Explain unipolar depression and evaluate Oruč et al. (1997)
Compare biochemical, genetic and cognitive explanations of unipolar depression, and use the original studies carefully when evaluating the syllabus evidence.
Section Paper 4 · Specialist Options: Application and Research Methods
Exam scope and assessment notes
Original StudyForA teaching mapped to Cambridge 2028–2030 Version 1. Cambridge's official Reference List explicitly explains that Oruč et al. (1997) is used here as an illustration of a genetic explanation that applies to both bipolar and unipolar disorders, although the original study only sampled bipolar-I participants. Educational content only: not clinical advice, diagnosis, Cambridge material, an official mark scheme or an awarded grade. Human subject-expert review and full timed-paper grading remain pending.
Before you begin
- This lesson covers 9990 Clinical Psychology topic 1.2.2 for the 2028–2030 Version 1 syllabus. It explains theories for study; it does not assess or diagnose a learner.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which description most accurately reports the Oruč et al. (1997) study?
What you will learn
- Describe biochemical explanations without reducing depression to a proven single chemical imbalance
- Explain genetic vulnerability and evaluate what Oruč et al. (1997) actually studied
- Apply Beck’s negative cognitive triad, schemas and attributional style to an example
- Explain learned helplessness and evaluate Seligman et al. (1988) without claiming that correlation proves a cause
Biochemical explanations are theories about interacting processes
A biochemical explanation proposes that processes involving brain chemistry contribute to depressive experiences. The monoamine hypothesis has proposed a role for neurotransmitters such as serotonin and noradrenaline. Treat this as a family of explanatory models, not a settled claim that every depressed person has a measurable shortage of one chemical.
A medicine's effect on a neurotransmitter system does not by itself prove that the same system caused the condition. Symptoms, biology, learning, relationships and circumstances can interact, and mechanisms may differ between people. In an evaluation, identify the biochemical proposal and the evidence needed to test it instead of writing ‘depression is a chemical imbalance’ as a fact.
A 2022 systematic umbrella review by Moncrieff and colleagues found no consistent evidence that depression is caused by lower serotonin activity or concentration. This is evidence against a simple low-serotonin account; it does not show that biology is irrelevant or settle every biochemical model. It is useful to evaluate the scope and quality of the evidence rather than turn one review into a universal conclusion.
Genetic explanations describe possible vulnerability, not a personal prediction
Genetic explanations propose that inherited differences can contribute to vulnerability. Family resemblance alone cannot separate genes from shared environments, and a genetic association does not show that a variant is necessary or sufficient to cause a disorder. A careful account also considers how genes and experience may interact.
The 2028–2030 Cambridge syllabus names Oruč et al. (1997) in this unipolar-depression section. Cambridge's official Reference List explains why: the study's title is about genes in bipolar disorder, it appears here as an illustration of a genetic explanation, and the genetic explanation applies to both bipolar and unipolar disorders. The original article reports 42 patients with bipolar I and 40 healthy controls tested for variants in the 5-HT2C receptor and serotonin-transporter genes. It was not a study sample of people with unipolar depression.
The authors found no significant association in the full patient sample. After dividing the sample by sex, they reported possible trends among women and suggested a minor increase in susceptibility to bipolar disorder. Cambridge's Reference List says detailed statistical tests and their numbers are not required for this study. The small sample and subgroup analysis make the result tentative; it does not establish that either variant causes unipolar depression or predict an individual's future.
This is a useful source-evaluation point: follow Cambridge's stated purpose for the study, but report what the primary article actually says. Cambridge explicitly treats it as an illustration of a genetic explanation that may apply to both disorders, not as a study of unipolar participants. Do not silently relabel its bipolar-I sample as unipolar cases.
Beck’s cognitive theory links interpretation, schemas and the negative triad
Beck’s cognitive theory proposes that negative schemas and biases in interpreting experience can contribute to depressive thinking. The negative cognitive triad concerns a person's negative view of the self, the world or current experience, and the future. These are theoretical patterns, not a checklist for diagnosing a student.
A schema is an organised expectation that guides attention and interpretation. If a person expects failure, they may notice a setback more readily, discount evidence of success or draw a broad conclusion from one event. In an example, show the event, the interpretation and how that interpretation could influence feeling or behaviour; do not assume that one thought causes a disorder.
Attributional style describes how someone explains events. In the learned-helplessness reformulation, explaining negative events as internal (about oneself), stable (unlikely to change) and global (affecting many areas) can make a setback seem uncontrollable and permanent. These dimensions describe a proposed pattern of explanation, not a fixed trait shared by all people with depression.
Learned helplessness and the Seligman et al. (1988) study
The learned-helplessness account proposes that repeated experience of outcomes that seem uncontrollable can weaken expectations that one's actions will make a difference. The human reformulation adds the person's explanations for those outcomes. It is a psychological theory to evaluate, not a judgement that a person has failed to try hard enough.
Seligman et al. (1988) administered the Attributional Style Questionnaire to 39 people with unipolar depression at the beginning and end of cognitive therapy and at a one-year follow-up. They also assessed 12 people with bipolar disorder during a depressive episode. For the unipolar group, pessimistic explanations of bad events correlated with depression severity at intake (r = .56), treatment end (r = .57) and follow-up (r = .64). Explanatory style and symptoms improved by treatment end and remained improved at follow-up.
Repeated assessment gives a picture of change over time, and the study directly addresses the syllabus's explanatory-style example. However, it does not by itself show that changing attributional style caused symptoms to improve: the variables changed together during therapy, with no randomised comparison in this report that isolates that mechanism. The findings support an association in this treatment sample, not a universal explanation or a diagnosis.
Compare explanations and the syllabus debates
Biochemical and genetic explanations emphasise biological influences; Beck’s and learned-helplessness explanations emphasise interpretation and expectations. Nature versus nurture asks how inherited and experienced influences may combine. Reductionism versus holism asks whether one level of explanation is enough or whether interacting levels are needed.
Determinism versus free will can be discussed carefully: an account that locates influences in biology or learned expectations may reduce blame, but it should not imply that a person's future is fixed. Reliability matters when studies use repeated questionnaires: standardised wording can help comparison, but response interpretation and measurement quality still need evaluation.
For a strong answer, name the explanation, connect it to a mechanism, use the study accurately, then state one strength and one limitation. Keep evidence about bipolar disorder separate from evidence about unipolar depression, even when Cambridge lists a study in the unipolar section.
Sources for this lesson
- Cambridge International AS & A Level Psychology 9990 syllabus, 2028–2030
- Cambridge International 9990 Reference List, 2028–2030 · Oruč study context
- Oruč et al. (1997), original article record and abstract · PubMed
- Seligman et al. (1988), original article PDF · University of Pennsylvania
- Abramson, Seligman and Teasdale (1978), learned helplessness reformulation · PubMed
- Beck’s cognitive theory of depression, publisher sample chapter · Guilford Press
- Moncrieff et al. (2022), systematic umbrella review of the serotonin theory · Molecular Psychiatry
Pause and explain
What can Seligman et al. (1988) support about attributional style and unipolar depression?
Worked example
A student writes: ‘Oruč et al. proved that a serotonin-gene variant causes unipolar depression.’ Correct the claim using the original study.
Show the worked solution
- Check the diagnosis of the study participants in the original article, not only the syllabus heading.
- Separate the full-sample result from the female subgroup trends.
- State what the association can and cannot establish.
Answer The original article studied 42 people with bipolar I and 40 healthy controls, not a unipolar-depression sample. It found no significant association in the full patient group; the sex-divided analysis reported tentative trends in women. The study cannot prove that a variant causes unipolar depression or predict an individual's risk.
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Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
A learner claims that Oruč et al. (1997) prove inherited serotonin variants cause unipolar depression. Write a corrected two-sentence evaluation.
Give me a hint
Compare the syllabus placement with the original article's participants and results.
Compare my reasoning
- The syllabus places Oruč et al. in its unipolar-depression explanations, but the original article studied 42 patients with bipolar I and 40 healthy controls.
- The study found no significant association in the full patient sample; female subgroup trends were tentative and associational.
- It cannot prove a cause of unipolar depression or predict an individual's risk.
The syllabus lists Oruč et al. in the unipolar section, but the original article reports a bipolar-I sample of 42 patients and 40 controls. There was no significant association in the full sample; subgroup trends in women are tentative. The result cannot prove that a gene causes unipolar depression or predict an individual outcome.
Look for these in your work
- Syllabus and primary source distinguished
- Sample and result reported accurately
- Causal and individual claims limited
Apply Beck’s cognitive theory and learned helplessness to a fictional student who fails one quiz and thinks, ‘I am bad at every subject; nothing I do will help.’ Then give one limitation of the explanation.
Give me a hint
Identify the event, the broad self-judgement and the expectation that action cannot change the outcome.
Compare my reasoning
- The quiz result is one event; interpreting it as proof of failure in every subject resembles an overgeneralised negative belief about the self and world, while ‘nothing will help’ is a hopeless future expectation.
- The statement also resembles an internal, stable and global attribution for a negative event, which can make the outcome seem uncontrollable in the learned-helplessness reformulation.
- This fictional example illustrates theories only. One thought after one quiz cannot diagnose depression or establish why a real student feels distressed; context, other explanations and professional support may matter.
Beck’s account would examine the student's negative interpretation and broad belief about self, experience and future. Learned helplessness would focus on the expectation that actions cannot change outcomes and the internal, stable, global explanation. These are possible theoretical readings of a fictional statement, not evidence of a diagnosis or a complete cause.
Look for these in your work
- Event separated from interpretation
- Both theories applied accurately
- No diagnosis inferred from one statement
Design a brief ethical study testing whether explanatory style predicts changes in mood over time. State a sample, two measurements, one analysis and one limitation.
Give me a hint
Observe naturally occurring responses over time; do not induce depression or withhold care.
Compare my reasoning
- Recruit consenting adults who can choose to stop, and use an established explanatory-style measure and a validated mood measure at baseline and at a later follow-up; do not recruit or label people based on a lesson exercise.
- Record whether baseline explanatory-style scores predict later mood scores after accounting for baseline mood, and report the measure, timing and analysis clearly.
- A prospective association would improve temporal ordering but would not prove that attributional style causes mood change; unmeasured events and measurement limits remain possible. Protect privacy and provide appropriate support information if assessment raises concern.
A prospective study could measure explanatory style and mood at baseline, then repeat the mood measure later. A relationship would show prediction over time in that sample, not causation; experiences between measurements and measurement validity could explain the result. Ethical safeguards include consent, withdrawal, privacy and a support plan.
Look for these in your work
- Two constructs and time points specified
- Association not mistaken for cause
- Consent, privacy and participant support considered
Common mistakes
- Presenting low serotonin as an established single cause of depression
- Claiming that a treatment's biological action proves the original cause of a condition
- Describing Oruč et al. (1997) as a unipolar-depression study when its original article reports bipolar-I participants
- Turning subgroup trends from a small sample into a causal or individual prediction
- Treating Beck’s cognitive triad as a diagnostic checklist
- Saying Seligman et al. (1988) proved that attributional style caused improvement during therapy
- Using a theory of helplessness to blame a person for their circumstances
What can you explain now?
What is the most important source-evaluation limitation when using Oruč et al. (1997) for this syllabus section?
Compare with the explanation
The syllabus lists the study in its unipolar-depression explanations, but the original study sampled people with bipolar I disorder and healthy controls.
This mismatch means the study must not be described as direct evidence about a unipolar-depression sample; its findings also remain tentative and non-causal.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
State one biochemical, one genetic and one cognitive explanation of unipolar depression, then explain why the original Oruč et al. (1997) paper needs a source caveat.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.