Introduction to Psychology · Psychological Disorders

Anxiety, OCD, Trauma, and Mood Disorders

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In 30 seconds
Why this matters
The college version
Eli explains
Worked example
Key takeaway
Study tools

In 30 seconds

involve excessive, persistent fear or worry that impairs functioning: generalized anxiety disorder (), , , and . Obsessive-compulsive disorder (OCD) features intrusive and repetitive . Post-traumatic stress disorder () can follow trauma. include and bipolar disorders, involving depressive and/or manic episodes. These conditions are best understood biopsychosocially, overlap frequently, and require professional evaluation.

Why this matters

These are among the most common conditions in primary care, counseling centers, and schools. Recognizing that persistent, impairing anxiety or mood changes warrant professional evaluation — rather than dismissal as "just stress" or "weakness" — supports timely help-seeking. Person-first language and awareness that effective treatments exist reduce stigma. Because symptoms overlap and can signal medical conditions too, referral to a qualified professional is the appropriate step.

The college version

1. Anxiety Disorders

Anxiety disorders are marked by excessive, persistent fear or worry that impairs functioning:

Generalized anxiety disorder (GAD) — chronic, uncontrollable worry about many everyday topics, with muscle tension and restlessness.
Panic disorder — recurrent, unexpected panic attacks (surges of intense fear with racing heart, shortness of breath) plus fear of more attacks.
Phobias — intense, persistent fear of a specific object or situation, out of proportion to actual danger, leading to avoidance.
Social anxiety disorder — intense fear of being judged or negatively evaluated in social situations, leading to avoidance.

OCD features obsessions (intrusive, unwanted, distressing thoughts or urges) and compulsions (repetitive behaviors or mental acts performed to reduce the distress the obsessions cause); the temporary relief reinforces the cycle. Trauma- and stressor-related disorders arise after exposure to a traumatic or stressful event; the best known is PTSD, which can include intrusive re-experiencing (flashbacks, nightmares), avoidance of reminders, negative changes in mood and thinking, and heightened arousal (hypervigilance, exaggerated startle). PTSD is a normal response to abnormal events, not weakness.

3. Mood Disorders

Mood disorders involve persistent disturbances in emotion that impair functioning. Major depressive disorder (MDD) features one or more depressive episodes — at least two weeks of depressed mood or loss of interest/pleasure, plus changes in sleep, appetite, energy, and concentration. Bipolar disorders involve swings between depressive episodes and manic episodes — distinct periods of abnormally elevated or irritable mood with increased energy, decreased need for sleep, grandiosity, and impulsivity (a milder form is hypomania). Episodes are states; MDD and are the diagnoses.

How it works

A person experiences persistent, impairing fear, worry, intrusive thoughts, or mood changes.
These reflect a mix of biological, psychological, and social contributors.
A clinician assesses duration, intensity, and impairment and uses differential diagnosis to sort through .
If a disorder is diagnosed, an evidence-based plan (CBT, exposure, medication) is developed with the person.
Crisis and safety concerns are addressed first and referred to emergency or crisis services.

Common confusions

Do not confuse	With	Difference
Normal anxiety/sadness	An anxiety or mood disorder	Disorders add persistence, intensity, and impairment
A panic attack	Panic disorder	An attack is one event; the disorder adds recurrence and fear of attacks
Obsessions	Compulsions	Obsessions are thoughts; compulsions are the actions taken to relieve them
Major depressive disorder	Bipolar disorder	MDD has depressive episodes only; bipolar includes manic/hypomanic episodes
Depressive episode	Major depressive disorder	The episode is a state; the disorder is the recurrent diagnosis

Memory aids

For the four anxiety disorders: "General, Panic, Phobia, Social — anxiety keeps Getting People Persistently Stuck." For OCD: "Obsession = Oh no (thought); Compulsion = Calming action."

Quick review

Topic Recap

Anxiety disorders (GAD, panic disorder, phobias, social anxiety disorder) involve excessive, impairing fear or worry. OCD runs on the obsessions–compulsions cycle, and PTSD can follow trauma. Mood disorders include major depressive disorder and bipolar disorders, distinguished by depressive versus manic episodes. All are best explained by interacting biopsychosocial contributors, and symptom overlap makes professional differential diagnosis essential. Evidence-based treatments exist, but this material is educational only — acute crisis and safety concerns require emergency services or qualified professional care, never study notes.

Knowledge Check

How does GAD differ from panic disorder?
Why do compulsions maintain OCD despite giving only temporary relief?
What distinguishes bipolar disorder from major depressive disorder?
Name three symptom groups seen in PTSD.
Why is differential diagnosis especially important across anxiety and mood disorders?

Answers and Rationales

GAD is chronic, diffuse worry about many topics; panic disorder features recurrent unexpected panic attacks plus fear of future attacks.
Compulsions give short-term relief from obsessive distress, which negatively reinforces them and keeps the cycle going.
Bipolar disorder includes manic (or hypomanic) episodes; MDD involves depressive episodes only.
Intrusive re-experiencing, avoidance of reminders, negative changes in mood/cognition, and heightened arousal/hypervigilance.
These disorders share many symptoms and are highly comorbid, so accurate treatment depends on sorting them apart.

Eli explains

The same idea, in plain words

Explain it like I’m 10

Think of your body's alarm system. A smoke alarm helps when there is real smoke; an anxiety disorder is an alarm that keeps going off when there is no fire. The alarm itself — racing heart, worry, alertness — is a normal protective response; the disorder is an alarm too sensitive, too loud, or unable to shut off.

Where it stops being exact: this makes disorders sound like merely "too much" normal emotion. In reality they also involve brain systems, learning history, and life circumstances, and two people with the same diagnosis can have very different causes.

Simple Example

Jamal washes his hands until they are raw because a persistent thought ("my hands are contaminated") will not quiet down unless he washes. The thought is an obsession; the washing is a compulsion that temporarily reduces the anxiety — which is why the cycle keeps repeating.

Worked example

These conditions are best explained by biopsychosocial contributors — interacting biological (genetics, brain circuits, neurotransmitters), psychological (learning, cognitive styles), and social (stress, trauma, culture, support) factors. These are largely correlational patterns: co-occurrence does not by itself prove causation. Symptom overlap complicates diagnosis — anxiety and depression frequently co-occur, irritability appears in both depression and bipolar disorder, and intrusive thoughts occur in both OCD and PTSD — so accurate diagnosis requires a trained clinician, not a self-check list.

Evidence-based treatment overview (education only): research-supported approaches include cognitive-behavioral therapy (CBT) with exposure for anxiety and OCD, trauma-focused therapies for PTSD, and medication (e.g., antidepressants, mood stabilizers) for mood disorders. This overview is educational, not a recommendation for any specific person. Crisis/referral boundaries: if a person is in immediate danger of harming themselves or others, or in acute crisis, they need local emergency services, crisis hotlines, or a qualified professional immediately — not study notes.

Key takeaways

High yield: Anxiety disorders share excessive fear/worry but differ in focus (GAD = general, panic = attacks, phobia = specific object, social = evaluation).
High yield: In OCD, compulsions temporarily relieve obsessional distress, reinforcing the cycle.
High yield: Bipolar disorder is distinguished from MDD by manic (or hypomanic) episodes.
PTSD is a normal reaction to abnormal events, not weakness.
Symptom overlap and comorbidity make differential diagnosis essential.

Keep learning

Ready to build on this? Continue to the next lesson.

Study toolsYou’ll learn to · Key vocabulary

You’ll learn to

Distinguish the major anxiety disorders and their shared and unique features.
Explain OCD, including the relationship between obsessions and compulsions.
Describe trauma- and stressor-related disorders, especially PTSD.
Contrast major depressive disorder and bipolar disorders, and identify crisis and referral boundaries.

Key vocabulary

Anxiety disorders: Excessive, persistent fear/worry that impairs function
GAD: Chronic, uncontrollable worry about many topics
Panic disorder: Recurrent unexpected panic attacks plus fear of more
Phobias: Intense fear of specific objects/situations
Social anxiety disorder: Fear of negative evaluation in social situations
Obsessions: Intrusive, unwanted, distressing thoughts/urges
Compulsions: Repetitive acts done to reduce obsessive distress
Trauma/stressor disorders: Conditions after traumatic/stressful events
PTSD: Re-experiencing, avoidance, negative mood, hyperarousal
Mood disorders: Persistent disturbances in emotion
Major depressive disorder: One or more depressive episodes
Bipolar disorder: Episodes of depression and mania
Manic episode: Elevated/irritable mood + energy, less sleep, impulsivity
Depressive episode: Two-plus weeks depressed mood/loss of interest + symptoms
Biopsychosocial contributors: Combined biological, psychological, social causes
Symptom overlap: Shared symptoms across disorders

Educational content only. It is not medical, legal or professional advice. Found an error? Tell us.