IB DP Psychology: Option: Abnormal psychology – Revision Notes

Course note: these notes follow IB DP Psychology for first assessment 2019, whose last examination session is November 2026. The replacement course is first assessed in May 2027.

Abnormal psychology is one of the four IB DP Psychology options, examined on Paper 2 through 22-mark essays. It asks how abnormality is defined and diagnosed, what explains disorders and how well treatments work; most schools study one disorder in depth – usually major depressive disorder, used as the example in these notes – and use the biological, cognitive and sociocultural approaches to explain and treat it.

Related: Abnormal psychology study guide and practice questions.

Syllabus coverage (first assessment 2019)

Topic	Content
Factors influencing diagnosis	Normality versus abnormality; classification systems; the role of clinical biases in diagnosis; validity and reliability of diagnosis
Etiology of abnormal psychology	Explanations for disorders; prevalence rates and disorders
Treatment of disorders	Biological treatment; psychological treatment; the role of culture in treatment; assessing the effectiveness of treatment(s)

Definitions of abnormality

Approach	Idea	Limitation
Statistical infrequency	Behaviour that is rare	Some rare behaviours are desirable
Deviation from social norms	Behaviour that breaks norms	Norms vary across cultures and time
Failure to function adequately	Distress and inability to cope	Judgement is subjective
Deviation from ideal mental health	Absence of features such as self-actualisation (Jahoda, 1958)	Ideals are culture-bound

Classification systems: DSM-5 (American Psychiatric Association, 2013) and ICD-11 (World Health Organization). Major depressive disorder in DSM-5 requires five or more symptoms over at least two weeks, including depressed mood or loss of interest.

Diagnosis: key studies

Study	Finding	Use
Rosenhan (1973)	Eight pseudopatients reporting a single hallucinated voice were admitted to 12 hospitals; most were diagnosed with schizophrenia and discharged “in remission”	Validity of diagnosis; labelling
Cooper et al. (1972)	US psychiatrists diagnosed schizophrenia more often, and UK psychiatrists depression, from the same videotaped interviews	Reliability; cultural bias
Regier et al. (2013)	DSM-5 field trials found low inter-rater reliability for major depressive disorder (kappa about 0.28)	Reliability of modern diagnosis

Clinical biases: confirmation bias, cultural bias, gender bias, and somatisation in some cultures – Kleinman (1982) found many Chinese patients diagnosed with neurasthenia met Western criteria for depression but reported physical symptoms.

Explaining depression

Approach	Explanation	Research
Biological	Genetic vulnerability; gene-environment interaction	Kendler et al. (2006), Swedish twins: heritability about 38%, higher in women; Caspi et al. (2003), Dunedin cohort: carriers of the short 5-HTT allele who experienced stressful life events were more likely to become depressed
Cognitive	Negative schemas and the cognitive triad (self, world, future)	Beck (1967); Alloy et al. (1999) longitudinal study linking negative cognitive style to later depression
Sociocultural	Social vulnerability and stressors	Brown and Harris (1978): women in Camberwell with vulnerability factors (such as lack of an intimate relationship, three or more young children at home) were more likely to become depressed after a severe life event

Prevalence: women are diagnosed with depression roughly twice as often as men in many countries; explanations include biological differences, rumination, social roles and differences in help-seeking or diagnosis.

Treatment and effectiveness

Treatment	Evidence	Evaluation
Antidepressants (SSRIs)	Kirsch et al. (2008): meta-analysis of trial data submitted to the US regulator found small differences from placebo except in severe depression	Publication bias; side effects; relapse after stopping
Cognitive behavioural therapy	Elkin et al. (1989), NIMH collaborative study: CBT, interpersonal therapy and imipramine all reduced symptoms; DeRubeis et al. (2005): CBT as effective as medication for moderate to severe depression	Requires motivation; cost; therapist skill
Culture in treatment	Culturally adapted therapies and matching of therapist and client language or ethnicity can improve engagement	Studies often small; “culture” hard to define

Assessing effectiveness: randomised controlled trials, placebo control, double-blind procedures, relapse rates, meta-analysis; the placebo effect and spontaneous remission complicate interpretation.

Worked example: planning an ERQ

Question: “Evaluate one explanation of one disorder.” (22 marks)

• Focus: the biological explanation of major depressive disorder – genetic vulnerability and gene-environment interaction.
• Knowledge and understanding: define heritability; describe Kendler et al. (2006) and Caspi et al. (2003), with aim, method, findings and conclusion.
• Evaluation: twin studies cannot fully separate genes from shared environment; Caspi’s finding supports a diathesis-stress view rather than genes alone; cohort data are correlational, so cause cannot be inferred; contrast with the cognitive explanation (Beck) as an alternative.
• Conclusion: genes appear to raise vulnerability, but the evidence points to an interaction with life events, not a purely biological cause.

Common mistakes / exam traps

• Discussing “abnormality” in general without a disorder. Questions on etiology and treatment require a named disorder.
• Describing Rosenhan without linking to validity. Explain what the study shows about diagnosis.
• Treating heritability as “genes cause X%”. Heritability describes variation within a population, not a percentage of one person’s disorder.
• One-sided treatment essays. Compare biological and psychological treatments and assess effectiveness.
• Over-generalising cultural findings. Kleinman’s sample was Chinese patients in the 1980s; avoid sweeping claims.

Frequently asked questions

How is this option examined? On Paper 2: three 22-mark ERQs are set on each option, and you answer one from your option (SL) or one from each of two options (HL).

Do I need more than one disorder? The syllabus requires knowledge of disorders for etiology and treatment; most schools teach one in depth and refer to others briefly. Check with your teacher.

What is the difference between reliability and validity of diagnosis? Reliability is whether clinicians agree on the same diagnosis (inter-rater reliability), as tested by Cooper et al. (1972). Validity is whether the diagnosis is accurate, i.e. the person really has the disorder, as questioned by Rosenhan (1973). A diagnosis can be reliable without being valid.

What earns criterion D (critical thinking)? Evaluation of studies and theories – methods, ethics, cultural limits, alternative explanations – linked to the question.

Self-test

1. Name two classification systems. DSM-5 and ICD-11.
2. What did Caspi et al. (2003) find? The short 5-HTT allele increased the risk of depression after stressful life events.
3. What is the cognitive triad? Negative views of the self, the world and the future.
4. What did Kirsch et al. (2008) suggest? Antidepressants differ little from placebo except in severe depression.
5. What does inter-rater reliability measure? Agreement between clinicians diagnosing the same case.