Premed · Premed · Introductory Psychology
Lecture 23: Psychological Disorders: Anxiety and Mood
Introductory Psychology
Learning Objectives
By the end of this lecture, students will be able to:
- Define psychological disorder and explain the criteria used to distinguish normal from abnormal behavior
- Describe the DSM classification system and the biopsychosocial model of mental illness
- Identify the major anxiety disorders and explain their symptoms, causes, and cognitive-behavioral features
- Describe the key features of obsessive-compulsive and trauma-related disorders
- Explain the symptoms, subtypes, and theories of major depressive disorder and bipolar disorder
Lecture Content
I. Defining Psychological Disorders
A psychological disorder is a syndrome characterized by a clinically significant disturbance in cognition, emotion regulation, or behavior that reflects a dysfunction in psychological, biological, or developmental processes and is associated with significant distress or disability in important areas of functioning. Clinicians evaluate abnormality using the "4 Ds": deviance (behavior that deviates significantly from cultural norms or statistical averages), distress (personal suffering experienced by the individual), dysfunction (interference with daily functioning in work, relationships, or self-care), and danger (risk to self or others, though this is the least common criterion, as most people with mental disorders are not dangerous). No single criterion is sufficient; clinical judgment considers the overall pattern.
Cultural considerations are essential, since what counts as abnormal varies across cultures and historical periods. Culture-bound syndromes are disorders specific to particular cultures — taijin kyofusho in Japan, for example, involves an intense fear of offending others. Culturally sensitive diagnosis is necessary to avoid pathologizing normal cultural variation. The medical model views psychological disorders as illnesses with biological causes that can be diagnosed and treated. This framework reduces blame and encourages treatment-seeking but has been criticized for potentially over-medicalizing normal human variation and underemphasizing social and cultural factors.
II. Classification: The DSM
The Diagnostic and Statistical Manual of Mental Disorders (DSM-5-TR), published by the American Psychiatric Association, is the standard classification system in North America. It provides diagnostic criteria, descriptions, and prevalence data for each disorder and is organized into chapters by disorder categories. Classification serves several purposes: it facilitates communication among professionals, guides treatment decisions, supports research, and aids in insurance and legal proceedings.
Classification has its critics. Labeling effects mean that a diagnosis can become a self-fulfilling prophecy and carry social stigma. Rosenhan's 1973 study, in which pseudopatients gained admission to psychiatric hospitals by reporting auditory hallucinations, demonstrated that once labeled, normal behaviors were interpreted through the lens of the diagnosis. The categorical-versus-dimensional debate questions whether disorders are discrete categories or points on a continuum. High rates of comorbidity — the co-occurrence of multiple disorders — further challenge clean categorization.
The biopsychosocial model provides the most comprehensive framework, recognizing that disorders arise from the interaction of biological factors (genetics, brain chemistry, prenatal influences), psychological factors (learned behaviors, cognitive patterns, personality, trauma), and social factors (poverty, discrimination, family dysfunction, cultural stressors). The diathesis-stress model adds specificity: a person carries a predisposition (diathesis) that interacts with environmental stressors to trigger a disorder. Typically, neither diathesis nor stress alone is sufficient.
<image>A multi-panel figure on the classification and conceptualization of psychological disorders. Panel A: A Venn diagram of the "4 Ds" — four overlapping circles labeled Deviance, Distress, Dysfunction, and Danger, with "Psychological Disorder" at the center intersection, and annotations noting that most diagnoses involve the first three but not necessarily danger. Panel B: The biopsychosocial model shown as a triangle with "Biological factors" (genetics, neurotransmitters, brain structure), "Psychological factors" (cognition, learning, personality), and "Social factors" (culture, family, socioeconomic status) at the three vertices, with bidirectional arrows connecting all three and "Psychological Disorder" in the center. Panel C: The diathesis-stress model as a graph with "Stress level" on the x-axis and "Likelihood of disorder" on the y-axis, showing two lines — one for high diathesis (reaching the threshold at lower stress) and one for low diathesis (requiring much higher stress to reach the threshold).</image>
III. Anxiety Disorders
Anxiety is a state of apprehension, tension, and uneasiness about future threats. Normal anxiety is adaptive, motivating preparation and avoidance of genuine danger. Anxiety disorders involve excessive, persistent anxiety that is disproportionate to the actual situation.
Generalized anxiety disorder (GAD) is characterized by chronic, excessive, uncontrollable worry about multiple life domains — health, finances, work, relationships — lasting at least six months. Physical symptoms include muscle tension, restlessness, fatigue, difficulty concentrating, sleep disturbance, and irritability. It affects approximately 3% of the population, is more common in women, and is cognitively characterized by intolerance of uncertainty.
Panic disorder involves recurrent, unexpected panic attacks — sudden surges of intense fear that peak within minutes, accompanied by racing heart, shortness of breath, chest pain, dizziness, trembling, sweating, numbness, derealization, and fear of dying or "going crazy." The disorder includes persistent worry about future attacks and maladaptive behavioral changes. It affects about 2-3% of the population. Agoraphobia, the fear or avoidance of situations where escape may be difficult or help unavailable, often develops alongside panic disorder but can occur independently.
Specific phobias are intense, irrational fears of particular objects or situations — animals, heights, blood-injection-injury, flying, or enclosed spaces. They are the most common anxiety disorder, affecting 7-9% of the population. The blood-injection-injury phobia is unique in producing a vasovagal response (a drop in blood pressure leading to fainting) rather than the typical sympathetic arousal. Social anxiety disorder involves an intense fear of social situations in which one might be scrutinized, evaluated, or embarrassed. Fear of negative evaluation is its defining feature, and it affects approximately 7% of the population, with onset typically in adolescence.
IV. Etiology of Anxiety Disorders
Biological factors include moderate genetic heritability (approximately 30-40%), neurotransmitter imbalances (low GABA, serotonin dysregulation, norepinephrine hyperactivity), and brain circuit abnormalities (an overactive amygdala, underactive prefrontal cortex, and altered hippocampal function). Autonomic nervous system hyperreactivity also contributes.
Psychological factors play equally important roles. Classical conditioning can create phobias through association, as Watson demonstrated with Little Albert. Operant conditioning maintains phobias through avoidance learning: avoidance is negatively reinforced because it reduces anxiety, trapping the individual in a cycle described by Mowrer's two-factor theory. Observational learning allows fear to be acquired by watching others display it. Cognitive factors include attentional bias toward threat, catastrophic misinterpretation of bodily sensations (central to Clark's cognitive model of panic), overestimation of danger, and intolerance of uncertainty. In the cognitive model of panic, normal bodily sensations are catastrophically misinterpreted ("My heart is racing, I must be having a heart attack"), which increases anxiety, amplifies the sensations, and creates a vicious escalating cycle.
Seligman's preparedness theory proposes that humans are biologically prepared to fear stimuli that posed threats throughout evolutionary history — snakes, spiders, heights, and darkness — which explains why some phobias are far more common than others despite equivalent opportunities for conditioning.
<image>A multi-panel figure on anxiety disorders. Panel A: The cognitive model of panic disorder — a circular flowchart showing a triggering stimulus (e.g., physical exertion) leading to a bodily sensation (rapid heartbeat), then catastrophic misinterpretation ("I'm having a heart attack"), then increased anxiety and arousal, which amplifies bodily sensations, forming a vicious cycle. An intervention arrow shows where cognitive therapy breaks the cycle. Panel B: The two-factor model of phobia acquisition and maintenance — Step 1: Classical conditioning (neutral stimulus paired with traumatic event creates conditioned fear), Step 2: Operant conditioning (avoidance of the conditioned stimulus is negatively reinforced by anxiety reduction, maintaining the phobia). Panel C: A bar graph showing lifetime prevalence rates for common anxiety disorders: specific phobia (~9%), social anxiety disorder (~7%), GAD (~3%), panic disorder (~3%), and agoraphobia (~2%), with shading to indicate higher prevalence in women vs. men.</image>
V. Obsessive-Compulsive and Related Disorders
Although separated from anxiety disorders in the DSM-5, obsessive-compulsive and related disorders share anxiety-related features. Obsessive-compulsive disorder (OCD) involves obsessions — persistent, unwanted, intrusive thoughts, images, or urges that cause marked anxiety — and compulsions — repetitive behaviors or mental acts performed to reduce that anxiety. Common obsession themes include contamination, doubt, symmetry, aggressive impulses, and sexual or religious concerns. Common compulsions include hand-washing, checking, counting, ordering, and mental rituals. Individuals with OCD typically recognize that their obsessions and compulsions are excessive but cannot stop them. OCD affects 1-2% of the population equally across sexes and often begins in late adolescence or early adulthood. Neurobiologically, it involves hyperactivity in the orbitofrontal cortex and caudate nucleus (the cortico-striatal-thalamic circuit) and serotonin dysfunction. Body dysmorphic disorder involves preoccupation with perceived physical flaws that are not observable to others, and hoarding disorder involves persistent difficulty discarding possessions, leading to clutter that compromises living space.
VI. Trauma- and Stressor-Related Disorders
Post-traumatic stress disorder (PTSD) develops after exposure to a traumatic event such as combat, assault, disaster, accident, or childhood abuse. Its symptoms cluster into four domains: intrusion (flashbacks, nightmares, intrusive memories), avoidance (avoiding reminders of the trauma), negative alterations in cognition and mood (distorted self-blame, persistent negative emotions, emotional numbing), and arousal and reactivity changes (hypervigilance, exaggerated startle, irritability, sleep and concentration problems). Symptoms must persist for more than one month and cause significant distress or impairment.
PTSD has a lifetime prevalence of roughly 6-9%, is higher in women, and is particularly elevated among combat veterans and assault survivors. Importantly, not everyone exposed to trauma develops PTSD — resilience is the most common outcome. Risk factors include the severity of the trauma, prior mental health problems, lack of social support, and peritraumatic dissociation. Neurobiologically, PTSD involves a hyperactive amygdala, a hypoactive medial prefrontal cortex, and altered hippocampal function that impairs the contextual processing of fear memories.
VII. Depressive Disorders
Major depressive disorder (MDD) requires at least five symptoms present nearly every day for at least two weeks, with at least one being depressed mood or loss of interest and pleasure (anhedonia). Additional symptoms include significant changes in weight or appetite, insomnia or hypersomnia, observable psychomotor agitation or retardation, fatigue, feelings of worthlessness or excessive guilt, difficulty thinking or concentrating, and recurrent thoughts of death or suicidal ideation. MDD affects approximately 7% of the population in any given year and 17% over a lifetime, is about twice as common in women as in men, and is a leading cause of disability worldwide. Most people who experience one episode will have another.
Persistent depressive disorder (dysthymia) is a chronic, lower-grade depression lasting at least two years. It involves fewer symptoms than MDD but greater duration, and it can co-occur with major depressive episodes in a pattern called "double depression."
VIII. Bipolar and Related Disorders
Bipolar I disorder is characterized by at least one manic episode — a distinct period of abnormally elevated, expansive, or irritable mood with increased energy lasting at least seven days (or any duration if hospitalization is required). Manic symptoms include inflated self-esteem or grandiosity, decreased need for sleep, pressured speech, racing thoughts, distractibility, increased goal-directed activity, and excessive involvement in risky behaviors. Mania can include psychotic features such as delusions and hallucinations. Bipolar II disorder involves at least one hypomanic episode (similar to mania but less severe, shorter in duration, and not causing marked impairment) along with at least one major depressive episode. Bipolar disorders affect approximately 1% of the population each, occur equally in men and women, typically begin in late adolescence or early adulthood, and carry a high suicide risk (25-50% attempt suicide over their lifetime).
IX. Etiology of Mood Disorders
Biological factors include strong genetic heritability — approximately 70-80% for bipolar disorder and about 40% for MDD. The monoamine hypothesis implicates low levels of serotonin, norepinephrine, and dopamine in depression, with excess dopamine and norepinephrine in mania. Modern understanding recognizes that this is oversimplified; receptor sensitivity, neural circuits, and neuroplasticity are all involved. Brain structure changes in depression include reduced hippocampal volume, hyperactive amygdala, and underactive prefrontal cortex. HPA axis dysregulation produces elevated cortisol levels, and reduced brain-derived neurotrophic factor (BDNF) impairs neuroplasticity.
Among psychological factors, Beck's cognitive theory identifies the cognitive triad — negative views of the self, the world, and the future — as central to depression. Cognitive distortions such as all-or-nothing thinking, overgeneralization, catastrophizing, and personalization maintain these negative patterns, and negative core beliefs (schemas) are activated by stressful events. Seligman's learned helplessness model, reformulated as the attributional model, proposes that internal, stable, and global attributions for negative events predispose people to depression. Nolen-Hoeksema's work on rumination — the repetitive, passive focus on one's symptoms and their causes — shows that this cognitive style amplifies and prolongs depressive episodes. Social factors include stressful life events, loss, social isolation, poverty, and childhood adversity.
<image>A multi-panel figure on mood disorders. Panel A: Beck's cognitive triad for depression — three boxes connected in a triangle: "Negative view of self" ("I am worthless"), "Negative view of the world" ("The world is unfair"), and "Negative view of the future" ("Things will never improve"), with arrows showing how each reinforces the others, and a surrounding layer labeled "Cognitive distortions" with examples (all-or-nothing thinking, catastrophizing, overgeneralization). Panel B: A timeline comparison of bipolar I and bipolar II mood episodes — a horizontal axis representing time with mood plotted on the vertical axis ranging from severe depression through normal mood to mania. Bipolar I shows full manic peaks and depressive troughs; bipolar II shows hypomanic peaks (below the mania threshold) and depressive troughs. Key features of each phase are annotated. Panel C: A bar graph of heritability estimates for mood disorders: MDD (~40%), bipolar I (~75%), and bipolar II (~70%), alongside a note that concordance rates are higher in identical than fraternal twins.</image>
