How do psychologists define, explain, and classify psychological disorders?
Topic 5.3 Explaining and Diagnosing Psychological Disorders: explain how psychological disorders are defined and classified, the diagnostic systems (DSM and ICD), and the models used to explain disorders, including the biopsychosocial and diathesis-stress models.
A focused answer to AP Psychology Topic 5.3, covering how psychological disorders are defined (deviance, distress, dysfunction), the DSM and ICD diagnostic systems, the medical, psychodynamic, behavioral, cognitive, humanistic, and sociocultural perspectives, the biopsychosocial and diathesis-stress models, and the risks of labeling.
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What this topic is asking
Topic 5.3 covers how psychologists define, explain, and classify psychological disorders. The College Board wants the criteria for a disorder, the diagnostic systems (DSM, ICD), the theoretical perspectives that explain disorders, the biopsychosocial and diathesis-stress models, and the risks of labeling.
Defining a disorder
Classifying disorders
Perspectives that explain disorders
The course's major perspectives each offer a different account of why disorders arise:
- Medical (biological): disorders are illnesses with biological causes (genes, neurotransmitters, brain structure).
- Psychodynamic: disorders stem from unconscious conflict.
- Behavioral: disorders are learned responses, acquired through conditioning.
- Cognitive: disorders arise from maladaptive thoughts and beliefs.
- Humanistic: disorders reflect a blocked drive toward growth or a poor self-concept.
- Sociocultural: disorders are shaped by social and cultural context.
Integrative models and labeling
Two models combine these perspectives:
- Biopsychosocial model: disorders result from the interaction of biological, psychological, and social factors.
- Diathesis-stress model: a person develops a disorder when a predisposition (the diathesis, often genetic) is combined with significant environmental stress. Neither alone is enough.
Diagnostic labels aid communication and treatment, but the exam expects awareness of their risks: labels can produce stigma, bias how others perceive a person, and even shape the labeled person's own behavior.
This topic is the conceptual gateway to the rest of the unit, because it sets up the vocabulary used to discuss every specific disorder. The connective idea is that defining and explaining disorders is genuinely difficult: the line between normal and disordered depends on cultural norms and on multiple criteria, and no single perspective fully explains any disorder. That is why the biopsychosocial and diathesis-stress models, which integrate causes, are the safest answers in an FRQ. The diathesis-stress model in particular is heavily tested because it elegantly captures the nature-and-nurture interaction from Unit 3: a genetic vulnerability may stay dormant until life stress activates it. Keeping the definitional criteria, the classification systems, and the integrative models distinct is the key skill.
Try this
Q1. Name the three criteria commonly used to define a psychological disorder. [2 points]
- Cue. Deviance (departing from cultural norms), distress, and dysfunction (interfering with daily life).
Q2. Explain the diathesis-stress model. [1 point]
- Cue. A disorder develops when a predisposing vulnerability (the diathesis) combines with significant environmental stress; neither alone is sufficient.
Exam-style practice questions
Practice questions written in the style of College Board exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
AP 2024 (style)1 marksMultiple choice. A model proposing that a person develops a disorder only when an inherited predisposition is combined with a significant environmental stressor is known as which of the following? (A) The medical model (B) The diathesis-stress model (C) The behavioral perspective (D) The humanistic perspective (E) The DSMShow worked answer →
The answer is (B) The diathesis-stress model.
The diathesis-stress model holds that a disorder arises from the interaction of a predisposing vulnerability (the diathesis, often genetic) and environmental stress. Neither alone is sufficient; the disorder emerges when both are present.
(A) the medical model views disorders as illnesses with biological causes. (C) the behavioral perspective emphasizes learned behavior. (D) the humanistic perspective emphasizes growth and self-concept. (E) the DSM is a classification manual, not an explanatory model.
AP 2023 (style)4 marksConcept-application free-response question. A clinician evaluates a new client. Explain how EACH of the following applies: the criterion of dysfunction in defining a disorder, the DSM, the biopsychosocial model, and the diathesis-stress model.Show worked answer →
A 4-point concept-application FRQ; one point per term.
Dysfunction (1): a behavior counts toward a disorder when it interferes with daily functioning, one of the criteria (alongside deviance and distress) the clinician weighs.
DSM (1): the Diagnostic and Statistical Manual the clinician uses to classify and diagnose the client's symptoms by standardized criteria.
Biopsychosocial model (1): explaining the disorder as the joint product of biological, psychological, and social factors.
Diathesis-stress model (1): the view that the client's predisposition combined with stressors produced the disorder.
Markers reward each term being correctly defined AND tied to the clinical evaluation.
Related dot points
- Topic 5.4 Categories of Psychological Disorders: describe the major categories of psychological disorders, including anxiety, OCD, depressive and bipolar, schizophrenia spectrum, dissociative, trauma- and stressor-related, feeding and eating, neurodevelopmental, and personality disorders, and their defining symptoms.
A focused answer to AP Psychology Topic 5.4, surveying the major categories of psychological disorders: anxiety disorders, OCD, major depressive and bipolar disorders, schizophrenia spectrum disorders with positive and negative symptoms, dissociative disorders, PTSD, feeding and eating disorders, neurodevelopmental disorders, and personality disorders, with their defining features.
- Topic 5.5 Treatment of Psychological Disorders: describe the major approaches to treatment, including psychodynamic, humanistic, behavioral, cognitive, and biomedical therapies, and the formats and ethics of treatment.
A focused answer to AP Psychology Topic 5.5, covering psychodynamic, humanistic (person-centered), behavioral (exposure, systematic desensitization, token economies), cognitive and cognitive-behavioral therapies, and biomedical treatments including drug therapies, ECT, and TMS, plus treatment formats, the eclectic approach, and therapeutic ethics.
- Topic 5.1 Introduction to Health Psychology: explain stress and stressors, the general adaptation syndrome, the effects of stress on health, and the strategies people use to cope with stress.
A focused answer to AP Psychology Topic 5.1, covering health psychology and the biopsychosocial model, types of stressors, Selye's general adaptation syndrome, the tend-and-befriend response, the effects of chronic stress on the immune and cardiovascular systems, and problem-focused and emotion-focused coping.
- Topic 5.2 Positive Psychology: explain the aims of positive psychology, subjective well-being, the concepts of flow, gratitude, character strengths and virtues, resilience, and posttraumatic growth.
A focused answer to AP Psychology Topic 5.2, covering the aims of positive psychology, subjective well-being and the adaptation-level phenomenon, flow, gratitude, character strengths and virtues, resilience, posttraumatic growth, and the role of positive subjective experiences in flourishing.
- Topic 1.1 Interaction of Heredity and Environment: explain how the interaction of nature and nurture, studied through twin, family, and adoption research, shapes psychological traits.
A focused answer to AP Psychology Topic 1.1, covering the nature-nurture interaction, heritability, the evolutionary perspective, and how twin, family, and adoption studies let psychologists separate genetic from environmental influences on behavior.
Sources & how we know this
- AP Psychology Course and Exam Description — College Board (2024)