13.2.4Drug Therapies

13.2.5Evaluation of Drug Therapies

13.2.6Biological Explanations for Schizophrenia

13.2.7Dopamine Hypothesis

13.2.8(2026 Exams) Psychological Therapies 1

13.2.9(2027 Exams) Psychological Therapies 1

13.2.10(2026 Exams) Psychological Therapies 2

13.2.11(2027 Exams) Psychological Therapies 2

13.2.12Interactionist Approach - Diathesis-Stress Model

13.2.13Interactionist Approach - Triggers & Treatment

13.2.14Evaluation of the Interactionist Approach

13.2.15(2026 Exams) Evaluation of Psychological Therapies

13.2.16(2027 Exams) Evaluation of Psychological Therapies

13.2.17Diagnostic Misconceptions - CBT & CBTp

13.2.18End of Topic Test - Treatments 1

13.2.19(2026 Exams) End of Topic Test - Treatments 2

13.2.20(2027 Exams) End of Topic Test - Treatments 2

14Option 2: Eating Behaviour (A2 only)

14.1Eating Behaviour (A2 only)

14.1.1Explanations for Food Preferences

14.1.2Birch et al (1987) & Lowe et al (2004)

14.1.3Control of Eating Behaviours

14.1.4Control of Eating Behaviour: Leptin

14.1.5Biological Explanations for Anorexia Nervosa

14.1.6Psychological Explanations: Family Systems Theory

14.1.7Psychological Explanations: Social Learning Theory

14.1.8Psychological Explanations: Cognitive Theory

14.1.9Biological Explanations for Obesity

14.1.10Biological Explanations: Studies

14.1.11(2026 Exams) Psychological Explanations

14.1.12(2027 Exams) Psychological Explanations

14.1.13(2026 Exams) Psychological Explanations: Studies

14.1.14(2027 Exams) Psychological Explanations: Studies

14.1.15End of Topic Test - Eating Behaviour

15Option 2: Stress (A2 only)

15.1Stress (A2 only)

15.1.1Physiology of Stress

15.1.2Role of Stress in Illness

15.1.3Role of Stress in Illness: Studies

15.1.4Social Readjustment Rating Scales

15.1.5Hassles & Uplifts Scales

15.1.6Stress, Workload & Control

15.1.7Stress Level Studies

15.1.8Physiological Measures of Stress

15.1.9Individual Differences

15.1.10Stress & Gender

15.1.11(2026 Exams) Drug Therapy & Biofeedback for Stress

15.1.12(2027 Exams) Drug Therapy & Biofeedback for Stress

15.1.13Stress Inoculation Therapy

15.1.14Social Support & Stress

15.1.15End of Topic Test - Stress 1

15.1.16(2026 Exams) End of Topic Test - Stress 2

15.1.17(2027 Exams) End of Topic Test - Stress 2

16Option 3: Aggression (A2 only)

16.1Aggression: Physiological (A2 only)

16.1.1Neural Mechanisms

16.1.2Serotonin

16.1.3Hormonal Mechanisms

16.1.4Genetic Factors

16.1.5Genetic Factors 2

16.1.6Ethological Explanation

16.1.7Innate Releasing Mechanisms & Fixed Action Pattern

16.1.8Evolutionary Explanations

16.1.9Buss et al (1992) - Sex Differences in Jealousy

16.1.10Evaluation of Evolutionary Explanations

16.1.11End of Topic Test - Aggression: Physiological 1

16.1.12End of Topic Test - Aggression: Physiological 2

16.2Aggression: Social Psychological (A2 only)

16.2.1Social Psychological Explanation

16.2.2Buss (1963) - Frustration/Aggression

16.2.3Social Psychological Explanation 2

16.2.4Social Learning Theory (SLT) 1

16.2.5Social Learning Theory (SLT) 2

16.2.6Limitations of Social Learning Theory (SLT)

16.2.7Deindividuation

16.2.8Deindividuation 2

16.2.9Deindividuation - Diener et al (1976)

16.2.10End of Topic Test - Aggression: Social Psychology

16.2.11Institutional Aggression: Prisons

16.2.12Evaluation of Dispositional & Situational

16.2.13Influence of Computer Games

16.2.14Influence of Television

16.2.15Evaluation of Studies on Media

16.2.16Desensitisation & Disinhibition

16.2.17Cognitive Priming

16.2.18End of Topic Test - Aggression: Social Psychology

17Option 3: Forensic Psychology (A2 only)

17.1Forensic Psychology (A2 only)

17.1.1Defining Crime

17.1.2Measuring Crime

17.1.3(2026 Exams) Offender Profiling

17.1.4(2027 Exams) Offender Profiling

17.1.5Evaluation of Offender Profiling

17.1.6John Duffy Case Study

17.1.7(2026 Exams) Biological Explanations 1

17.1.8(2027 Exams) Biological Explanations 1

17.1.9Biological Explanations 2

17.1.10(2026 Exams) Evaluation- Biological Explanations

17.1.11(2027 Exams) Evaluation- Biological Explanations

17.1.12Cognitive Explanations

17.1.13Moral Reasoning

17.1.14(2026 Exams) Psychodynamic Explanation 1

17.1.15(2026 Exams) Psychodynamic Explanation 2

17.1.16Differential Association Theory

17.1.17Custodial Sentencing

17.1.18(2026 Exams) Effects of Prison

17.1.19(2027 Exams) Effects of Prison

17.1.20Evaluation of the Effects of Prison

17.1.21(2026 Exams) Recidivism

17.1.22Behavioural Treatments & Therapies

17.1.23Effectiveness of Behavioural Treatments

17.1.24Restorative Justice

17.1.25(2026 Exams) End of Topic Test - Forensic 1

17.1.26(2026 Exams) End of Topic Test - Forensic 2

17.1.27(2027 Exams) End of Topic Test - Forensic 1

17.1.28(2027 Exams) End of Topic Test - Forensic 2

18Option 3: Addiction (A2 only)

18.1Addiction (A2 only)

18.1.1Definition

18.1.2(2026 Exams) Brain Neurochemistry Explanation

18.1.3(2026 Exams) Learning Theory Explanation

18.1.4(2026 Exams) Evaluation of a Learning Theory

18.1.5(2027 Exams) Brain Neurochemistry Explanation

18.1.6(2027 Exams) Learning Theory Explanation

18.1.7(2027 Exams) Evaluation of a Learning Theory

18.1.8Cognitive Bias

18.1.9Griffiths on Cognitive Bias

18.1.10Evaluation of Cognitive Theory (A2 only)

18.1.11Gambling Addiction & Learning Theory

18.1.12(2026 Exams) Social Influences on Addiction 1

18.1.13(2027 Exams) Social Influences on Addiction 1

18.1.14Social Influences on Addiction 2

18.1.15Personal Influences on Addiction

18.1.16Genetic Explanations of Addiction

18.1.17(2026 Exams) End of Topic Test - Addiction 1

18.1.18(2026 Exams) End of Topic Test - Addiction 2

18.1.19(2027 Exams) End of Topic Test - Addiction 1

18.1.20(2027 Exams) End of Topic Test - Addiction 2

18.2Treating Addiction (A2 only)

18.2.1Drug Therapy

18.2.2Behavioural Interventions

18.2.3Cognitive Behavioural Therapy

18.2.4(2026 Exams) Theory of Reasoned Action

18.2.5(2026 Exams) Theory of Planned Behaviour

18.2.6Six Stage Model of Behaviour Change

18.2.7(2026 Exams) End of Topic Test - Treating

18.2.8(2027 Exams) End of Topic Test - Treating

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