Psychological state and physical health: how the mind affects the body

It wasn't a sudden pain or a dramatic illness. It was something much more subtle, and for that very reason, more unsettling. First, a pressure in her chest that appeared without warning. Then, a fatigue that wouldn't go away even after eight hours of sleep. Later, digestive problems, constant tension in her neck, a vague feeling of something malfunctioning internally that no medical test could explain. The blood tests came back normal. The MRIs were clear. "You're fine," they told her. And yet, her body persisted.

For months she lived with the unsettling suspicion that it wasn't all in her head, but it also didn't fit the description of a classic illness. Her life continued on the surface (work, responsibilities, deadlines...), but inside, something was amiss. The stress wasn't an isolated incident; it was her baseline state. The anxiety didn't shout; it whispered. And her body, far from being a passive observer, began to speak the language it knew best: the language of symptoms.

This article explores precisely that uncomfortable territory where psychology and biology intersect. It analyzes how chronic stress alters key physiological systems, why some unexpressed emotions end up manifesting physically, what role the nervous and immune systems play in this process, and why not everyone becomes equally ill under the same pressure.

Because sometimes illness doesn't arrive as an external enemy, but as an internal message that we have been ignoring for too long.

Are we listening to what our body is trying to tell us?

When the mind speaks, the body listens

For decades, the mind-body relationship has oscillated between two uncomfortable extremes: either it has been treated as an almost mystical truth (“it’s all in your head”) or it has been ignored in the name of a biology reduced to organs, tissues, and blood tests. Modern psychology and biology have dismantled both simplifications, and today we know that the psychological state does not float on an abstract plane, separate from the body, but rather translates into measurable biochemical signals, neural activations, and immune responses.

From a psychological perspective, concepts such as stress, anxiety, or perception of control are not only understood as subjective experiences, but as processes that modulate the way the brain evaluates threats, anticipates consequences, and regulates behavior.

This psychological evaluation activates specific biological systems: the hypothalamic-pituitary-adrenal axis releases cortisol, the autonomic nervous system adjusts sympathetic and parasympathetic tone, and the immune system responds with inflammatory changes.

Modern biology understands the body as an active system that interprets the environment through the brain. Thus, symptoms such as pain, inflammation, or fatigue depend not only on visible injuries but also on how chronic stress regulates the neuroendocrine and immune systems, demonstrating that mind and body function as an adaptive unit.

Discussing the mind-body connection from the perspectives of psychology and biology does not imply denying organic illness or blaming the individual for their discomfort. It implies something more uncomfortable and more scientific: accepting that psychological states have a real capacity to modulate biological processes, and that these processes, in turn, feed back into the psychological experience.

Chronic stress: the silent switch of many diseases

When the body perceives a threat (real or anticipated), one of the finest and oldest response systems we have is activated: the hypothalamic-pituitary-adrenal (HPA) axis.

From a biological perspective, its function is brilliant. From the perspective of modern life, it's sometimes a problem. Its function is adaptive: to allow a rapid response to stress. The problem isn't the system itself, but its prolonged activation in contexts of chronic psychological stress, for which it isn't biologically designed.

In response to stress, the hypothalamus releases CRH, the pituitary gland secretes ACTH, and the adrenal glands produce cortisol. In the short term, this glucocorticoid mobilizes energy, regulates inflammation, and promotes adaptation. However, when activation is prolonged, the HPA axis becomes dysregulated. Both a sustained excess of cortisol and blunted responses, indicative of an overtaxed system, can be observed.

This dysregulation translates into allostatic load, the physiological cost of keeping adaptation mechanisms activated for too long. One of its most significant effects occurs in the immune system. Although cortisol is anti-inflammatory, chronic exposure can lead to glucocorticoid resistance, allowing low-grade inflammation to persist. This state has been linked to fatigue, chronic pain, mood disorders, and increased susceptibility to disease.

The associated physiological wear and tear doesn't usually manifest as a clear injury, but rather as diffuse and persistent symptoms: unrefreshing sleep, muscle aches, digestive problems, or constant exhaustion. These aren't imagined symptoms, but signs of an organism that has lost precision in its self-regulation.

From a biopsychosocial perspective, the HPA axis is a direct bridge between psychological experience and the body's biology. Sustained mental states of threat, hypervigilance, or cognitive rumination translate into real hormonal and inflammatory changes.

Physiological wear and tear does not appear abruptly: it is the cumulative result of an adaptive system that has functioned in emergency mode for too long.

Emotions that manifest physically: when psychological distress becomes a physical symptom

Somatization is one of those unsettling concepts because it breaks down a deeply ingrained boundary: the idea that if there's no visible injury, the symptom can't be real. Scientific evidence says exactly the opposite. In somatization, the body isn't faking, it's responding. And it does so using the same neurobiological circuits involved in pain, inflammation, and stress regulation.

We use the terms somatic symptom disorders and functional pain to refer to persistent physical symptoms that are not fully explained by a structural injury, but which cause real suffering. Pain, fatigue, dizziness, digestive discomfort, or a feeling of tightness in the chest are common examples. The key is that these symptoms don't appear out of nowhere; they are sustained by a complex interaction between the brain, nervous system, endocrine system, and immune system.

The body isn't inventing anything. It's reacting to a system that's been on high alert for too long.

A classic example is chronic functional pain. In conditions like fibromyalgia or chronic nonspecific low back pain, imaging tests may not show relevant damage, but the pain is intense and constant. Science has shown that in these cases there is central sensitization; the nervous system amplifies pain signals. Psychological factors such as anxiety, depression, or prolonged stress do not cause the pain on their own, but they lower the threshold at which the brain interprets a bodily signal as painful. The result is a body that overreacts.

Another prime example is irritable bowel syndrome. There is no visible inflammation or clear lesions, but there is persistent abdominal pain, diarrhea, or constipation. Studies show that the gut-brain axis is profoundly influenced by psychological stress. People with high levels of anxiety or a history of early stress exhibit greater visceral reactivity: the gut responds excessively to normal stimuli. The symptom is not imagined; it is a maladaptive physiological response.

Chronic fatigue and certain functional syndromes share a similar pattern. Alterations in the HPA axis, low-grade inflammation, and changes in body perception combine with psychological states of sustained threat. The body enters an energy-saving mode, generating extreme tiredness, brain fog, and diffuse pain. From the outside, it may seem inexplicable; from the inside, it is profoundly limiting.

An interesting finding is that many patients with somatization exhibit interoceptive hypervigilance, paying intense and constant attention to bodily signals. This is not a voluntary trait, but rather a learned behavior of the nervous system. The more a sensation is monitored, the more relevant it becomes to the brain, and the more intensely it is perceived. It is the same mechanism by which an almost imperceptible noise becomes unbearable when someone tells you, “Listen to that.”

Talking about psychosomatic disorders doesn't mean reducing illness to the psychological aspect, but rather broadening the focus. It means accepting that pain can exist without visible damage, that the body can become ill due to regulatory exhaustion, and that physical symptoms can be the final expression of a system subjected to prolonged stress.

Immune system and psychological state: a deeper relationship than it seems

Psychoneuroimmunology is the field that studies how psychological processes, the nervous system, and immunity interact continuously and measurably. The brain does not passively observe the immune system, but actively regulates it through hormonal and neural pathways.

Psychological stress is a clear example. When faced with a threat, the HPA axis and the autonomic nervous system are activated, which alters the release of inflammatory cytokines. In situations of acute stress, this response can be adaptive. The problem arises with chronic stress, which is associated with persistent low-grade inflammation, related to symptoms such as fatigue, diffuse pain, sleep disturbances, and mood changes.

A key concept is sickness behavior. When the immune system is activated, it sends signals to the brain that induce behaviors typical of illness: fatigue, social withdrawal, and loss of motivation. This biological program is useful during an infection, but it can be activated continuously without clear pathogens, as occurs in depression, chronic pain, or somatization.

Research also shows that a subgroup of people with depression exhibit elevated inflammatory profiles. In these cases, depression is not only a psychological phenomenon but also an immunological one, and it is associated with a poorer response to conventional antidepressant treatments.

Psychoneuroimmunology also explains why stress worsens physical illnesses. In autoimmune diseases, for example, stress does not cause the disease, but it can modulate the intensity of flare-ups by altering immune regulation.

The most important aspect is that this communication is bidirectional: the immune system informs the brain through cytokines and nerve pathways such as the vagus nerve, influencing energy, pain, and motivation. Emotions do not create diseases, but they can modify the biological terrain in which they develop.

Brain, nervous system and organs: the role of the autonomic nervous system

The brain doesn't direct the body like a distant boss, but rather like a real-time regulator that constantly adjusts organ activity through the autonomic nervous system (ANS). This system operates automatically and connects psychological state with basic functions such as heart rate, digestion, breathing, and muscle tone. Every emotion, every perception of threat or safety, translates into electrical and chemical changes that reach the heart, gut, or immune system in a matter of seconds.

The ANS is organized into two main branches: the sympathetic system, responsible for activation, and the parasympathetic system, responsible for recovery and maintenance.

The sympathetic nervous system prepares the body for action: it accelerates the heart rate, diverts blood to the muscles, and inhibits non-urgent processes such as digestion. It is essential for survival. The problem arises when this state becomes chronic. People subjected to prolonged stress show persistent sympathetic activation associated with hypertension, digestive problems, muscle tension, and increased sensitivity to pain.

The parasympathetic nervous system, largely mediated by the vagus nerve, acts as a physiological brake. It reduces heart rate, facilitates digestion, and promotes states of calm and repair. Interestingly, heart rate variability, a marker of healthy vagal tone, is associated with better emotional regulation, less inflammation, and a better cardiovascular prognosis. When the parasympathetic nervous system fails to counteract sympathetic activation, the body loses regulatory flexibility.

This dynamic explains many functional symptoms. Irritable bowel syndrome, for example, is related to impaired communication between the brain and the digestive tract, where the sympathetic nervous system dominates and the parasympathetic nervous system does not adequately regulate intestinal motility. Similarly, palpitations, dizziness, or shortness of breath can occur without structural pathology, but with a nervous system stuck in a state of alert.

Body regulation does not depend on an isolated organ, but on the dynamic balance between the brain, the autonomic nervous system and organs, a balance that can be broken without any visible injury, but with very real physical consequences.

Why do some people get sicker under pressure than others?

Under similar levels of pressure, not everyone becomes ill in the same way. Stress doesn't act as a universal agent, but rather as an amplifier of pre-existing vulnerabilities. Two individuals can experience the same work or emotional situation and exhibit very different biological responses. The key lies in how their nervous and endocrine systems have learned to respond to the threat over time.

One of the key factors is individual vulnerability, which includes personality traits such as neuroticism, rumination, and a low sense of control. These profiles are associated with more intense and prolonged activation of the HPA axis and the sympathetic nervous system. In practice, this translates to greater cortisol exposure, poorer physiological recovery, and more low-grade inflammation. For example, individuals with high rumination tendencies show greater persistence of stress even after the triggering event has resolved.

Psychological trauma, especially in early life, is another powerful modulator. Adverse childhood experiences have been linked to lasting programming of the stress system: exaggerated or, conversely, underactivated HPA axis responses in adulthood. These patterns are associated with a higher risk of chronic pain, functional disorders, and inflammatory diseases. It's not that trauma directly causes disease, but rather that it leaves a biological system that is more reactive and less flexible in the face of new demands.

The social and environmental context completes the picture. Social support, economic stability, and a sense of security mitigate the impact of stress on the body. Conversely, sustained pressure without the possibility of recovery, for example, in hostile work environments or precarious situations, keeps the body in a state of alert. A relevant finding is that social support is associated with less inflammation and better regulation of the autonomic nervous system. In short, becoming ill under pressure depends not only on the cause of the stress, but also on how each individual, with their history and context, can or cannot adapt to it.

Can you heal your body by taking care of your mind? What science says (and what it doesn't)

The idea that the body can be healed by caring for the mind is appealing, but science requires some qualification. Psychological interventions do not replace medical treatments, nor do they eliminate diseases on their own. What they can do is modulate key biological processes involved in pain, inflammation, stress regulation, and functional recovery.

The difference between science and magical promise lies precisely there: in talking about regulation and improvement, not miraculous cures.

Among the interventions with the strongest empirical support is cognitive behavioral therapy (CBT). In chronic pain, fatigue syndrome, or somatic symptom disorders, CBT has been shown to reduce the intensity of discomfort, improve functionality, and decrease associated anxiety and depression. It does not eliminate the symptom, but it helps break the cycle of bodily hypervigilance, avoidance, and stress that perpetuates it. Interestingly, patients who learn to reinterpret bodily signals tend to show less activation of the HPA axis and better pain tolerance.

Mind-body interventions, such as mindfulness, meditation, and relaxation techniques, also have supporting evidence, although their effects are more modest. Meta-analyses indicate small to moderate improvements in pain, sleep quality, and overall well-being. These benefits are explained by improved regulation of the autonomic nervous system, with increased parasympathetic tone and reduced sympathetic stress response. Again, there's no magic bullet: the effect appears with sustained practice and as a complement to, not a substitute for, medical treatment.

What science doesn't support is the idea that a positive attitude, visualization, or positive thinking can cure illnesses on their own. Nor does it support blaming the patient when they don't improve. The evidence points to something more sober and more useful: taking care of the mind can reduce physiological wear and tear, improve quality of life, and facilitate recovery, but always within a holistic approach. The question isn't whether the mind heals the body, but how better psychological regulation can help the body stop fighting against itself while the actual illness is being treated.

Final thought: not everything is in your head, but nothing happens without it.

For too long, a false dilemma has been posed: either the problem is “organic” or it’s “in your head.” Current science supports neither extreme. The body doesn’t invent symptoms, but neither does it function independently of the brain. Pain, fatigue, inflammation, or persistent discomfort are real experiences that emerge from complex biological systems, regulated largely by how the organism interprets and responds to its environment. To deny any of these dimensions is to oversimplify something that, by definition, is not simplistic.

Saying that not everything is in your head is important because it protects the patient from stigma and guilt. But accepting that nothing happens without it is just as necessary, even if it's uncomfortable. The brain isn't a passive observer of illness: it regulates hormones, modulates inflammation, adjusts the autonomic nervous system, and gives meaning to the body's signals. When that system is on high alert for too long, wear and tear appears, even without a visible injury.

Understanding this shouldn't lead to promising miraculous cures or shifting responsibility from the healthcare system to the individual. It should lead to something more humane: broadening our perspective, integrating psychology with biology, and ceasing to treat symptoms as if they existed in isolated compartments. Caring for the mind doesn't replace treating the body, but ignoring it often has a real physical cost.

What would change in the way we understand illness and support those who suffer if we stopped artificially separating mind and body?

FAQs about psychological state and physical health

Why do some people get sicker than others under the same pressure?

Individual factors such as biological vulnerability, personality traits, prior trauma experiences, and social context all play a role. These elements determine how the nervous and endocrine systems respond to stress, causing some people to accumulate more physiological strain than others.

What role does the autonomic nervous system play in these symptoms?

The autonomic nervous system regulates basic functions such as heart rate, digestion, and breathing. When sympathetic activation (a state of alertness) predominates chronically, symptoms such as palpitations, digestive problems, pain, or a constant feeling of exhaustion may appear, even without organic damage.

Can psychological therapy cure a physical illness?

Not in the magical sense of the term. Psychological interventions do not replace medical treatments or eliminate diseases. What they can do is reduce discomfort, improve stress regulation, decrease low-grade inflammation, and increase quality of life, facilitating recovery.

Which psychological treatments have real evidence?

Cognitive behavioral therapy is the most supported treatment for chronic pain, fatigue, and somatic symptom disorders. Mind-body interventions such as mindfulness or relaxation also show modest but consistent benefits, especially as an adjunct to other treatments.

Does saying that the mind influences the body not blame the patient?

It shouldn't be done. Current science rejects the idea of blame. Acknowledging the influence of the mind means broadening the approach, not blaming the individual. The goal is to better understand the mechanisms involved in order to treat the patient in a more humane and holistic way.

What concrete examples exist of somatized illnesses or symptoms?

There are numerous well-documented examples. Among the most common are chronic functional pain (such as fibromyalgia or lower back pain without a clear structural lesion), irritable bowel syndrome, chronic fatigue, tension headaches, functional palpitations, and certain persistent dizzinesses. It is also very common for a patient to somatize a heart attack, experiencing all its symptoms, but when they go to the emergency room, it is determined to be anxiety and not an actual heart attack.

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