The origin of human help-seeking behaviour predates language, religion, and civilisation itself. It arises from suffering and pain, one of the primitive impulses shared across the human species.
Pain is a deeply subjective experience, and two individuals with identical injuries may describe very different levels of suffering.
This variability reflects the complex interplay between biological, psychological, and social factors that shape the human experience of pain. Our scientific understanding of pain has evolved over centuries, moving gradually from philosophical interpretation to modern neurobiological models.
The International Association for the Study of Pain defines pain as “an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage.”
This definition emphasises an important insight: pain is not merely a physical sensation but also an emotional and cognitive experience. In this chapter, we explore the evolution of key ideas and concepts about pain, including how our thoughts and perceptions shape the way we understand and treat it.
Ancient philosophy to modern medicine
Human beings enter the world through a painful process, and suffering has been an inseparable part of human life. The meaning given to pain has often reflected the cultural and intellectual framework of the era in which it was interpreted.
The word pain itself derives from the Latin “poena”, meaning punishment. Historically, suffering was sometimes interpreted as divine punishment, and relief was sought through prayer or spiritual practice.
In ancient Chinese philosophy, illness and pain were understood as disruptions in the balance between yin and yang. These opposing yet complementary forces governed the flow of qi and blood within the body. Pain was believed to occur when this balance was disturbed, leading to therapies designed to restore harmony within the body.
Ancient Egyptian medicine offered a different interpretation. Egyptians believed that the heart, rather than the brain, was the centre of emotion, memory, and thought. Consequently, painful experiences were interpreted as disturbances of the heart, sometimes attributed to spiritual forces acting upon it. Also, Galen, and Aristotle prominent Greek thinkers described pain as an emotional experience or “a passion of the soul”.
An influential concept that persisted from antiquity until the nineteenth century was the theory of the four humours. According to this doctrine, the body contained four fundamental fluids: blood, phlegm, yellow bile, and black bile, whose balance determined health. Disease and pain were thought to arise from imbalances among these humours. Treatments therefore aimed to restore equilibrium through the application of “opposites.” For example, headaches believed to be caused by cold humours might be treated with heat.
A significant intellectual shift occurred with the work of Hippocrates and his followers who began to analyse pain as a clinical variable rather than solely a philosophical or spiritual phenomenon. They carefully described pain using specific characteristics such as location, duration, and association with other symptoms. These observations allowed physicians to infer underlying disease processes and many descriptive terms for pain used today, originate from this early clinical tradition.
During the Middle Ages, pain again acquired a strongly spiritual interpretation, particularly within Christian theology. Pain was often viewed as a test of faith or a form of spiritual purification. Religious imagery frequently depicted tortured saints with serene or ecstatic expressions, suggesting that suffering could bring individuals closer to God. Similar interpretations are also reflected in Hindu traditions, where illness was sometimes seen as a consequence of wrongdoing or divine will. A well-known example is the Tamil Saivite saint Thirunavukarasar (Appar), who is believed to have suffered severe stomach pain as part of a divine trial, with relief attributed to his devotional hymn Kootraayinavaaru. Across these traditions, pain was not merely a physical experience but a deeply spiritual one, often intertwined with moral, religious, and existential meaning.
Pain has also reflected prevailing social structures. A striking historical example is the rise and fall of the diagnosis of hysteria. In 19th century Europe and America, hysteria was widely diagnosed and characterised by unexplained pain and other symptoms. The condition was observed almost exclusively among middle- and upper-class women and was treated through strict social isolation, confinement to bed, and prohibition of intellectual activity. As educational opportunities and social roles for women expanded, the diagnosis gradually disappeared, illustrating how cultural context can shape the interpretation of pain.
Another early attempt to link mind and body in the understanding of pain emerged in the work of the German physician Franz Mesmer. In 1766 he published his dissertation titled “On the Influence of the Planets on the Human Body”. Mesmer believed he had discovered an invisible fluid, which he termed “animal magnetism”. He proposed that this fluid permeated and surrounded all living bodies and claimed that by manipulating its flow, he could influence health and heal patients.
Further developments in understanding the relationship between mind and body came with the work of Sigmund Freud, whose theories emphasised the influence of unconscious psychological processes on physical symptoms. Freud proposed that emotional conflicts could manifest as bodily symptoms through mechanisms such as conversion disorders, thereby providing a psychological explanation for certain forms of pain without identifiable physical injury.
These early explorations of the mind–body interface eventually led to the development of cognitive-behavioural approaches to pain therapy in the 1980s. These methods focus on helping patients develop coping strategies and adaptive behavioural responses to chronic pain. Modern research continues to explore the influence of social context, gender, cultural background, and psychiatric comorbidities on the experience of pain.
Mechanistic understandings
While philosophical traditions emphasised holistic interpretations of pain, another intellectual tradition emerged that viewed the human body as a biological machine. Within this mechanistic framework, pain was interpreted as the result of structural or functional disturbances within the body.
Early anatomical investigations by Galen of Pergamum (130–201 AD) and Avicenna (980–1037 AD) helped establish the idea that pain might arise from physical structures rather than spiritual forces. Their work laid the foundation for later scientific exploration of the nervous system, although this was challenged later in the Renaissance era.
The rise of empirical scientific inquiry encouraged physicians to investigate the biological basis of sensation through observation and experimentation. Wartime injuries across Europe provided opportunities for surgeons to study wounds caused by bullets and musket balls. These injuries required surgical removal of foreign bodies and often resulted in amputations, prompting deeper investigation into the physiological origins of pain.
A major scientific milestone occurred in 1811 when Scottish anatomist and surgeon Charles Bell published a monograph describing the functional distinction between sensory and motor nerves. Bell proposed that the nerves responsible for sensation were separate from those controlling movement. In 1822, François Magendie confirmed this concept experimentally by demonstrating that sectioning the dorsal roots of the spinal cord resulted in loss of sensation in the corresponding limbs. These discoveries became known as the Bell–Magendie law, the fundamental principle of neurophysiology which was confirmed by Johannes Müller in 1831.
Subsequent research continued to refine the mechanistic understanding of sensory pathways. In 1858 Moritz Schiff demonstrated that separate spinal pathways transmitted different types of sensations, including touch, temperature, and pain. Based on these findings, Schiff proposed that pain should be considered a distinct sensory modality.
At the turn of the twentieth century, Max von Frey conducted detailed investigations of the skin as a sensory organ. Using pig bristles and horsehair filaments of varying stiffness, he systematically mapped pressure and pain points on the skin. Von Frey concluded that distinct receptors within the skin responded to different forms of stimulation, such as pressure, warmth, cold, and pain. This work strengthened the view that specialised sensory structures were responsible for detecting different types of stimuli.
The contributions of the British physiologist Charles Scott Sherrington further advanced this field. Sherrington introduced the term “nociception” to describe the neural process of encoding potentially harmful stimuli and identified specialised sensory receptors known as nociceptors that respond to tissue-damaging stimuli.
Despite these advances, scientists continued to debate the mechanisms underlying pain perception. Some investigators proposed that pain resulted from the summation of sensory signals within the spinal cord rather than from a specific pathway.
These ideas ultimately contributed to one of the most influential theories in pain science: the Gate Control theory. Introduced in 1965 by Ronald Melzack and Patrick Wall while working at the Massachusetts Institute of Technology, U.S., this theory proposed that incoming pain signals are modulated within the spinal cord before reaching the brain. According to the model, sensory information arriving through small C fibres can be inhibited by activity in larger Aβ fibres, effectively “closing the gate” to pain signals. The theory also proposed that signals descending from the brain could influence this gating mechanism.
Although some aspects of the Gate Control theory were later revised, its introduction represented a seminal moment in the scientific study of pain and stimulated decades of research into neural mechanisms and therapeutic interventions.
Treatments for pain
Throughout history, approaches to pain treatment have reflected the prevailing philosophical views of physicians. Some practitioners emphasise helping patients adapt psychologically and socially to their pain, while others focus on identifying anatomical sources and treating them through targeted interventions.
Before the 18th century, therapies for pain were largely nonspecific and included acupuncture, bloodletting, purging, herbal remedies, and distraction through the creation of competing painful stimuli. Physicians also attempted to classify the causes of pain to guide treatment. During the reign of the Roman emperor Trajan, a physician recorded 13 causes of pain. Avicenna later described 15 causes, while Samuel Hahnemann, the founder of homeopathy, listed 75.
The development of pharmacology gradually transformed pain management. Alcohol and opium were among the earliest substances used for pain relief. In the mid-seventeenth century, Thomas Sydenham developed laudanum, a mixture of sherry or wine combined with opium, saffron, cinnamon, and cloves, which became widely used for conditions ranging from dysentery to gout.
In South America, coca leaves were traditionally chewed to relieve fatigue and pain. The active alkaloid cocaine was isolated in the 1860s by Albert Niemann, and in 1884 Carl Koller demonstrated its effectiveness as a local anaesthetic during eye surgery.
Another major advance occurred when German pharmacist Friedrich Sertürner isolated morphine from opium in 1806, identifying what he called the “soporific principle” responsible for opium’s analgesic effects.
The history of aspirin provides another example of scientific progress. The analgesic properties of willow bark were first reported scientifically in 1763 by Reverend Edmund Stone. In 1829 the French pharmacist Henri Leroux isolated the active compound from willow bark, and in 1853, French chemist Charles Frédéric Gerhardt synthesised acetylsalicylic acid, later known as aspirin. Clinical benefits of this compound in treating acute rheumatism were reported by Scottish physician Thomas J. MacLagan in 1876.
Technological innovations also transformed pain treatment. The development of the hypodermic needle by Rynd and the syringe by Wood allowed physicians to inject analgesic medications directly into the body. Surgical anaesthesia advanced dramatically in the years after Crawford Long first used ether anaesthesia in 1842 and William Morton publicly demonstrated ether anaesthesia in 1846.
Other treatments arose from observations of injured patients. Ambroise Paré, a Renaissance surgeon, described persistent pain after limb amputation centuries before the concept of phantom limb pain was formally recognised. During the American Civil War, Silas Weir Mitchell studied nerve injuries and in 1864 and he and his colleagues described a severe burning pain following nerve damage, later coining the term causalgia.
Later developments included nerve injections for pain relief. In 1903 Schloesser used alcohol injections to interrupt nerve conduction in patients with facial neuralgia. Surgeons in the early twentieth century performed nerve ablation procedures for chronic pain syndromes, while anaesthesiologists began experimenting with local anaesthetic nerve blocks.
Modern treatments for pain now include spinal cord stimulation, sympathetic nerve blocks, radiofrequency modulation, and cognitive therapies that address the complex interplay between peripheral nerve signals and central nervous system processing.
Pain medicine as a specialty
The development of pain medicine as a formal specialty reflects the growing recognition that pain is a complex multidimensional experience requiring interdisciplinary care. Sociologist Isabelle Baszanger described two contrasting approaches to pain treatment observed in clinics in Paris. One approach focuses on curing through technical interventions directed at physiological abnormalities, while the other emphasizes healing through psychological adaptation and behavioural strategies.
The first outpatient clinic devoted specifically to chronic pain was established by Emery A. Rovenstine at Bellevue Hospital in New York in 1936. However, the founding father of interdisciplinary pain management is widely considered to be John J. Bonica. In 1947 Bonica established the first multidisciplinary clinic for the treatment of complex pain conditions in wounded World War II veterans in Seattle.
In 1953 he published the first edition of his landmark textbook “Management of Pain”, which helped establish pain medicine as a legitimate field of medical study. Bonica’s work expanded significantly after he joined the University of Washington in 1960. His international advocacy culminated in the multidisciplinary conference held in Issaquah, Washington, in May 1973. This meeting ultimately led to the establishment of the International Association for the Study of Pain. The recognition of pain medicine as a medical subspecialty followed in subsequent decades.
Today, pain medicine integrates insights from neuroscience, psychology, pharmacology, rehabilitation medicine, and interventional procedures. Advances in molecular biology, genetics, and neuroimaging now allow scientists to research on how the nervous system processes pain in real time. These technologies continue to expand our understanding of pain mechanisms and open up new possibilities for treatment.
(Dr. Vasanth Kattalai Kailasam, is a pain medicine and interventional pain management specialist at Mercy Health, Illinois, U.S., and faculty member at the University of Illinois, Chicago.)
(This article was first published in The Hindu’s e-book, Pain and Relief: Demystifying the Science of Suffering)