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18.7 Biopsychosocial Etiology, Schizophrenia, Mood & Anxiety Disorders

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Medical College Admission Test MCAT

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1 MCAT Architecture, Test-Day Logistics & Scientific Inquiry Skills

1.1 MCAT Architecture, Test-Day Logistics & Scoring Scale (472–528) 1.2 Scientific Inquiry & Reasoning Skills (SIRS 1–4) & Experimental Design 1.3 Passage Navigation, Section Pacing & Strategic Guessing

2 Physics: Mechanics, Fluids & Periodic Motion

2.1 Translational Kinematics, Projectile Motion & Newton's Laws 2.2 Friction, Centripetal Force & Rotational Equilibrium in Biomechanics 2.3 Mechanical Work, Pressure-Volume Work & Forms of Energy 2.4 The Work-Energy Theorem, Power & Mechanical Advantage 2.5 Hydrostatics, Fluid Dynamics & Circulatory Hemodynamics 2.6 Periodic Motion, Wave Fundamentals, Superposition & Standing Waves 2.7 Sound Intensity, the Decibel Scale & the Doppler Effect

3 Physics: Electromagnetism, Optics & Atomic Physics

3.1 Coulomb's Law, Electric Fields & Electric Potential 3.2 Electric Dipoles, Membrane Potentials & the Nernst Equation 3.3 Electric Current, Resistance & Resistor Networks 3.4 Capacitance, Dielectrics & Axonal Cable Theory 3.5 Light, Refraction, Mirrors & Thin Lenses 3.6 The Optical System of the Eye & Corrective Lens Prescriptions 3.7 Nuclear Architecture, Binding Energy & Radioactive Decay Modes 3.8 Decay Kinetics, Half-Life & Medical Radiation Applications

4 General Chemistry: Atoms, Solutions & Thermodynamics

4.1 Quantum Numbers, Electron Configurations & Periodic Trends 4.2 Lewis Structures, Formal Charge, VSEPR Geometry & Molecular Polarity 4.3 States of Matter, Phase Diagrams, Heating Curves & Solvation 4.4 Concentration Units, Henry's Law & Colligative Properties 4.5 Thermodynamic Systems, the First Law, Enthalpy & Entropy 4.6 Gibbs Free Energy, Equilibrium & Bioenergetic Reaction Coupling 4.7 Collision Theory, Transition States & Empirical Rate Laws 4.8 Integrated Rate Laws, Half-Life, Arrhenius Behaviour & Catalysis

5 General Chemistry: Equilibrium, Acids, Bases & Electrochemistry

5.1 Chemical Equilibrium, Equilibrium Constants & Le Chatelier's Principle 5.2 Acid-Base Definitions, pH Scale, Titrations & Physiological Buffers 5.3 Electrochemical Cells, Reduction Potentials & the Nernst Equation

6 Organic Chemistry: Structure, Stereochemistry & Mechanisms

6.1 IUPAC Nomenclature, Functional Group Priority & Orbital Hybridisation 6.2 Resonance, Inductive Effects & Conformational Analysis 6.3 The Isomer Hierarchy, Chirality & CIP Priority Rules 6.4 Optical Activity, Diastereomers, Meso Compounds & Fischer Projections 6.5 Carbonyl Reactivity: Aldehydes, Ketones & Nucleophilic Additions 6.6 Carboxylic Acids & Derivatives: Nucleophilic Acyl Substitution

7 Bio-Organic Reactions, Laboratory Separations & Spectroscopy

7.1 Alcohol Physical Properties, Acidity, Leaving Groups & Protecting Groups 7.2 Carbon Oxidation States, Laboratory Oxidations & Biological Redox Cofactors 7.3 Extraction, Acid-Base Separation & Distillation 7.4 Analytical and Biomacromolecular Chromatography 7.5 Infrared and UV-Vis Spectroscopy 7.6 1H-NMR, 13C-NMR & Integrated Spectral Elucidation

8 Biochemistry: Amino Acids, Peptides & Enzymes

8.1 Amino Acid Stereochemistry & Side-Chain Classification 8.2 Zwitterions, Titration Curves, Isoelectric Points & the Peptide Bond 8.3 The Hierarchy of Protein Structure 8.4 Folding Thermodynamics, Haemoglobin Cooperativity & Denaturation 8.5 Catalytic Mechanisms, Enzyme Classification & Michaelis-Menten Kinetics 8.6 Enzyme Inhibition Modes & Allosteric Cooperativity

9 Biochemistry: Cellular Metabolism & Bioenergetics

9.1 Glycolysis: The Ten Steps, Regulation & Anaerobic Fermentation 9.2 Gluconeogenesis Bypass Enzymes & the Pentose Phosphate Pathway 9.3 The Pyruvate Dehydrogenase Complex & the Citric Acid (Krebs) Cycle 9.4 Mitochondrial Architecture & the Respiratory Complexes 9.5 Chemiosmotic Coupling, ATP Synthase, NADH Shuttles & Uncouplers 9.6 Fatty Acid Beta-Oxidation, Ketogenesis & Glycogen Dynamics

10 Molecular Biology: Nucleic Acids & Genetic Technologies

10.1 Nucleic Acid Chemistry, the Double Helix & Chromatin Organisation 10.2 DNA Replication: Replisome Enzymology & Fork Dynamics 10.3 DNA Damage & Cellular Repair Pathways 10.4 The Central Dogma, Strand Nomenclature & Transcription Machinery 10.5 Post-Transcriptional Processing of Eukaryotic Pre-mRNA 10.6 Regulation of Gene Expression: Operons, Enhancers & Epigenetics 10.7 The Genetic Code, Wobble & Mutation Taxonomy 10.8 tRNA Charging & the Stages of Ribosomal Translation 10.9 Translation Inhibitors & Post-Translational Processing 10.10 Restriction Enzymes, Cloning Vectors, cDNA Libraries & PCR 10.11 Blotting, Sequencing, Microarrays & CRISPR-Cas9

11 Cellular Biology & Microbiology

11.1 Eukaryotic Organelles, Membrane Transport & Cytoskeletal Dynamics 11.2 The Eukaryotic Cell Cycle, Mitosis, Checkpoints & Apoptosis 11.3 Cell Theory, Bacterial Morphology, Genetics & Sub-Viral Agents

12 Genetics, Evolution & Embryology

12.1 Mendel's Laws & the Cytology of Meiosis 12.2 Genetic Crosses, Non-Mendelian Inheritance, Linkage & Pedigree Analysis 12.3 The Hardy-Weinberg Principle, Assumptions & Clinical Calculations 12.4 Mechanisms of Evolution, Speciation & Macroevolutionary Patterns 12.5 Gametogenesis, Fertilisation, Cleavage & Implantation 12.6 Gastrulation, Germ Layer Derivatives, Stem Cell Potency & Neurulation

13 Human Physiology: Control & Transport Systems

13.1 Neuronal Anatomy, the Resting Potential & the Action Potential 13.2 Conduction Velocity, Synaptic Transmission & Postsynaptic Summation 13.3 Neurotransmitter Systems, CNS/PNS Organisation & Reflex Arcs 13.4 Hormone Classification & the Hypothalamus-Pituitary Axis 13.5 Negative Feedback Architecture, Endocrine Glands & Calcium Homeostasis 13.6 Cardiac Anatomy, Electrophysiology, the Cardiac Cycle & Cardiac Output 13.7 Vascular Hemodynamics, Starling Forces, Blood Components & Hemostasis 13.8 Respiratory Anatomy, Ventilation Mechanics & Pulmonary Surfactant 13.9 Spirometry, Dead Space, Gas Exchange & Haemoglobin Allostery 13.10 Carbon Dioxide Transport, the Chloride Shift & Acid-Base Control of Breathing

14 Human Physiology: Maintenance, Defense & Locomotion

14.1 Renal Anatomy, Glomerular Ultrafiltration & Tubular Transport 14.2 The Countercurrent Multiplier & Endocrine Regulation of Renal Function 14.3 GI Architecture, the Enteric Nervous System & Gastric Secretion 14.4 Pancreatic and Biliary Digestion & Intestinal Nutrient Absorption 14.5 Hepatic Processing, GI Endocrine Regulators & the Colon 14.6 Innate Immunity: Barriers, Complement & Cellular Effectors 14.7 Adaptive Humoral Immunity: B Cells & Immunoglobulins 14.8 Adaptive Cellular Immunity: T Cells, Thymic Selection & MHC Presentation 14.9 Muscle Types, Sarcomere Anatomy & Excitation-Contraction Coupling 14.10 Bone Architecture, Remodelling & the Integumentary System

15 CARS: Passage Analysis & Argument Mapping

15.1 CARS Architecture, Passage Genres (Humanities vs Social Sciences) & Mindset 15.2 Active Reading, Author's Central Thesis & Tone Analysis 15.3 Rhetorical Structure, Claim-Evidence Linkages & Argument Mapping

16 CARS: Question Types & Reasoning Strategies

16.1 Skill 1 Demands, Question Stems, Detail Retrieval & Paraphrase Recognition 16.2 Inferential Meaning, Distractor Taxonomy & a Worked Skill 1 Passage 16.3 Skill 2 Architecture, Question Stems, Unstated Assumptions & Evidence Strength 16.4 Rhetorical Mechanisms, Logical Fallacies & a Worked Skill 2 Passage 16.5 Skill 3 Architecture, Question Stems, Application & Analogy Mapping 16.6 Incorporating New Information, Calibrating Evidentiary Impact & a Worked Skill 3 Passage

17 Sensory Processing, Perception & Cognition

17.1 Sensation versus Perception & Sensory Receptor Classification 17.2 Psychophysical Thresholds, Weber's Law, Adaptation & Signal Detection Theory 17.3 Vision: Ocular Anatomy, Phototransduction & Central Visual Pathways 17.4 Audition & the Vestibular System 17.5 Somatosensation, Pain & Chemoreception 17.6 Models of Attention & Working Memory Architecture 17.7 Long-Term Memory Taxonomy, Encoding, Storage & Retrieval 17.8 Forgetting, Interference, Memory Distortion & Long-Term Potentiation 17.9 Problem Solving, Heuristics, Cognitive Biases & Language 17.10 Sleep Architecture, Circadian Neurobiology, Sleep Disorders & Psychoactive Drugs

18 Emotion, Stress, Motivation & Personality

18.1 Components of Emotion & Classical Theories of Emotion 18.2 The Limbic Circuit, Stress Appraisal & Selye's General Adaptation Syndrome 18.3 Intrinsic and Extrinsic Motivation, Drive-Reduction, Arousal & Incentive Theories 18.4 Cognitive and Humanistic Need Models & the Neuroendocrine Control of Hunger and Sex 18.5 The Psychoanalytic Perspective & Neo-Freudian Revisions 18.6 Humanistic, Trait & Social-Cognitive Perspectives on Personality 18.7 Biopsychosocial Etiology, Schizophrenia, Mood & Anxiety Disorders 18.8 Somatic, Dissociative, Personality & Neurodegenerative Disorders

19 Learning, Social Behavior & Identity

19.1 Non-Associative Learning & Classical Conditioning 19.2 Operant Conditioning, Reinforcement Schedules & Observational Learning 19.3 Self-Concept & Lifespan Developmental Theories 19.4 Kohlberg's Moral Development & Sociocultural Frameworks 19.5 Social Influence: Conformity, Obedience, Group Dynamics & Prosocial Behavior 19.6 Social Cognition, Attribution Theory, Prejudices, Stereotypes & Discrimination

20 Sociology, Demographics & Healthcare Disparities

20.1 Macro versus Micro Paradigms, Structural Functionalism & Conflict Theory 20.2 Symbolic Interactionism, Social Constructionism & Modern Paradigms 20.3 Major Social Institutions: Structure, Function & Dysfunction 20.4 Demographics, Population Pyramids, the Demographic Transition & Globalisation 20.5 Systems of Stratification, Socioeconomic Status & Social Mobility 20.6 Poverty, Spatial Inequality, the Socioeconomic Gradient & Health Inequities

18.7 Biopsychosocial Etiology, Schizophrenia, Mood & Anxiety Disorders

Key Takeaways Explain This Topic AI

The DSM-5 establishes categorical criteria based on symptom clusters and functional impairment without prescribing etiology, analyzed through the biopsychosocial framework and the diathesis-stress model.

Schizophrenia is characterized by positive symptoms (hallucinations, delusions, thought disorganization) linked to mesolimbic hyperdopaminergic signaling and negative symptoms (avolition, flat affect) linked to mesocortical hypodopaminergic activity, alongside cerebral ventriculomegaly.

Major Depressive Disorder requires five of nine SIGECAPS symptoms including depressed mood or anhedonia driven by monoaminergic dysregulation, whereas Bipolar I necessitates at least one manic episode (DIG FAST criteria) and Bipolar II requires hypomania plus depression.

Last updated: September 2026

18.7 Biopsychosocial Etiology, Schizophrenia, Mood & Anxiety Disorders

Note

Diagnostic Foundations on the MCAT : The American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) classifies mental conditions categorically based on observable symptom clusters, symptom duration, and clinically significant distress or functional impairment. The DSM-5 is explicitly atheoretical regarding etiology. On the MCAT, psychological disorders must be evaluated through the biopsychosocial framework and the diathesis-stress model .

Etiological Models: Biopsychosocial & Diathesis-Stress

The Biopsychosocial Model : Posits that mental illness arises from the complex, non-linear interaction of three interdependent domains:

Biological : Genetic vulnerabilities, monoamine imbalances, structural neuroanatomy, and neuroendocrine dysregulation.

Psychological : Maladaptive cognitive schemas, appraisal styles, perceived self-efficacy, and learned behaviors.

Sociocultural : Socioeconomic adversity, systemic prejudice, interpersonal trauma, cultural expectations, and social support.

The Diathesis-Stress Model : Asserts that psychological disorders manifest when an underlying constitutional vulnerability ( diathesis )—which may be genetic (e.g., 5-HTTLPR short allele), neurodevelopmental, or cognitive—is triggered by an environmental or psychological stressor . An individual with a high genetic diathesis requires only modest environmental stress to develop a disorder, whereas an individual with a low diathesis requires severe, chronic stress.

Schizophrenia & Psychotic Disorders

Schizophrenia is a severe neurodevelopmental psychotic disorder affecting approximately 1% of the global population. Diagnosis requires continuous signs of disturbance for at least 6 months , including at least 1 month of active-phase symptoms with at least two of the following five criteria (and at least one must be 1, 2, or 3):

  • Delusions
  • Hallucinations
  • Disorganized speech
  • Grossly disorganized or catatonic behavior
  • Negative symptoms
  • Symptom Typology

Positive Symptoms (Pathological Excesses) : Behaviors, perceptions, or thoughts added to normal functioning:

Delusions : Fixed, false beliefs resistant to contradictory evidence. Includes delusions of persecution (believing one is targeted by enemies), reference (believing mundane environmental events have personal significance), grandeur (believing one possesses divine powers), and control (thought insertion, thought broadcasting).

Hallucinations : Sensory perceptions occurring without an external physical stimulus. Auditory hallucinations (hearing derogatory or commanding voices) are by far the most prevalent.

Disorganized Speech & Thought : Derailment (loose associations), tangentiality, and neologisms (invented words), culminating in extreme cases in "word salad".

Disorganized / Catatonic Behavior : Bizarre posturing, purposeless motor agitation, or waxy flexibility (maintaining limbs in positions placed by an examiner).

Negative Symptoms (Pathological Deficits) : Normal functions subtracted from healthy mental life:

Affective Flattening (Blunted Affect) : Reduced range and intensity of emotional expression.

Avolition : Profound lack of motivation and inability to initiate or persist in goal-directed activities.

Alogia : Poverty of speech in fluency and productivity.

Anhedonia : Inability to experience pleasure from previously rewarding activities.

Asociality : Profound lack of interest in social interactions.

Neurobiological Pathophysiology

The Dual Dopamine Hypothesis :

Mesolimbic Hyperactivity : Excessive dopaminergic transmission from the ventral tegmental area (VTA) to the nucleus accumbens mediates positive symptoms . First-generation (typical) neuroleptics (e.g., haloperidol) antagonize D2 receptors, alleviating positive symptoms but carrying high risk of extrapyramidal motor side effects and tardive dyskinesia.

Mesocortical Hypoactivity : Deficient dopaminergic transmission from the VTA to the prefrontal cortex mediates negative and cognitive symptoms . Second-generation (atypical) antipsychotics (e.g., risperidone, clozapine) antagonize serotonin 5-HT2A and D2 receptors to modulate both circuits.

Neuroanatomical Hallmarks : Marked enlargement of the lateral and third cerebral ventricles ( ventriculomegaly ), reflecting widespread loss of cortical gray matter in the prefrontal cortex and temporal lobes.

  • Mood Disorders: Depressive & Bipolar Disorders
  • 1. Major Depressive Disorder (MDD)

Requires at least two weeks of persistent depressed mood or loss of interest/pleasure ( anhedonia ), accompanied by at least five of the nine symptoms summarized by the clinical mnemonic SIGECAPS :

  • S leep disturbances (insomnia or hypersomnia)
  • I nterest loss (pervasive anhedonia; mandatory core symptom)
  • G uilt or feelings of worthlessness (inappropriate or delusional)
  • E nergy deficiency (chronic fatigue, psychomotor anergia)
  • C oncentration impairment (indecisiveness, cognitive slowness)
  • A ppetite or weight alterations (significant change of ≥ 5 % \ge 5\% ≥ 5% in a month)
  • P sychomotor agitation or retardation (observable by others)
  • S uicidal ideation, intent, or recurrent thoughts of death

Neurobiology : Grounded in the Monoamine Hypothesis —deficiencies in synaptic transmission of serotonin (5-HT) , norepinephrine (NE) , and dopamine (DA) in limbic-cortical networks. Supported by the efficacy of Selective Serotonin Reuptake Inhibitors (SSRIs). Patients frequently exhibit sustained HPA axis hyperactivity (hypercortisolemia) and hippocampal volumetric reductions.

2. Bipolar Disorders & The Manic Episode

Bipolar I Disorder : Requires the occurrence of at least one full manic episode . Major depressive episodes are common but not required for diagnosis.

Bipolar II Disorder : Requires at least one hypomanic episode AND at least one major depressive episode . A full manic episode precludes a Bipolar II diagnosis (immediately converting it to Bipolar I).

Cyclothymic Disorder : At least 2 years of alternating hypomanic symptoms and depressive symptoms that do not meet full criteria for an episode.

Diagnostic Criteria for Mania : At least one week of abnormally elevated, expansive, or irritable mood with increased goal-directed energy, presenting with at least three (or four if mood is irritable) symptoms from the mnemonic DIG FAST :

  • D istractibility (attention easily drawn to trivial external stimuli)
  • I ndiscretion (hedonistic, high-risk activities: unrestrained spending, reckless driving)
  • G randiosity (inflated self-esteem, delusions of omnipotence)
  • F light of ideas (subjective experience that thoughts are racing)
  • A ctivity increase (hyperactivity, psychomotor agitation)
  • S leep deficit (decreased need for sleep, feeling rested after only 2–3 hours)
  • T alkativeness (pressured, rapid, loud, uninterrupted speech)

Hypomania vs. Mania : Hypomania lasts at least 4 consecutive days, does not cause marked social or occupational impairment, does not involve psychotic symptoms, and does not require psychiatric hospitalization.

Anxiety Disorders, OCD & Trauma-Related Conditions

Generalized Anxiety Disorder (GAD) : Pervasive, excessive, uncontrollable worry regarding multiple daily domains for at least 6 months , accompanied by motor tension, restlessness, fatigue, and sleep disturbances.

Panic Disorder : Characterized by recurrent, unexpected panic attacks —abrupt surges of intense autonomic terror accompanied by palpitations, dyspnea, chest pain, tremors, and fear of impending death or losing control. Requires at least 1 month of persistent concern regarding future attacks or maladaptive behavioral modifications (frequently progressing to agoraphobia —fear of open, enclosed, or crowded spaces from which escape might be difficult).

Phobias : Specific phobias (animals, natural environments, blood-injection-injury) vs. Social Anxiety Disorder (severe, persistent fear of social or performance situations involving scrutiny or humiliation).

Obsessive-Compulsive Disorder (OCD) :

Obsessions : Recurrent, persistent, intrusive thoughts, urges, or images that cause marked anxiety. Crucially, obsessions are ego-dystonic (the patient recognizes them as irrational, intrusive, and contrary to their core self).

Compulsions : Repetitive behaviors (hand-washing, checking, ordering) or mental acts (counting, silent prayer) that the individual feels driven to perform to neutralize the anxiety generated by obsessions.

Neurobiology : Hyperactivity within the cortico-striato-thalamo-cortical (CSTC) circuit , linking the orbitofrontal cortex, anterior cingulate, and caudate nucleus.

Post-Traumatic Stress Disorder (PTSD) : Emerges following direct exposure to actual or threatened death, serious injury, or sexual violence. Symptoms must persist for greater than 1 month (distinguishing it from Acute Stress Disorder , which spans 3 days to 1 month) across four symptom clusters: (1) Intrusion (nightmares, flashbacks), (2) Avoidance (evading trauma reminders), (3) Negative alterations in mood/cognition (dissociative amnesia, blame, anhedonia), and (4) Hyperarousal (hypervigilance, exaggerated startle reflex).

Schizophrenia: Symptom Domains and Duration Criteria

Positive and negative symptoms map to opposite dopaminergic abnormalities in different tracts, which is why one domain responds far better to antipsychotics than the other.

  • Symptom domain Representative features Dopaminergic correlate Response to typical antipsychotics
  • Positive Hallucinations, delusions, disorganised speech and behaviour Mesolimbic hyperactivity Good
  • Negative Flat affect, avolition, alogia, anhedonia, asociality Mesocortical hypoactivity Poor
  • Cognitive Impaired working memory and executive function Prefrontal dysfunction Poor

Duration separates the psychotic disorders: symptoms lasting less than one month indicate brief psychotic disorder, one to six months schizophreniform disorder, and six months or more schizophrenia.