Home / Courses / Abnormal Psychology / Unit 2

Abnormal Psychology Unit 2: Models of Psychopathology

Each model of psychopathology offers a different answer to the question of why disorders develop and how to treat them. Modern clinicians combine them in integrative frameworks such as the diathesis-stress and biopsychosocial models.

Covers: The biological model: brain, neurotransmitters and genes, Twin, family and adoption studies, The psychodynamic model, The behavioral model, The cognitive model, Humanistic and existential models, Sociocultural and family-systems models, Diathesis-stress, biopsychosocial and developmental views

Study guide

The biological model views abnormal behavior as the result of physical processes in the brain and body. Neurons communicate across synapses using neurotransmitters such as serotonin, dopamine, norepinephrine, GABA and glutamate; unusual activity in these systems is linked to many disorders. Brain structures matter too, such as the amygdala in fear, the prefrontal cortex in planning and impulse control, and the hippocampus in memory and stress regulation. The endocrine system, especially the hypothalamic-pituitary-adrenal (HPA) axis that releases cortisol, connects stress to the body. Genes do not cause disorders directly; most disorders are polygenic, meaning many genes of small effect each add a little risk. Researchers use family, twin and adoption studies to separate genetic from environmental influence.

Twin studies compare identical (monozygotic, MZ) twins, who share about 100% of their genes, with fraternal (dizygotic, DZ) twins, who share about 50%. If MZ twins show higher concordance, meaning both twins have the disorder, than DZ twins, genes likely contribute. A rough estimate of heritability is Falconer's formula, h² = 2(rMZ − rDZ). Heritability describes how much of the variation in a trait across a population is due to genetic differences; it does not say how much of one person's disorder is genetic. Adoption studies compare adopted children with biological and adoptive relatives. Epigenetics adds that environments can change whether genes are expressed without altering the DNA sequence. The biological model leads to treatments such as medication, brain stimulation and, rarely, psychosurgery.

The psychodynamic model, founded by Sigmund Freud, holds that behavior is driven by unconscious conflicts among the id (instinctual drives), ego (reality-based problem solving) and superego (internalized moral standards), often rooted in childhood. Ego defense mechanisms such as repression, projection, displacement and denial reduce anxiety but can become maladaptive. Later psychodynamic thinkers emphasized relationships: object relations theorists and attachment research focus on early bonds with caregivers. The behavioral model explains abnormal behavior as learned. In classical conditioning, a neutral stimulus paired with an aversive one comes to trigger fear, as in John Watson's Little Albert study. In operant conditioning, behavior is shaped by reinforcement and punishment; avoidance can be negatively reinforced because it removes anxiety. Modeling, studied by Albert Bandura, shows that people also learn by watching others.

The cognitive model focuses on how people think. Aaron Beck described automatic thoughts and cognitive distortions, such as overgeneralization and catastrophizing, and a negative cognitive triad about the self, world and future in depression. Albert Ellis argued that irrational beliefs, such as 'I must be loved by everyone,' produce emotional disturbance, summarized by his ABC model: activating event, belief, consequence. The humanistic model of Carl Rogers proposes that people naturally strive toward self-actualization, but conditions of worth imposed by others can block growth; client-centered therapy offers unconditional positive regard, empathy and genuineness. The existential model emphasizes freedom, responsibility and the search for meaning, holding that anxiety follows from avoiding these. The sociocultural model looks at social roles, labels, poverty, discrimination, culture and family systems, where one member's symptoms may reflect patterns in the whole family.

No single model explains any disorder well, so modern clinicians integrate them. The diathesis-stress model holds that a predisposition (diathesis), which can be genetic, biological or psychological, interacts with stressful life events to produce a disorder; neither alone is usually enough. The biopsychosocial model holds that biological, psychological and social factors interact and influence one another, for example when chronic stress alters brain chemistry, which then changes thinking and relationships. Developmental psychopathology adds two useful ideas. Equifinality means different pathways can lead to the same disorder, and multifinality means the same risk factor can lead to different outcomes. Protective factors and resilience explain why many people exposed to risk never develop a disorder. On exams, expect to match therapies, terms and theorists to the correct model.

Key ideas

• The biological model locates causes in neurotransmitters, brain structures, hormones and genes, and favors medical treatments.
• Higher concordance in identical than fraternal twins suggests a genetic contribution, but never proves genes alone cause a disorder.
• Heritability describes the share of variation in a population due to genetic differences, not a single person's genetic fraction.
• Psychodynamic theory explains symptoms as results of unconscious conflicts and defense mechanisms shaped in childhood.
• Behavioral theory explains disorders through classical conditioning, operant conditioning and modeling.
• Cognitive theory says that maladaptive thoughts and beliefs, not events themselves, drive emotional problems.
• Diathesis-stress and biopsychosocial models integrate vulnerability and stress across levels of analysis.

Formulas and rules

Common mistakes

• Saying a heritability of 0.60 means 60% of a person's disorder is caused by genes.
• Treating MZ concordance below 100% as proof that genes play no role; it shows that environment also matters.
• Mixing up negative reinforcement (removing something unpleasant to increase a behavior) with punishment.
• Attributing the ABC model to Beck or the cognitive triad to Ellis.
• Confusing equifinality with multifinality.

Before the test, make sure you can

• Explain how neurotransmitters, brain structures and the HPA axis are linked to disorders.
• Calculate concordance and a Falconer heritability estimate, and interpret them correctly.
• Describe the id, ego, superego and at least four defense mechanisms.
• Apply classical conditioning, operant conditioning and modeling to explain how a fear or habit is learned and maintained.
• Compare Beck's and Ellis's cognitive theories.
• Describe the humanistic and existential models and their therapies.
• Explain sociocultural factors, including labeling, poverty, discrimination and family systems.
• Use the diathesis-stress and biopsychosocial models to explain a case.

Words to know

Neurotransmitter

A chemical that carries signals across a synapse from one neuron to another, such as serotonin, dopamine or GABA.

HPA axis

The hypothalamic-pituitary-adrenal stress system that releases cortisol in response to stress.

Polygenic

Influenced by many genes, each of which adds a small amount of risk.

Concordance

The degree to which both members of a twin pair or family pair share a disorder.

Heritability

The proportion of variation in a trait within a population that is due to genetic differences.

Epigenetics

Changes in gene expression caused by environmental factors without changes to the DNA sequence.

Defense mechanism

In psychodynamic theory, an unconscious ego strategy, such as repression or projection, that reduces anxiety.

Classical conditioning

Learning in which a neutral stimulus becomes associated with a stimulus that naturally triggers a response.

Negative reinforcement

Increasing a behavior by removing an unpleasant state when the behavior occurs.

Modeling

Learning by observing and imitating others, studied by Albert Bandura.

Automatic thoughts

Quick, often unnoticed thoughts that arise in situations and shape emotional reactions, central to Beck's theory.

Irrational beliefs

Ellis's term for rigid, absolute demands (musts and shoulds) that lead to emotional disturbance.

Conditions of worth

In Rogers' theory, standards a person must meet to receive positive regard from others.

Unconditional positive regard

Full acceptance of a client regardless of what they say or do, a core condition of client-centered therapy.

Family systems theory

The view that a family is a system whose structure and communication patterns can maintain a member's symptoms.

Diathesis-stress model

The view that a disorder develops when a predisposition interacts with a sufficiently stressful environment.

Biopsychosocial model

An integrative view that biological, psychological and social factors interact to produce and maintain disorders.

Equifinality

The principle that different developmental pathways can lead to the same disorder.

Multifinality

The principle that the same risk factor can lead to different outcomes in different people.

Sample practice questions

30 more questions like these, from level 1 to 5, are in the practice set.