Difficulty: Introductory | Prerequisites: None, though familiarity with basic biology (cells, organs, body systems) will help.
Health psychology sits at the intersection of psychology and medicine, exploring how thoughts, feelings, behaviours, and social conditions influence physical health and illness. These two chapters lay the groundwork: Chapter 1 introduces the field, its models, and its research methods, while Chapter 2 surveys the body systems you will reference throughout the course. If you have been away from the material for a few weeks, start here. Everything that follows in Chapters 3 and 4 (health behaviours, behaviour change models, health promotion) builds on these foundations.
Health psychology studies how psychological, social, and biological factors interact to influence health and illness, replacing the old biomedical model with the biopsychosocial model. The field exists because chronic diseases have overtaken infectious ones as leading causes of death, the population is ageing, and healthcare costs keep climbing. Chapter 2 maps the body systems (nervous, endocrine, cardiovascular, immune, and others) that health psychologists need to understand when studying how stress, behaviour, and social conditions affect physical health.
Health
A complete state of physical, mental, and social well-being, not merely the absence of disease or infirmity. In simple terms, being healthy means more than just "not being sick."
Wellness
The optimum state of health, achieved through balance among physical, mental, and social well-being. Think of it as health at its best, not just the baseline.
Biomedical model
The view that illness can be fully explained by aberrant somatic bodily processes such as biochemical imbalances or neurophysiology abnormalities. In simple terms, this model says disease is purely a biological malfunction.
Biopsychosocial model
A framework holding that biological (cells, genetics), psychological (thoughts, emotions, behaviours), and social (culture, SES, relationships) factors all interact to influence health and illness. Think of it as the "whole person" approach to understanding disease.
Etiology
The study of the origins or causes of a disease or condition.
Humoral theory of illness
The Ancient Greek idea that disease resulted from an imbalance among four circulating body fluids: blood, black bile, yellow bile, and phlegm.
Randomized clinical trial (RCT)
A study conducted to evaluate the effectiveness of treatments or interventions over time, with participants randomly assigned to conditions.
Correlational study
A research design that measures whether changes in one variable are related to changes in another, without establishing causation.
Meta-analysis
A research method that statistically combines results of multiple studies to determine the average relationship between variables across those studies.
Prospective research
Research that looks forward in time to understand risk factors related to health or illness.
Retrospective research
Research that looks backward in time to reconstruct the conditions that led to a current situation.
Evidence-based medicine
The principle that medical interventions go through rigorous testing and evaluation of their benefits before they become the standard of care.
Central nervous system (CNS)
The brain and spinal cord, carrying voluntary nerve impulses to skeletal muscles and involuntary impulses to muscles and glands.
Peripheral nervous system (PNS)
All nerves outside the brain and spinal cord, divided into the somatic (voluntary movement) and autonomic (involuntary organ control) divisions.
Sympathetic nervous system
The branch of the autonomic nervous system that mobilises the body for action: fight or flight.
Parasympathetic nervous system
The branch that maintains and restores equilibrium: rest and digest.
Neurotransmitters
Chemicals that transmit signals across synapses throughout the nervous system. Some encourage signal sending, some decrease uptake, and some broadcast many signals at once.
Catecholamines
Epinephrine and norepinephrine, secreted by the adrenal medulla during the stress response as part of sympathetic activation.
Natural immunity
Immunity acquired by surviving a disease or receiving it in utero or during breastfeeding, involving anatomical barriers, phagocytosis, antimicrobial substances, and inflammatory responses.
Artificial immunity
Immunity acquired through vaccination.
Social determinants of health
Conditions in which people are born, grow, live, work, and age that affect health outcomes, including education access, healthcare access, neighbourhood environment, social context, and economic stability.
How people stay healthy
Why they become ill
How they respond when they get ill
The role of culture and policy in health outcomes
Prehistory: Mind and body were intertwined. Disease was attributed to evil spirits entering the body; exorcism was the cure.
Ancient Greeks: Developed the humoral theory. Illness arose when the four humors went out of balance: blood (passionate temperament), black bile (sadness), yellow bile (angry disposition), and phlegm (laid-back approach).
Middle Ages: Disease was viewed as God's punishment.
The biomedical model explains illness through aberrant somatic bodily processes: biochemical imbalances, neurophysiology abnormalities, cell disease. It has four core weaknesses:
Reduces illness to lower-level processes (cell disease, chemical imbalances)
Fails to recognise the power of social and psychological processes
Emphasises illness rather than behaviours that enhance health
Cannot address the complex puzzles providers actually face
Freud's insight that unconscious conflicts can produce physical disturbances helped shift the field away from a purely biomedical view.
Advantages: Holds that macrolevel (social) and microlevel (cells, genetics) processes continually interact to influence health and illness. Emphasises both health and illness, not just disease.
In practice: The three factors are rarely weighted equally. Biology typically receives the most attention.
Clinical implications: Understanding the interacting role of biological, psychological, and social factors informs diagnosis. Emphasis on the patient-provider relationship improves patient use of services, treatment efficacy, and how quickly illness is resolved.
Chronic illness is dominant. Chronic, lifestyle-related illnesses (heart disease, respiratory disease, cancer) are now the main contributors to disability and death. Infectious diseases are no longer the primary killers in industrialised countries.
The population is ageing. By 2030, those aged 80 and older will outnumber infants. Future providers will primarily care for older adults.
Technology creates new psychological questions. Genetic testing for cancer risk, treatments that prolong life but may compromise its quality, decisions about life-saving measures: all require psychological support.
Healthcare spending is high, outcomes are middling. Large disparities in healthcare quality and access persist. Health psychologists can help with prevention, modify risky behaviours, and design user-friendly healthcare systems.
Increased acceptance of health psychologists. They now help manage pain, modify health habits (e.g. smoking), control treatment side effects, and prepare patients for unpleasant procedures.
The research cycle runs: Reality → Theory → Hypotheses → Data → Applications (recommendations for supporting motivation and behaviour in applied settings).
Experiments: Two or more conditions are created, people are assigned randomly, reactions are measured.
Advantages: can determine causation, higher control, rule out bias
Disadvantages: some cannot be done for ethical reasons, rigid (reduced generalisability), cannot test all variables, resource-heavy
Randomized clinical trials (RCTs): Evaluate effectiveness of treatments or interventions over time.
Evidence-based medicine: Interventions are rigorously tested before becoming standard of care.
Correlational studies: Measure whether changes in one variable relate to changes in another.
Advantages: more adaptable, cheaper
Disadvantages: cannot determine direction of causality
Longitudinal studies: Same people observed at multiple points in time.
Prospective vs. retrospective: Prospective looks forward (risk factors); retrospective looks backward (reconstructing conditions).
Quantitative vs. qualitative: Quantitative uses numerical data; qualitative uses open-ended data in words.
Meta-analysis: Statistically combines results across multiple studies to determine effect size. Potential problems include personal bias influencing which studies are included, and publication bias (only "good" or significant results get reported).
fMRI is effective at identifying brain activity trends across groups, but it cannot consistently measure activity within a single person over time. Across 56 tests, brain activation patterns were inconsistent across repeated tests. This matters for health psychology because it shows that psychological and social factors play a role in mental health and brain behaviour, not just biological functional processes.
Central Nervous System (CNS) – Brain and Spinal Cord
Carries voluntary nerve impulses to skeletal muscles and skin, and involuntary impulses to muscles and glands.
Peripheral Nervous System (PNS)
Somatic NS: controls voluntary movement
Autonomic NS: controls organs that operate involuntarily
Sympathetic: mobilises the body for action (fight or flight)
Parasympathetic: maintains and restores equilibrium (rest and digest)
Major Brain Structures
Hindbrain:
Pons: links hindbrain and midbrain, helps with respiration, includes nuclei involved in motor function, sleep, taste, and learning
Cerebellum: coordinates voluntary muscle movement, balance, muscle tone (roughly 10% of the brain but over half its nerve cells)
Medulla: regulates heart rate, blood pressure, respiration, functions that are outside conscious control
Midbrain: Pathway for sensory and motor impulses, mostly auditory and visual processing
Forebrain:
Cerebral cortex: intelligence, memory, personality. Includes frontal, parietal, temporal, and occipital lobes.
Thalamus: sensory information arrives here first
Hypothalamus: mediator of cerebral cortex processing and organ impact, maintains steady state
Chemicals that transmit signals through synapses throughout the nervous system. Some encourage signal sending, some decrease uptake, and some send many signals at once.
Adrenal gland activity in stress response:
Adrenal glands contain the adrenal medulla and adrenal cortex
The adrenal medulla secretes epinephrine and norepinephrine (sympathetic activation, fight or flight)
Catecholamines (epinephrine, norepinephrine), sympathetic stimulation, and corticosteroids are all responses to stress
Type I vs. Type II Diabetes
Type I: arises in late childhood or early adolescence, partly genetic, autoimmune. Destroys islets of Langerhans in the pancreas, compromising the ability to produce insulin.
Type II: more common, primarily in adulthood, resulting from environmental and social determinants. Insulin is produced but either not enough of it or the body is not sensitive to it.
The heart, blood vessels, and blood form the body's transport system. Blood carries oxygen, nutrients, waste, and hormones. The cycle of contraction and relaxation pumps blood through the heart.
The concept of "lifestyle factors" has limitations:
Assumes equitable access to resources
Ignores barriers people face
Ignores the interconnectedness of challenges
Five categories: education access and quality, healthcare access and quality, neighbourhood and built environment, social and community context, economic stability.
Inspiration brings air through the trachea to the lungs. Expiration exhales CO2. The respiratory centre in the medulla controls breathing.
Gastric secretions in the stomach help digest food. Enzymes in the small intestine turn proteins into amino acids. The large intestine stores food residue and helps reabsorb water.
Dr. Weaver's warning: a connection exists, but there is very little evidence for the strong claims often made about it.
Referring to "male" and "female" reproductive systems is inaccurate. Testicular and ovarian system is more precise. External reproductive anatomy can differ from internal anatomy. Physiological sex determination is immediate at birth, after which sociological gender ideas are immediately applied.
Natural immunity is acquired by surviving disease or receiving immunity in utero or during breastfeeding. It operates through four mechanisms:
Phagocytosis: phagocytes (white blood cells) ingest a microbe to eliminate it
Anatomical barriers: skin and mucus membranes prevent passage of microbes from one section of the body to another
Antimicrobial substances: chemicals produced by the body that kill invading microorganisms (e.g. interferon, hydrochloric acid)
Inflammatory response: local reaction to infection (e.g. histamine release)
Artificial immunity is acquired through vaccination.
Genetic counselling involves genetic testing for risk and discussion about how to proceed. This is not genetic engineering.
Students often think the biomedical model is simply "wrong." It is limited, not useless. It still explains many disease processes, but it cannot account for the full picture of health and illness on its own.
Students often confuse correlation with causation when discussing correlational studies. A correlational study can show that two variables move together, but it cannot tell you which one causes the other, or whether a third variable drives both.
Students often assume the biopsychosocial model weights all three factors equally in practice. In reality, biology tends to receive the most attention.
Students sometimes mix up the sympathetic and parasympathetic nervous systems. A quick mnemonic: sympathetic = stress (fight or flight); parasympathetic = peace (rest and digest).
Know the four focuses of health psychologists: health promotion and maintenance, prevention and treatment of illness, etiology and correlates, healthcare system improvement.
Be able to explain why the biomedical model is ill-suited to understanding illness, using at least three of the four reasons.
Understand the biopsychosocial model's advantages and its clinical implications (patient-provider relationship, patient use of services, treatment efficacy, speed of illness resolution).
Know the advantages and disadvantages of experiments, correlational studies, and meta-analyses.
Be able to distinguish prospective from retrospective research.
For body systems, focus on application: what each system does and how it connects to health psychology, rather than memorising every disease.
Know the Duke fMRI finding and why it supports the biopsychosocial perspective.
Understand the difference between Type I and Type II diabetes (onset, mechanism, causes).
Know all four mechanisms of natural immunity: phagocytosis, anatomical barriers, antimicrobial substances, inflammatory response.
Understand what social determinants of health are and why "lifestyle factors" as a concept has limitations.
True or False: The biomedical model accounts for social and psychological influences on illness.
Fill in the blank: The branch of the autonomic nervous system responsible for "rest and digest" is the _______ nervous system.
True or False: A correlational study can establish causation.
Fill in the blank: In the biopsychosocial model, the three interacting factors are biological, _______, and social.
True or False: Type II diabetes is an autoimmune disorder that typically arises in childhood.
Answers: 1. False 2. Parasympathetic 3. False 4. Psychological 5. False (that describes Type I; Type II arises primarily in adulthood from environmental and social determinants)
Q: What are the four focuses of health psychologists?
A: Health promotion and maintenance, prevention and treatment of illness, etiology and correlates of health/illness/dysfunction, and improvement of the healthcare system and formulation of health policy.
Q: Name three reasons the biomedical model is ill-suited to understanding illness.
A: It reduces illness to lower-level processes, ignores social and psychological influences, emphasises illness rather than health-promoting behaviours, and cannot address complex clinical puzzles.
Q: What is the key advantage of an experiment over a correlational study?
A: Experiments can determine causation through random assignment and controlled conditions. Correlational studies can only show that variables are related, not which causes which.
Q: A researcher follows a group of healthy college students for 20 years to see who develops heart disease. What type of study is this?
A: A prospective, longitudinal study.
Q: What is the main limitation of meta-analysis?
A: Personal bias or expectation may influence which studies are selected, and publication bias means only significant or supportive results may be reported.
Q: Describe the function of the hypothalamus.
A: The hypothalamus mediates cerebral cortex processing and organ impact, and works to maintain a steady state (homeostasis) in the body.
Q: Distinguish between natural and artificial immunity.
A: Natural immunity is acquired by surviving a disease or receiving immunity in utero or during breastfeeding, using mechanisms like phagocytosis and inflammatory responses. Artificial immunity is acquired through vaccination.
Q: Why did the Duke fMRI study matter for health psychology?
A: It showed that fMRI brain activation patterns are inconsistent within the same person across repeated tests, meaning fMRI is unreliable for predicting individual mental health or behaviour. This supports the view that psychological and social factors, not just biological ones, play a role in mental health.
The biopsychosocial model introduced here is the lens through which all later material is viewed: Chapter 3's health behaviour models (Health Belief Model, Theory of Planned Behaviour, Transtheoretical Model) all assume that psychology and social context matter alongside biology. The body systems from Chapter 2, particularly the nervous system, endocrine system, and immune system, come back heavily when you study stress (Chapter 6) and coping. The social determinants of health concept connects directly to Chapter 4's discussion of barriers to screenings, exercise, and healthy diet.
Health psychology, biopsychosocial model, biomedical model, mind-body relationship, humoral theory, chronic illness, social determinants of health, CNS, PNS, sympathetic nervous system, parasympathetic nervous system, fight or flight, rest and digest, neurotransmitters, catecholamines, adrenal glands, epinephrine, norepinephrine, Type I diabetes, Type II diabetes, cardiovascular system, immune system, phagocytosis, natural immunity, artificial immunity, vaccination, fMRI reliability, experiment vs. correlation, meta-analysis, RCT, evidence-based medicine, prospective research, retrospective research, longitudinal study, qualitative vs. quantitative, genetic counselling, PSY 320, Michigan State University, health and wellness definition