This guide explains mental health as an ongoing interaction between a developing organism and its environment. It unpacks how prenatal biology, caregiving, relationships, social conditions, stress physiology and current circumstances may shape emotional regulation and behaviour. You will learn why symptoms such as anxiety, avoidance, emotional suppression, compulsive control, dissociation or hypervigilance may have once served a protective function: and why the same responses can become costly when the environment changes.
This is not an argument that every mental-health difficulty is caused by the environment, or that symptoms should simply be accepted. It is a more precise clinical question:
What has this organism been required to adapt to, and what is it still adapting to now?
1. Mental health is not created in isolation
Mental health is often described as though it resides entirely within the individual. A person develops anxiety, depression, trauma symptoms or compulsive behaviour, and treatment focuses on the person who carries the diagnosis.
There is value in identifying symptoms and providing effective treatment. However, an exclusively individual model can overlook the developmental conditions in which the nervous system, emotional architecture and behavioural strategies were formed.
A developmental-calibration model proposes that mental health is an emergent property of:
- Biological and genetic characteristics
- Prenatal conditions
- Caregiving and attachment relationships
- Family, school and workplace environments
- Social connection, belonging and exclusion
- Sleep, nutrition, movement and physical health
- Economic and structural conditions
- The person’s interpretation of current events
The causal pathway is recursive rather than one-directional:
- The environment shapes the developing organism.
- The organism responds to that environment.
- Those responses alter relationships and surroundings.
- The changed environment feeds back into the organism.
For example, a temperamentally reactive child may evoke different responses from caregivers. A withdrawn adolescent may receive fewer social invitations, which can deepen isolation. An anxious employee may seek repeated reassurance, unintentionally changing workplace interactions in ways that maintain anxiety.
The individual is neither simply the cause of the problem nor merely a passive recipient of circumstances. The person participates in a dynamic system.
2. Development begins before birth
Development does not begin at birth. Prenatal development occurs within a biological environment shaped by maternal physiology, placental function, nutrition, endocrine signalling, immune activity, oxygenation, infection, medication exposure and other factors.
Genes provide biological architecture and constraints, but genes do not operate in isolation. Development involves continuous interaction between genetic systems and environmental conditions. Cells communicate, regulatory pathways are activated or suppressed, and physiological systems adjust as the organism develops.
Research has associated prenatal stress exposure with later differences in stress regulation and cortisol responses. These findings are important, but they do not mean that prenatal stress determines a child’s mental health. Associations are influenced by many factors, including genetics, postnatal care, social support and later experiences.
“Developmental plasticity is the capacity of a single genotype to produce different phenotypes in response to environmental conditions.”
: Bateson et al. (2004), Nature ([academic reference](https://doi.org/10.1038/ nature03098))
Birth marks a major change in the form of environmental influence. The newborn enters a relational world where warmth, touch, feeding, predictability, caregiver responsiveness and social contact begin providing information about what to expect.
The infant is learning before it can describe what it has learned:
- Is distress followed by comfort?
- Is proximity safe?
- Are caregivers predictable?
- Does signalling lead to assistance, rejection or danger?
- Can the body rest, or must it remain alert?
These are not abstract psychological questions. They are regulatory problems that the developing nervous system must solve.
3. Calibration: development is adjustment, not simply growth
Calibration means that the nervous system adjusts its sensitivity, attention, arousal and behavioural responses according to the conditions it repeatedly encounters.
If danger is frequent, rapid threat detection may become useful. If caregivers are unreliable, heightened attachment signalling may increase the chance of maintaining proximity. If emotional expression leads to punishment, emotional suppression may reduce conflict. If unpredictability dominates daily life, compulsive control may create a temporary sense of order.
The following table illustrates how a response may begin as an understandable solution:
| Environmental condition | Possible calibration | Later cost when conditions change |
|---|---|---|
| Frequent conflict or threat | Hypervigilance and rapid scanning | Difficulty relaxing in safe settings |
| Unreliable caregiving | Reassurance-seeking or attachment anxiety | Fear of abandonment in stable relationships |
| Punishment for emotional expression | Suppression and emotional detachment | Difficulty identifying needs or connecting |
| Unpredictability and limited control | Checking, planning and compulsive control | Rigidity, exhaustion and reduced flexibility |
| Interpersonal danger with no escape | Dissociation or emotional numbing | Disconnection from memory, body or relationships |
| Repeated rejection or humiliation | Withdrawal and avoidance | Reduced opportunities for belonging and growth |
A response can therefore be historically adaptive and currently maladaptive.
This distinction is clinically important. The present-day cost of a behaviour does not tell us how that behaviour originated. A strategy that protected someone in one environment may restrict their life in another.
4. Mismatch: when an old solution meets a new ecology
Mismatch occurs when the nervous system continues applying a previously useful prediction to a new environment.
Consider someone who grew up around unpredictable anger. As a child, noticing subtle shifts in facial expression, voice or body posture may have helped them anticipate conflict. That sensitivity may have been intelligent and protective.
Twenty years later, the person may be living in a safe relationship or supportive workplace. Yet their nervous system may still interpret a neutral facial expression or delayed text message as an approaching threat.
The organism has moved, but the regulatory prediction has remained.
Developmental research refers to this as a form of phenotype–environment mismatch: a characteristic shaped in one environment becomes less suitable in another. The process is not conscious and does not imply personal weakness. It reflects the nervous system’s tendency to use prior experience to predict what is likely to happen next.
The Adaptive Calibration Model describes stress-response systems as both protective mechanisms and information-processing systems. They help coordinate responses to challenge, encode environmental information and regulate attention, learning, attachment and defensive behaviour.
A longitudinal study of 351 Dutch adolescent males found evidence for different physiological stress-response patterns associated with family and ecological conditions, life stress and behavioural outcomes. The authors also emphasised that the model is complex and requires further empirical testing (Ellis, Oldehinkel, & Nederhof, 2017).
The clinical implication is not that symptoms are always appropriate. It is that effective treatment should investigate their function and history before attempting to eliminate them.
5. Allostatic load: when adaptation becomes biologically expensive
Allostasis means achieving stability through change. The body adjusts heart rate, attention, muscle readiness, hormones, immune activity and energy allocation to meet changing demands.
These responses are essential in the short term. The problem develops when the organism must remain activated for months or years.
This cumulative physiological burden is often described as allostatic load: the wear and tear associated with repeated or prolonged adaptation. Possible effects include:
- Persistent sympathetic activation
- Disrupted sleep and impaired recovery
- Endocrine changes
- Inflammatory activity
- Cognitive fatigue
- Reduced concentration and working memory
- Emotional exhaustion
- Increased vulnerability to physical and psychological illness
The stress response has not necessarily “failed” because it responded. It may have been required to respond too often, with too little opportunity for recovery.
McEwen’s foundational work on stress, adaptation and disease describes how allostatic systems can be protective in the short term while contributing to illness when chronically activated (McEwen, 1998).
This is why therapy should not focus only on changing thoughts. It may also need to address sleep, physical health, workload, relationships, safety and the conditions that keep the nervous system activated. Keystone Therapy’s stress and sleep services and mind-body integration approach reflect this broader brain–body perspective.
6. Distress may be proportionate to the environment
The language of “resilience” can sometimes place too much responsibility on the individual.
If an employee becomes distressed in an abusive workplace, the problem may not be insufficient resilience. If a child is repeatedly exposed to fear, humiliation or neglect, teaching coping skills cannot substitute for improving the environment. If someone is living under coercive control, emotional-regulation training alone does not remove the source of danger.
A crucial clinical principle is:
Before locating pathology within the individual, assess whether the distress is a disproportionate internal dysfunction or a proportionate response to pathogenic circumstances.
When the environment is actively harmful, environmental change becomes part of treatment. This may involve:
- Establishing physical and relational safety
- Setting boundaries
- Seeking workplace or educational support
- Addressing coercive or abusive dynamics
- Improving housing or financial stability where possible
- Building reliable social connection
- Reducing avoidable demands
- Connecting with medical, legal or community services
Therapy can support these decisions, but therapy should not be used to help a person tolerate conditions that remain dangerous.
7. Sensitivity is not simply vulnerability
People respond differently to similar environments. Some nervous systems are more environmentally sensitive than others. High sensitivity may amplify the impact of adversity, but it may also amplify the benefits of safety, support and meaningful connection.
This is sometimes described as differential susceptibility: an individual may experience more difficulty in a harsh environment and more benefit in a supportive one.
Sensitivity may express itself as:
- Strong emotional responses
- Heightened awareness of interpersonal cues
- Deep engagement with interests
- Greater response to criticism or rejection
- Increased vulnerability to sensory or social overload
- Stronger learning from relational experiences
For neurodivergent people, the issue may also involve a mismatch between the person’s nervous system and environments designed around narrow assumptions about attention, communication, sensory processing or social behaviour. Neurodiversity-affirming support should ask not only, “How do we make this person fit the environment?” but also, “What changes would make the environment more accessible?”
Keystone Therapy provides neurodiversity-affirming support in Perth for people navigating ADHD, autism and related emotional-regulation challenges.
8. Plasticity creates the possibility of recalibration
Developmental history matters, but it does not make a person permanently fixed. Plasticity: the capacity of biological systems to change in response to experience: creates the possibility of recalibration.
The nervous system may gradually update its predictions through repeated experiences of:
- Safety
- Predictability
- Secure relationships
- Restorative sleep
- Belonging
- Autonomy
- Meaningful work
- Embodied awareness
- Successful, carefully paced therapy
- Distress that is experienced without catastrophe
Therapy can therefore be understood as guided recalibration. A consistent therapeutic relationship provides new environmental information. Reliable boundaries provide information. Co-regulation provides information. Exposure undertaken at an appropriate pace provides information. Experiencing emotion without rejection or collapse provides information.
The brain does not learn safety only because someone explains it. It learns safety because safety is experienced repeatedly.
9. Moving mental health upstream
If mental health develops through organism–environment interaction, prevention cannot be confined to clinical services.
Schools are mental-health environments. Workplaces are mental-health environments. Housing, transport, urban design, economic security, parenting support and community connection all influence the conditions under which nervous systems develop and recover.
This does not reduce the importance of individual therapy. It clarifies its place alongside biological care, relational repair and social change.
The future-facing question is not only:
How do we make individuals more resilient?
It is also:
What kinds of environments allow human nervous systems to develop, regulate, recover and flourish?
That is where preventive psychology begins.
If you would like to explore how developmental history, brain-based therapy, lifestyle factors and current environmental demands may be interacting in your life, you can contact Keystone Therapy or book an appointment.
Email info@keystonetherapy.com.au for a free copy of the book.
Important note
This article is educational and does not provide a diagnosis or replace medical or psychological care. Symptoms may have multiple causes, including biological, developmental, psychological and environmental factors. If you are experiencing significant distress, ongoing trauma symptoms, risk of harm or changes in functioning, speak with a qualified health professional. In an emergency in Australia, call 000; for crisis support, contact Lifeline on 13 11 14.
References
- Bateson, P., et al. (2004). Developmental plasticity and human health. Nature, 430, 419–421. https://doi.org/10.1038/nature02725
- Del Giudice, M., Ellis, B. J., & Shirtcliff, E. A. (2011). The Adaptive Calibration Model of stress responsivity. Neuroscience & Biobehavioral Reviews, 35(7), 1562–1592. https://pmc.ncbi.nlm.nih.gov/articles/PMC3068241/
- Ellis, B. J., Oldehinkel, A. J., & Nederhof, E. (2017). The adaptive calibration model of stress responsivity. Development and Psychopathology, 29(3), 1001–1021. https://doi.org/10.1017/S0954579416000985
- McEwen, B. S. (1998). Stress, adaptation, and disease: Allostasis and allostatic load. Annals of the New York Academy of Sciences, 840, 33–44. https://pubmed.ncbi.nlm.nih.gov/9629234/
- O’Connor, T. G., et al. (2005). Prenatal anxiety predicts individual differences in cortisol in pre-adolescent children. Biological Psychiatry, 58(3), 211–217. https://pubmed.ncbi.nlm.nih.gov/16084841/
