Difficulty: Intermediate | Prerequisites: Introduction to abnormal psychology, basic familiarity with the DSM-5 classification system.
This material sits in the clinical psychology and abnormal behaviour unit of AP Psychology. It covers five major disorders through a case-study lens, which is exactly how the AP exam tests diagnostic reasoning. You need to know each disorder's hallmark symptoms, the DSM-5 criteria that distinguish one from another, and how to apply those criteria to a patient vignette. If you are fuzzy on what the DSM-5 is or how anxiety disorders differ from mood disorders at a high level, review your introductory abnormal psychology notes first.
Five clinical case studies illustrate how to match patient symptoms to DSM-5 diagnoses. The disorders covered are panic disorder (sudden physical fear responses with no medical cause), OCD (rigid rituals driven by intrusive thoughts), dissociative fugue (trauma-triggered memory blackouts with unexpected travel), schizophrenia (delusions, hallucinations, disorganised behaviour), and bipolar disorder (cycling between depressive lows and manic highs). The core skill tested is reading a symptom list and identifying the correct diagnosis, including the rationale that rules out alternatives.
Panic Disorder
An anxiety disorder marked by recurrent, unexpected panic attacks and persistent worry about future attacks or their consequences.
Think of it as: your body's fight-or-flight alarm going off at full blast for no apparent reason, repeatedly.
Panic Attack
A discrete episode of intense fear or discomfort that peaks within minutes, accompanied by physical symptoms such as racing heart, chest pain, sweating, nausea, and dizziness.
In simple terms, this means a sudden wave of physical terror that feels like a heart attack but has no cardiac cause.
Obsessive-Compulsive Disorder (OCD)
A disorder characterised by persistent, unwanted thoughts (obsessions) and repetitive behaviours or mental acts (compulsions) performed to reduce the anxiety those thoughts cause.
Think of it as: a mental loop where an intrusive thought creates anxiety, a ritual temporarily relieves it, and the cycle repeats.
Obsessions
Recurrent, intrusive, unwanted thoughts, urges, or images that cause marked anxiety or distress.
In simple terms, this means thoughts that force their way in and will not leave, no matter how much the person wants them gone.
Compulsions
Repetitive behaviours or mental acts that a person feels driven to perform in response to an obsession, often following rigid rules.
Think of it as: the rituals people do to quiet the obsessive thought, even though they know the ritual is excessive.
Dissociative Fugue
A subtype of dissociative amnesia involving sudden, unexpected travel away from home or work, accompanied by inability to recall one's past and sometimes confusion about personal identity.
In simple terms, this means a person "comes to" in an unfamiliar place with no memory of how they got there, usually triggered by severe stress or trauma.
Dissociative Amnesia
An inability to recall important autobiographical information, usually of a traumatic or stressful nature, that is inconsistent with ordinary forgetting.
Think of it as: the mind protecting itself by blocking out memories too painful to process, going well beyond normal forgetfulness.
Schizophrenia
A severe psychotic disorder characterised by delusions, hallucinations, disorganised speech and behaviour, and negative symptoms (e.g. flat affect, avolition), lasting at least six months.
In simple terms, this means a condition where someone loses contact with reality through false beliefs, sensory experiences that are not real, and difficulty organising thoughts or behaviour.
Delusions
Fixed, false beliefs that persist despite contradictory evidence and are not accounted for by the person's cultural or religious background.
Think of it as: believing something with absolute certainty even when every piece of evidence says otherwise.
Hallucinations
Sensory experiences that occur without external stimulation, most commonly auditory (hearing voices) in schizophrenia.
In simple terms, this means seeing, hearing, or feeling things that are not there.
Bipolar Disorder
A mood disorder characterised by alternating episodes of mania (or hypomania) and depression.
Think of it as: mood swings that go far beyond normal ups and downs, cycling between extreme highs and debilitating lows.
Manic Episode
A distinct period of abnormally elevated, expansive, or irritable mood and increased energy, lasting at least seven days, with symptoms such as decreased need for sleep, grandiosity, pressured speech, and risky behaviour.
In simple terms, this means a stretch of days where someone feels invincible, barely sleeps, and acts impulsively in ways that can cause serious harm.
DSM-5
The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, published by the American Psychiatric Association. It is the standard classification system used in the United States for diagnosing mental disorders.
Think of it as: the reference book clinicians use to match a patient's symptoms to a recognised diagnosis.
Tags: panic disorder, panic attack, anxiety disorder, DSM-5 panic criteria, somatic symptoms, fight-or-flight
Hallmark symptoms
Recurrent, unexpected panic attacks (not triggered by an obvious cue)
Intense fear peaking within minutes
Physical symptoms during the attack: racing heart, chest pain, sweating, nausea, dizziness, trembling, shortness of breath
At least one month of persistent concern about additional attacks, worry about the implications of the attack (e.g. "Am I having a heart attack?"), or significant behavioural change related to the attacks
Key diagnostic reasoning (from Case 1, Kristin)
Kristin presents with excessive worry, difficulty concentrating, sudden unexplained attacks of fear, and a cluster of physical symptoms (racing heart, chest pain, sweating, nausea, dizziness)
A medical exam found no cardiac abnormality, which rules out a physical cause and supports a psychological diagnosis
Stressful life events (family problems, starting college) can trigger or worsen panic disorder
The fact that patients often believe they are having a heart attack during a panic attack is a classic feature the exam will test
Differential diagnosis pointers
Generalised anxiety disorder (GAD) involves chronic, pervasive worry but lacks the sudden, discrete panic attacks
Specific phobia involves panic-like symptoms, but only in response to a specific feared object or situation
Medical conditions (cardiac arrhythmias, hyperthyroidism) must be excluded before diagnosing panic disorder, which is why the clean medical exam matters
Tags: OCD, obsessive-compulsive disorder, obsessions, compulsions, rituals, anxiety reduction, bedtime routine, DSM-5 OCD criteria
Core feature: the obsession-compulsion cycle
An intrusive, unwanted thought (obsession) creates anxiety
The person performs a ritual or behaviour (compulsion) to reduce that anxiety
Relief is temporary, so the cycle repeats and often escalates
Both obsessions and compulsions must be present for a full OCD diagnosis under the DSM-5
The behaviours are time-consuming (often taking more than one hour per day) or cause clinically significant distress or impairment
Key diagnostic reasoning (from Case 2, Shelby)
Shelby's bedtime routine is rigid and elaborate: exactly one hour of journaling, picking hair and lint from the bed, 10 to 30 minutes brushing and flossing, requiring every family member to respond to her goodnight call
If someone does not respond, she repeats the entire ritual, even waking from sleep to do so
The routine disrupts her own sleep and her family's sleep, demonstrating functional impairment
The "need" for a specific response from others and the inability to stop the ritual without extreme distress point to compulsive behaviour driven by underlying obsessive thoughts
What distinguishes OCD from normal habits
Everyone has routines, but OCD routines are ego-dystonic (the person recognises them as excessive or irrational but cannot stop)
The behaviour causes distress or significant interference with daily life
Obsessive-compulsive personality disorder (OCPD) is a separate diagnosis involving a pervasive pattern of perfectionism and control that the person often sees as reasonable, unlike OCD where the person typically knows their behaviour is excessive
Tags: dissociative fugue, dissociative amnesia, dissociative disorders, blackouts, trauma-triggered amnesia, identity confusion, DSM-5 dissociative criteria
Core features
Sudden, unexpected travel away from home or one's usual environment
Inability to recall one's past during the episode
Possible confusion about personal identity or assumption of a new identity
Episodes are typically triggered by severe psychological stress or trauma
In the DSM-5, dissociative fugue is classified as a specifier of dissociative amnesia rather than a standalone diagnosis
Key diagnostic reasoning (from Case 3, Carl)
Carl has experienced "blackouts" over six months
The first blackout followed a traumatic event involving his wife and a coworker
During blackouts, he cannot remember what happened
At least one episode involved travel to a location far from home, which is the hallmark that distinguishes fugue from simple dissociative amnesia
The pattern of several episodes over time, each linked to psychological stress, supports a dissociative disorder
How fugue differs from other memory problems
Unlike ordinary amnesia (from head injury or substance use), dissociative fugue has no identifiable neurological or substance-related cause
Unlike dissociative identity disorder (formerly multiple personality disorder), fugue does not involve the emergence of distinct alternate identities with their own histories
The travel component is what separates fugue from dissociative amnesia without fugue
Tags: schizophrenia, psychotic disorder, delusions, hallucinations, disorganised behaviour, disorganised speech, positive symptoms, negative symptoms, brief psychotic disorder
Positive symptoms (additions to normal experience)
Delusions: fixed false beliefs (e.g. believing people in hamburgers are controlling you)
Hallucinations: sensory perceptions without external stimuli, most commonly auditory
Disorganised speech: incoherent, tangential, or loosely associated verbal output
Disorganised or catatonic behaviour: unpredictable agitation, bizarre actions, or complete immobility
Negative symptoms (reductions in normal functioning)
Flat affect (reduced emotional expression)
Avolition (lack of motivation)
Alogia (poverty of speech)
Anhedonia (inability to experience pleasure)
Key diagnostic reasoning (from Case 4, Lyndsi)
Lyndsi attempted self-harm while exhibiting clear psychotic symptoms
She was screaming about "people in hamburgers making her cut," which indicates delusional thinking
She was agitated, talking about "them" (possible paranoid ideation or hallucinations)
Her behaviour was disorganised (unresponsive to the manager, then agitated)
The combination of delusions, probable hallucinations, and disorganised behaviour points to a psychotic disorder
Substance use and medical conditions must be ruled out before confirming schizophrenia
If symptoms have lasted less than six months, a brief psychotic disorder or schizophreniform disorder may be the more accurate diagnosis
Why the exam distinguishes schizophrenia from brief psychotic disorder
Schizophrenia requires symptoms lasting at least six months (with at least one month of active-phase symptoms)
Brief psychotic disorder lasts between one day and one month, with full return to premorbid functioning
The AP exam may give a vignette with limited duration information to test whether you raise this distinction
Tags: bipolar disorder, manic episode, mania, depressive episode, mood disorder, elevated mood, impulsivity, disinhibition, DSM-5 bipolar criteria
Manic episode criteria (DSM-5)
Abnormally elevated, expansive, or irritable mood plus increased energy or activity, lasting at least seven days (or any duration if hospitalisation is required)
At least three of the following (four if mood is only irritable): inflated self-esteem or grandiosity, decreased need for sleep, pressured speech, flight of ideas, distractibility, increased goal-directed activity or psychomotor agitation, excessive involvement in risky activities
Key diagnostic reasoning (from Case 5, Becky)
Becky was found running naked through a public park, which demonstrates severe disinhibition and impaired judgement
She became combative with law enforcement, showing agitation and possible grandiosity or irritability
She exhibited hissing and spitting behaviour (disorganised and inappropriate)
During a later interview, she was excitable and pleasant, consistent with elevated mood
She mentioned feeling down for two weeks before the incident, suggesting a preceding depressive episode
The combination of a depressive phase followed by a manic phase is the defining pattern of bipolar disorder
Substance use and medical conditions (e.g. hyperthyroidism) must still be excluded
Bipolar I vs Bipolar II (exam-relevant distinction)
Bipolar I requires at least one full manic episode. Depressive episodes are common but not required for diagnosis
Bipolar II involves hypomanic episodes (less severe, shorter duration, no psychotic features, no hospitalisation) plus at least one major depressive episode
Becky's presentation, with severe mania leading to law enforcement involvement, is consistent with Bipolar I
Students often confuse panic disorder with generalised anxiety disorder. GAD involves chronic, free-floating worry across many domains, whereas panic disorder centres on discrete, sudden attacks with intense physical symptoms. If the vignette describes sudden episodes that peak and subside, think panic disorder.
Students often think OCD is just "being neat" or "liking things tidy." It is not. OCD involves distressing, intrusive thoughts and time-consuming rituals that interfere with daily life. A person who simply prefers an organised desk does not meet criteria.
Students sometimes assume dissociative fugue means the person has "multiple personalities." Fugue involves amnesia and unexpected travel, not the presence of distinct alternate identities. That is dissociative identity disorder, a separate diagnosis.
Students frequently believe that schizophrenia means "split personality." The word's Greek roots ("split mind") are misleading. Schizophrenia is a psychotic disorder involving delusions, hallucinations, and disorganised thinking. It has nothing to do with having multiple personalities.
The AP exam frequently presents case vignettes and asks you to identify the most likely diagnosis. Practise reading a symptom list and mapping it to DSM-5 criteria rather than relying on gut feeling.
A clean medical exam in a vignette is a strong signal that the condition is psychological. If the question mentions "tests came back normal," the answer is almost certainly not a medical condition.
The distinction between obsessions (thoughts) and compulsions (behaviours) is heavily tested. Know which is which and be able to identify both in a case study.
Expect at least one question requiring you to distinguish between disorders with overlapping symptoms: panic disorder vs GAD, schizophrenia vs brief psychotic disorder, bipolar mania vs schizophrenia, dissociative fugue vs dissociative identity disorder.
The depressive component of bipolar disorder is commonly tested. If a vignette mentions a prior depressive episode followed by manic symptoms, bipolar disorder is the answer, not unipolar depression.
Dissociative fugue is rare but exam-friendly because it has a distinctive symptom profile (amnesia plus unexpected travel). If travel and memory loss appear together, fugue is the answer.
True or False: Panic disorder requires the presence of a specific phobic trigger for each attack.
Answer: False. Panic attacks in panic disorder are unexpected and not tied to a specific trigger.
Fill in the blank: In OCD, the unwanted intrusive thoughts are called _______ and the repetitive behaviours performed to reduce anxiety are called _______.
Answer: obsessions; compulsions.
True or False: Dissociative fugue always involves the person adopting a completely new identity.
Answer: False. Confusion about identity is possible but not required. The key features are amnesia and unexpected travel.
Fill in the blank: The DSM-5 requires symptoms lasting at least _______ for a diagnosis of schizophrenia.
Answer: six months.
True or False: A person experiencing a manic episode always feels euphoric and happy.
Answer: False. Manic mood can be elevated or irritable. Some manic episodes are characterised primarily by irritability and agitation rather than euphoria.
Q: A college student reports sudden episodes of racing heart, chest tightness, sweating, and an overwhelming fear of dying. Medical tests reveal no cardiac issues. What is the most likely diagnosis?
A: Panic disorder. The sudden onset of intense physical symptoms with no medical explanation, combined with fear of dying during episodes, fits the DSM-5 criteria for panic disorder.
Q: A patient spends two hours each night checking that every door and window is locked, returning to check again even after confirming they are secure. She recognises the behaviour is excessive but cannot stop. What disorder does this suggest?
A: Obsessive-compulsive disorder (OCD). The repetitive checking (compulsion) driven by anxiety she cannot control, despite recognising it as excessive, is characteristic of OCD.
Q: What distinguishes dissociative fugue from dissociative amnesia without fugue?
A: Dissociative fugue involves sudden, unexpected travel away from home or one's usual environment in addition to the amnesia. Dissociative amnesia without fugue involves memory gaps but no purposeful travel.
Q: A patient believes that television news anchors are sending her coded messages and hears voices commenting on her actions. What category of disorder do these symptoms indicate?
A: A psychotic disorder, most likely schizophrenia. The belief about coded messages is a delusion (specifically a referential delusion), and hearing voices is an auditory hallucination. Both are positive symptoms of psychotic disorders.
Q: How does the DSM-5 distinguish between Bipolar I and Bipolar II disorder?
A: Bipolar I requires at least one full manic episode (which may or may not be accompanied by depressive episodes). Bipolar II requires at least one hypomanic episode and at least one major depressive episode, with no history of full mania.
Q: A patient who was feeling depressed for two weeks is now running through public spaces, speaking rapidly, sleeping very little, and making impulsive financial decisions. What is the most likely diagnosis?
A: Bipolar I disorder, currently in a manic episode. The shift from a depressive period to behaviour consistent with mania (disinhibition, decreased sleep, impulsivity) is the hallmark pattern.
Q: Why is it important that a vignette mentions a normal medical exam when diagnosing panic disorder?
A: Because the DSM-5 requires that symptoms are not attributable to the physiological effects of a substance or another medical condition. A normal medical exam rules out physical causes such as cardiac arrhythmia or hyperthyroidism, supporting a psychological diagnosis.
Q: A man is found 200 miles from his home with no memory of how he got there. The episode began after he discovered his partner's infidelity. What diagnosis should you consider?
A: Dissociative fugue (a specifier of dissociative amnesia). The combination of trauma-triggered amnesia and unexpected travel to a distant location is the defining feature.
This material connects directly to the biopsychosocial model, which explains how biological predispositions, psychological patterns, and social stressors interact to produce these disorders. If you are studying the biopsychosocial perspective on depression or schizophrenia, the case-study reasoning here uses the same framework in reverse: identifying which factors in the vignette point to a given diagnosis.
It also connects to the broader topic of diagnostic labelling, including the benefits (shared clinical language, treatment planning) and drawbacks (stigma, oversimplification) of assigning psychiatric diagnoses. The AP exam sometimes asks you to evaluate the use of diagnostic labels, not just apply them.
Finally, treatment approaches for each disorder link back here: CBT and SSRIs for panic disorder and OCD, antipsychotics for schizophrenia, mood stabilisers (e.g. lithium) for bipolar disorder. Knowing the diagnosis is the first step toward knowing the treatment.
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