AP Syllabus focus:
‘The biopsychosocial and diathesis-stress models explain disorders as the result of interacting biological, psychological, sociocultural, and stress-related factors.’
Interaction models of psychopathology explain mental disorders as the product of multiple, mutually influencing causes. Instead of searching for one “root” explanation, these models integrate risk and protection across body, mind, and environment.
Core idea: disorders emerge from interacting influences
Mental disorders are more likely when risk factors cluster and reinforce one another over time. Interaction models emphasize that:
Causes can be bidirectional (e.g., symptoms change environments, which then worsen symptoms).
Different combinations of factors can lead to similar outcomes (multiple pathways).
The same risk factor can have different effects depending on context (moderation), timing, and protective supports.
The biopsychosocial model
The biopsychosocial model explains psychopathology using coordinated biological, psychological, and sociocultural levels of analysis.
Venn diagram of the biopsychosocial model showing how Biological, Psychological, and Social/Environmental factors overlap to influence mental health. The intersections illustrate how disorders are often best explained by combinations of influences (e.g., stress physiology interacting with coping skills and social context), rather than by a single cause. Source
Biopsychosocial model: A framework proposing that mental disorders result from interacting biological, psychological, and sociocultural factors.
A key implication is that assessment and treatment often require looking across levels, because factors can combine in additive and interactive ways.
Biological contributors (bio)
These are bodily and genetic influences that can increase vulnerability or shape symptom expression, such as:
Genetic risk and inherited temperament
Brain structure/function differences in relevant circuits
Neurotransmitter and hormone processes linked to arousal and mood
Sleep, inflammation, and other health conditions that affect emotion and cognition
Biological factors rarely act alone; they can increase sensitivity to psychological stressors or reduce flexibility in coping.
Psychological contributors (psycho)
These are mental and behavioral processes that influence how experiences are interpreted and managed:
Cognitive appraisals (how threatening or controllable a situation feels)
Emotion regulation skills (or difficulties)
Learning history that shapes avoidance, safety behaviors, and reinforcement patterns
Self-concept and expectations that bias attention and memory toward threat or failure
Psychological processes can also feed back into biology (e.g., chronic worry elevating physiological arousal).
Sociocultural contributors (social/cultural)
These are environmental and cultural conditions that shape exposure to stress and access to support:
Family dynamics, attachment security, and parenting practices
Peer relationships, isolation, and social support
Socioeconomic stress, discrimination, and barriers to care
Cultural norms affecting symptom expression, coping, and help-seeking
Sociocultural factors can create chronic stress contexts, altering both coping habits and physiological stress responses.
The diathesis-stress model
The diathesis-stress model explains disorders as developing when a predisposition is activated by stressors.
Diathesis-stress model: A framework proposing that a diathesis (vulnerability) interacts with stress to produce psychopathology.
This model highlights why not everyone exposed to the same stressor develops a disorder: vulnerability levels and protective resources differ.
Diathesis: vulnerability does not equal destiny
A diathesis can be biological, psychological, or sociocultural in origin.
Diathesis: A pre-existing vulnerability (genetic, physiological, cognitive, or environmental) that increases the likelihood of developing a disorder under stress.
Diatheses may remain latent until triggered, and they can be reduced or compensated for by skill-building, support, and stable environments.
Stress: triggers, load, and timing
In this model, stress-related factors include:
Acute stressors (sudden events) that can precipitate symptom onset
Chronic stress that gradually erodes coping capacity
Developmental timing, where stress at sensitive periods may have stronger effects
Cumulative burden, where multiple smaller stressors combine into significant risk
Protective factors and resilience within interaction models
Interaction models also account for protective factors that buffer risk:
Supportive relationships and belonging
Effective coping skills and flexible problem-solving
Access to resources (safe housing, healthcare, stable routines)
Meaning-making and adaptive beliefs that reduce helplessness
Protective factors can interrupt feedback loops (e.g., stress → symptoms → social withdrawal → more stress) and lower the chance that vulnerability becomes disorder.
FAQ
Additive risk means each factor independently increases likelihood.
Interactive risk means the effect of one factor depends on another (e.g., a vulnerability matters far more under high stress).
A feedback loop is a self-reinforcing cycle where symptoms change behaviour or environments, which then worsen symptoms.
Examples include withdrawal reducing support, or poor sleep increasing anxiety, which further disrupts sleep.
Yes. A diathesis can include chronic environmental vulnerability, such as long-term exposure to conflict, limited access to resources, or persistent discrimination.
These can lower baseline coping capacity and increase sensitivity to stress.
Buffering means protective factors reduce how strongly stress affects functioning.
This can occur through:
lowering perceived threat
increasing coping options
providing practical help that reduces stress exposure
No. They allow multiple pathways to similar outcomes.
Two people may show similar symptoms for different mixes of vulnerability, stress exposure, and protective factors, which can also change across the lifespan.
Practice Questions
Outline the diathesis-stress model of psychopathology. (2 marks)
1 mark: States that a disorder results from an interaction between a vulnerability/diathesis and stress.
1 mark: Clarifies that stress may trigger/activate the diathesis and that either factor alone may be insufficient.
Explain how the biopsychosocial model accounts for the development of a psychological disorder by referring to biological, psychological, sociocultural, and stress-related factors and how they can interact. (6 marks)
1 mark: Identifies a relevant biological factor (e.g., genetic vulnerability, neural/hormonal processes).
1 mark: Identifies a relevant psychological factor (e.g., maladaptive appraisals, emotion regulation, learned avoidance).
1 mark: Identifies a relevant sociocultural factor (e.g., low support, socioeconomic strain, discrimination).
1 mark: Includes stress-related factors (acute or chronic stressors) as part of the explanation.
1 mark: Describes interaction (e.g., stress activating vulnerability; factors amplifying one another).
1 mark: Notes bidirectionality/feedback loops or buffering by protective factors.
