Pain is a complex and subjective experience, defined as an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage. Crucially, the perception and experience of What Is Pain varies significantly from person to person, even when the underlying cause is similar. Therefore, an individual’s self-report of their pain is considered the most reliable measure. The intensity of pain can range from mild discomfort to excruciating agony, and the sensations can manifest as pricking, tingling, stinging, burning, shooting, aching, or electric shocks.
Pain serves a vital protective function, acting as an alarm system that alerts us to potential or actual harm. It can signal the presence of underlying medical conditions, such as cancer, or teach us to avoid dangerous situations, like touching a hot stove. However, pain can also persist even when there is no identifiable cause or apparent benefit. Pain lasting longer than three months is classified as chronic pain. Chronic pain can develop spontaneously or linger after an injury has healed, significantly impacting a person’s mood, relationships, mobility, and overall quality of life. Everyday tasks, work, and leisure activities can become challenging or impossible to manage due to what is pain.
Classifying Pain: Patterns and Types
Pain can be categorized based on its duration and frequency, as well as its underlying source.
Pain Patterns
- Acute Pain: This type of pain has a sudden onset and resolves when the underlying cause is treated or healed. Acute pain is typically sharp and acts as a warning signal of a threat to the body. Common causes include muscle strains, bone fractures, dental procedures, surgery, childbirth, infections, and burns.
- Episodic Pain: Episodic pain occurs intermittently, potentially at irregular intervals. It can be associated with chronic medical conditions, such as sickle cell disease or chronic migraine. Episodic pain may arise spontaneously or be triggered by specific factors.
- Chronic Pain: Chronic pain persists for more than three months or beyond the expected healing time. In some cases, acute pain may transition into chronic pain. It is also possible for chronic pain to develop without a known cause. Individuals can experience one or more chronic pain conditions simultaneously, or both chronic and acute pain.
Pain Types Based on Source
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Nociceptive Pain: This type of pain results from tissue damage and/or inflammation. The sensations can vary from sharp and pricking to dull and aching, depending on the nature of the injury or inflammation. Examples include pain from a paper cut, infection, broken bone, or osteoarthritis.
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Neuropathic Pain: Neuropathic pain is caused by damage to the nerves, often described as burning, tingling, shooting, or electric shock-like sensations. Conditions that can cause neuropathic pain include diabetic neuropathy, shingles, and sciatica.
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Nociplastic Pain: This type of pain arises from changes in the way the nervous system processes pain. These changes are not associated with identifiable injury, tissue damage, inflammation, or disease. The sensations associated with nociplastic pain vary widely. Examples include fibromyalgia, irritable bowel syndrome, and chronic low back pain.
What Causes Pain? The Biopsychosocial Model
The understanding of what causes pain, and why people experience it differently, is still evolving. Acute pain with a clear cause (e.g., infection, fracture) is better understood than chronic pain. Research emphasizes that biological, psychological, and social factors all contribute to an individual’s pain experience. This integrated perspective is known as the biopsychosocial model of pain.
- Biological factors include brain function, genetics, the nervous system, the immune system, and the endocrine system.
- Psychological factors encompass mood, stress, beliefs about pain, and coping mechanisms.
- Social factors relate to social support, access to healthcare, and environmental conditions.
These factors are interconnected, influencing each other and shaping the overall experience of pain. Consequently, effective pain management requires a holistic and individualized approach.
The Role of Genetics and Epigenetics
Our genetic makeup, inherited from our parents, influences our susceptibility to pain and how we respond to pain treatments. However, lifestyle factors, environmental exposures, and medical conditions can alter gene expression, turning genes “on” or “off” – a process known as epigenetics. Research suggests that epigenetic changes resulting from physical activity can positively influence pain, while intense emotional stress can worsen pain outcomes. Social determinants of health, like neighborhood, access to healthy food, and quality healthcare, also contribute to disparities in pain experiences through epigenetic mechanisms.
The Nervous System and Pain
The nervous system, comprised of the central nervous system (brain and spinal cord) and the peripheral nervous system (nerves extending to the rest of the body), plays a central role in pain perception. The brain regions involved in pain processing overlap with those responsible for emotions, motivation, attention, memory, and sensation. Changes in these brain systems can increase the risk of chronic pain. Peripheral and central sensitization, characterized by increased sensitivity to pain and other sensations, can develop after an injury, contributing to chronic pain.
Symptoms of Nervous System Sensitization
- Hyperalgesia: Increased pain sensitivity to stimuli that are already painful.
- Allodynia: Pain response to stimuli that are normally not painful (e.g., light touch on sunburned skin).
- Global sensory hyperresponsiveness: Heightened sensitivity to a wide range of sensations, including light, noise, smells, and food.
The Immune System and Inflammation
The immune system protects the body against infection and injury through inflammation. While inflammation is essential for healing, excessive or prolonged inflammation can contribute to chronic pain. Autoimmunity, where the immune system attacks healthy cells, can also lead to chronic inflammation and pain.
The Endocrine System and Hormones
The endocrine system produces hormones that regulate various bodily functions. Stress hormones, such as cortisol and adrenaline, can modulate pain intensity. Chronic pain can also alter endocrine system function over time.
Psychological Factors Influencing Pain
Fear and Avoidance
The fear-avoidance model suggests that fear of re-injury can lead to avoidance behaviors that hinder recovery and contribute to chronic pain. While fear and avoidance are natural responses to protect oneself, excessive avoidance can weaken muscles, decrease physical function, and negatively affect mental health.
Emotions, Mood, and Mental Health
Pain, particularly chronic pain, can significantly impact emotions, mood, and mental health. Feelings of anger, worry, sadness, guilt, hopelessness, frustration, depression, and anxiety are common. Conversely, these factors can also influence pain perception. The brain regions involved in emotions, mood, and mental health conditions overlap with those involved in pain processing. Co-occurring mental health conditions, such as depression, anxiety, PTSD, and sleep problems, are common in individuals with chronic pain. Addressing these psychological factors can improve chronic pain symptoms.
Resilience
Resilience, the ability to adapt and bounce back from life’s challenges, is crucial for managing chronic pain. It involves utilizing personal strengths, such as social support, problem-solving skills, humor, coping strategies, and enjoyable activities, to adapt to the challenges of living with pain. Resilience is not an innate trait but can be developed and strengthened through support and practice.
Beliefs and Thoughts About Pain
Beliefs and thoughts about pain significantly affect a person’s experience. Common unhelpful thinking styles associated with chronic pain include:
- Ongoing concerns about pain: Persistent worries about the future and the unknown aspects of pain.
- “Should” statements: Setting unrealistic expectations and feeling frustrated when unable to meet them.
- Self-blame: Attributing blame to oneself for triggering the pain.
These thinking styles can lead to negative emotions and exacerbate pain symptoms. Identifying and modifying unhelpful pain beliefs can improve chronic pain management.
Social Factors and the Social Determinants of Health
Social determinants of health, encompassing the environmental conditions where people live, learn, work, and play, influence health outcomes, including pain. These factors include economic stability, access to education and healthcare, safe neighborhoods, and strong social relationships. Research in this area is ongoing and aims to address disparities in pain and pain care.
Diagnosing and Treating Pain
Diagnosing Pain
Pain is a subjective experience, and self-reporting is crucial for diagnosis. Healthcare providers gather information about a patient’s pain history and perform physical examinations, neurological assessments, and diagnostic tests to identify potential underlying causes.
Diagnostic tools include:
- Physical and neurological examinations: Assessing movement, reflexes, sensation, balance, and coordination.
- Laboratory tests: Detecting infections, cancer, nutritional deficiencies, or hormonal imbalances.
- Imaging: Visualizing internal structures and tissues.
- Electrodiagnostic procedures: Assessing nerve function.
- Psychological assessments: Identifying psychological factors contributing to pain.
Treating Pain
The goal of pain management is to improve quality of life and function. Treatment options vary depending on the type of pain, its duration, and individual needs. The biopsychosocial approach is considered the best approach to prevent, assess, and treat chronic pain. This approach involves an interdisciplinary team of healthcare specialists, including pain management specialists, nurses, mental healthcare providers, physical or occupational therapists, complementary or integrative healthcare providers, and social workers.
While not all pain is curable, all pain can be managed. Common pain management strategies include:
- Medications: Analgesics, NSAIDs, opioids, antiseizure medications, antidepressants, muscle relaxants, and topical creams.
- Medical procedures and devices: Electrical stimulation (TENS, peripheral nerve stimulation, spinal cord stimulation), injections (steroid injections, botulinum toxin, trigger point injections), nerve blocks, radiofrequency ablation, and surgery.
- Behavioral medicine and physical therapy: Biofeedback, cognitive-behavioral therapy, counseling, and physical therapy.
- Lifestyle changes: Anti-inflammatory diets and exercise.
- Complementary and integrative health: Acupuncture, chiropractic care, massage therapy, and tai chi.
These treatments are often combined to optimize care for an individual.
Latest Updates on Pain Research
The National Institutes of Health (NIH) is actively involved in pain research, focusing on understanding pain mechanisms, developing new therapies, and addressing the opioid crisis. The NIH HEAL Initiative® aims to improve prevention and treatment strategies for opioid use disorder and enhance pain management. The Brain Research Through Advancing Innovative Neurotechnologies® (BRAIN) Initiative® explores ways to modulate neural circuitry to reduce pain.
Resources for Patients
Numerous organizations and resources provide information and support for individuals living with pain, including the American Academy of Family Physicians, the American Chronic Pain Association, the Arthritis Foundation, and the National Headache Foundation.
Improving Pain Care Through Research
Participating in clinical trials can contribute to advancing our understanding of pain and improving care. Clinical trials need participants of all ages, sexes, races, and ethnicities. For information about participating in clinical research visit NIH Clinical Research Trials and You. Learn about clinical trials currently looking for people with pain at Clinicaltrials.gov.
