Illness
Encyclopedia
Illness is a state of poor health
. Illness is sometimes considered another word for disease
. Others maintain that fine distinctions exist. Some have described illness as the subjective perception by a patient of an objectively defined disease.
, " [...] a state of complete physical, mental and social well-being and not merely the absence of disease
or infirmity". When these conditions are not fulfilled, then one can be considered to have an illness or be ill. Medication and the science of pharmacology
is used to cure or reduce symptoms of an illness or medical conditions. Developmental disability
is a term used to describe severe, life-long disabilities attributable to mental and/or physical impairments.
or mind
that cause pain
, dysfunction
, or distress to the person afflicted or those in contact with the person can be deemed an illness. Sometimes the term is used broadly to include injuries, disabilities, syndrome
s, infections, symptom
s, deviant behaviors, and atypical variations of structure and function, while in other contexts these may be considered distinguishable categories. A pathogen
or infectious agent is a biological agent that causes disease or illness to its host. A passenger virus
is a virus that simply hitchhikes in the body of a person or infects the body without causing symptoms, illness or disease. Foodborne illness
or food poisoning is any illness resulting from the consumption of food contaminated with pathogenic bacteria, toxins, viruses, prions or parasites.
, much illness is not directly caused by an infection
or body dysfunction but is instead a response created by the body. Fever
, for example, is not caused directly by bacteria or viruses but by the body raising its normal human body temperature
, which some people believe inhibits the growth of the infectious organism. Evolutionary medicine calls this set of responses sickness behavior
.Hart, B. L. (1988) "Biological basis of the behavior of sick animals". Neurosci Biobehav Rev. 12: 123-137. PMID 3050629 Johnson, R. (2002) "The concept of sickness behavior: a brief chronological account of four key discoveries". Veterinary Immunology and Immunopathology. 87: 443-450 PMID 12072271 These include such illness defining health changes as lethargy, depression
, anorexia
, sleepiness, hyperalgesia
, and the inability to concentrate
. These together with fever are caused by the brain through its top down control
upon the body. They are, therefore, not necessary, and often do not accompany an infection (such as the lack of fever during malnutrition
or late pregnancy
) when they have a cost
that outweighs their benefit. In humans, an important factor are beliefs that influence whether the health management system
in the brain that evaluates costs and benefits deploys them or not. The health management system, when it factors in false information, has been suggested to underlie the placebo
reduction of illness.
(or Emotional disability, Cognitive dysfunction) is a broad generic label for a category of illnesses that may include affective or emotional
instability, behavioral dysregulation, and/or cognitive dysfunction or impairment. Specific illnesses known as mental illnesses include major depression, generalized anxiety disorder, schizophrenia
, and attention deficit hyperactivity disorder, to name a few. Mental illness can be of biological (e.g., anatomical, chemical, or genetic) or psychological (e.g., trauma or conflict) origin. It can impact one’s ability to work or go to school and contribute to problems in relationships. Other generic names for mental illness include “mental disorder”, “psychiatric disorder”, “psychological disorder”,“abnormal psychology”, “emotional disability”, “emotional problems”, or “behavior problem”. The term insanity
is used technically as a legal term. Brain damage
may result in impairment of mental function.
is the scientific study of factors affecting the health and illness of individuals and populations, and serves as the foundation and logic of interventions made in the interest of public health and preventive medicine.
Behavioral medicine
is an interdisciplinary field of medicine concerned with the development and integration of psychosocial, behavioral and biomedical knowledge relevant to health and illness. Clinical Global Impression
scale to assess treatment response in patients with mental disorders. It's " Improvement scale" requires the clinician to rate how much the patient's illness has improved or worsened relative to a baseline state. Mental confusion
and decreased alertness may indicate that a chronic illness has gotten worse.
Health
Health is the level of functional or metabolic efficiency of a living being. In humans, it is the general condition of a person's mind, body and spirit, usually meaning to be free from illness, injury or pain...
. Illness is sometimes considered another word for disease
Disease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...
. Others maintain that fine distinctions exist. Some have described illness as the subjective perception by a patient of an objectively defined disease.
Introduction
The mode of being healthy includes, as defined by the World Health OrganizationWorld Health Organization
The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...
, " [...] a state of complete physical, mental and social well-being and not merely the absence of disease
Disease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...
or infirmity". When these conditions are not fulfilled, then one can be considered to have an illness or be ill. Medication and the science of pharmacology
Pharmacology
Pharmacology is the branch of medicine and biology concerned with the study of drug action. More specifically, it is the study of the interactions that occur between a living organism and chemicals that affect normal or abnormal biochemical function...
is used to cure or reduce symptoms of an illness or medical conditions. Developmental disability
Developmental disability
Developmental disability is a term used in the United States and Canada to describe lifelong disabilities attributable to mental or physical impairments, manifested prior to age 18. It is not synonymous with "developmental delay" which is often a consequence of a temporary illness or trauma during...
is a term used to describe severe, life-long disabilities attributable to mental and/or physical impairments.
Physical
Conditions of the bodyHuman body
The human body is the entire structure of a human organism, and consists of a head, neck, torso, two arms and two legs.By the time the human reaches adulthood, the body consists of close to 100 trillion cells, the basic unit of life...
or mind
Mind
The concept of mind is understood in many different ways by many different traditions, ranging from panpsychism and animism to traditional and organized religious views, as well as secular and materialist philosophies. Most agree that minds are constituted by conscious experience and intelligent...
that cause pain
Pain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
, dysfunction
Dysfunction
Dysfunction can refer to:* Abnormality * Dysfunctional family* Sexual dysfunction* Dysfunction , an album by the rock band Staind...
, or distress to the person afflicted or those in contact with the person can be deemed an illness. Sometimes the term is used broadly to include injuries, disabilities, syndrome
Syndrome
In medicine and psychology, a syndrome is the association of several clinically recognizable features, signs , symptoms , phenomena or characteristics that often occur together, so that the presence of one or more features alerts the physician to the possible presence of the others...
s, infections, symptom
Symptom
A symptom is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality...
s, deviant behaviors, and atypical variations of structure and function, while in other contexts these may be considered distinguishable categories. A pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...
or infectious agent is a biological agent that causes disease or illness to its host. A passenger virus
Passenger virus
A passenger virus is a virus that is frequently found in samples from diseased tissue, such as tumours, but does not contribute to causing the disease.-Experimental demonstration of passenger status:Proving that a virus has no causative role can be difficult...
is a virus that simply hitchhikes in the body of a person or infects the body without causing symptoms, illness or disease. Foodborne illness
Foodborne illness
Foodborne illness is any illness resulting from the consumption of contaminated food, pathogenic bacteria, viruses, or parasites that contaminate food, as well as chemical or natural toxins such as poisonous mushrooms.-Causes:Foodborne illness usually arises from improper handling, preparation, or...
or food poisoning is any illness resulting from the consumption of food contaminated with pathogenic bacteria, toxins, viruses, prions or parasites.
Adaptive response
According to evolutionary medicineEvolutionary medicine
Evolutionary medicine or Darwinian medicine is the application of modern evolutionary theory to understanding health and disease. It provides a complementary scientific approach to the present mechanistic explanations that dominate medical science, and particularly modern medical education...
, much illness is not directly caused by an infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
or body dysfunction but is instead a response created by the body. Fever
Fever
Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...
, for example, is not caused directly by bacteria or viruses but by the body raising its normal human body temperature
Normal human body temperature
Normal human body temperature, also known as normothermia or euthermia, is a concept that depends upon the place in the body at which the measurement is made, and the time of day and level of activity of the person...
, which some people believe inhibits the growth of the infectious organism. Evolutionary medicine calls this set of responses sickness behavior
Sickness behavior
thumb|350px|right|[[Michael Peter Ancher|Ancher, Michael]], "The Sick Girl", 1882, [[Statens Museum for Kunst]]Sickness behavior is a coordinated set of adaptive behavioral changes that develop in ill individuals during the course of an infection....
.Hart, B. L. (1988) "Biological basis of the behavior of sick animals". Neurosci Biobehav Rev. 12: 123-137. PMID 3050629 Johnson, R. (2002) "The concept of sickness behavior: a brief chronological account of four key discoveries". Veterinary Immunology and Immunopathology. 87: 443-450 PMID 12072271 These include such illness defining health changes as lethargy, depression
Depression (mood)
Depression is a state of low mood and aversion to activity that can affect a person's thoughts, behaviour, feelings and physical well-being. Depressed people may feel sad, anxious, empty, hopeless, helpless, worthless, guilty, irritable, or restless...
, anorexia
Anorexia (symptom)
Anorexia is the decreased sensation of appetite...
, sleepiness, hyperalgesia
Hyperalgesia
Hyperalgesia is an increased sensitivity to pain, which may be caused by damage to nociceptors or peripheral nerves. Temporary increased sensitivity to pain also occurs as part of sickness behavior, the evolved response to infection.-Types:...
, and the inability to concentrate
Attention
Attention is the cognitive process of paying attention to one aspect of the environment while ignoring others. Attention is one of the most intensely studied topics within psychology and cognitive neuroscience....
. These together with fever are caused by the brain through its top down control
Neural top down control of physiology
Neural top down control of physiology concerns the direct regulation by the brain of physiological functions...
upon the body. They are, therefore, not necessary, and often do not accompany an infection (such as the lack of fever during malnutrition
Malnutrition
Malnutrition is the condition that results from taking an unbalanced diet in which certain nutrients are lacking, in excess , or in the wrong proportions....
or late pregnancy
Pregnancy
Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...
) when they have a cost
Deployment cost-benefit selection in physiology
Deployment cost–benefit selection in physiology concerns the costs and benefits of physiological process that can be deployed and selected in regard to whether they will increase or not an animal’s survival and biological fitness...
that outweighs their benefit. In humans, an important factor are beliefs that influence whether the health management system
Health management system
The health management system is an evolutionary medicine regulative process proposed by Nicholas Humphrey in which actuarial assessment of fitness and economic-type cost-benefit analysis determines the body’s regulation of its physiology and health...
in the brain that evaluates costs and benefits deploys them or not. The health management system, when it factors in false information, has been suggested to underlie the placebo
Placebo
A placebo is a simulated or otherwise medically ineffectual treatment for a disease or other medical condition intended to deceive the recipient...
reduction of illness.
Mental
Mental illnessMental illness
A mental disorder or mental illness is a psychological or behavioral pattern generally associated with subjective distress or disability that occurs in an individual, and which is not a part of normal development or culture. Such a disorder may consist of a combination of affective, behavioural,...
(or Emotional disability, Cognitive dysfunction) is a broad generic label for a category of illnesses that may include affective or emotional
Emotion
Emotion is a complex psychophysiological experience of an individual's state of mind as interacting with biochemical and environmental influences. In humans, emotion fundamentally involves "physiological arousal, expressive behaviors, and conscious experience." Emotion is associated with mood,...
instability, behavioral dysregulation, and/or cognitive dysfunction or impairment. Specific illnesses known as mental illnesses include major depression, generalized anxiety disorder, schizophrenia
Schizophrenia
Schizophrenia is a mental disorder characterized by a disintegration of thought processes and of emotional responsiveness. It most commonly manifests itself as auditory hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking, and it is accompanied by significant social...
, and attention deficit hyperactivity disorder, to name a few. Mental illness can be of biological (e.g., anatomical, chemical, or genetic) or psychological (e.g., trauma or conflict) origin. It can impact one’s ability to work or go to school and contribute to problems in relationships. Other generic names for mental illness include “mental disorder”, “psychiatric disorder”, “psychological disorder”,“abnormal psychology”, “emotional disability”, “emotional problems”, or “behavior problem”. The term insanity
Insanity
Insanity, craziness or madness is a spectrum of behaviors characterized by certain abnormal mental or behavioral patterns. Insanity may manifest as violations of societal norms, including becoming a danger to themselves and others, though not all such acts are considered insanity...
is used technically as a legal term. Brain damage
Brain damage
"Brain damage" or "brain injury" is the destruction or degeneration of brain cells. Brain injuries occur due to a wide range of internal and external factors...
may result in impairment of mental function.
Study of illness
EpidemiologyEpidemiology
Epidemiology is the study of health-event, health-characteristic, or health-determinant patterns in a population. It is the cornerstone method of public health research, and helps inform policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive...
is the scientific study of factors affecting the health and illness of individuals and populations, and serves as the foundation and logic of interventions made in the interest of public health and preventive medicine.
Behavioral medicine
Behavioral medicine
Behavioral medicine is an interdisciplinary field of medicine concerned with the development and integration of knowledge in the biological, behavioral, psychological, and social sciences relevant to health and illness...
is an interdisciplinary field of medicine concerned with the development and integration of psychosocial, behavioral and biomedical knowledge relevant to health and illness. Clinical Global Impression
Clinical Global Impression
The Clinical Global Impression rating scales are commonly used measures of symptom severity, treatment response and the efficacy of treatments in treatment studies of patients with mental disorders...
scale to assess treatment response in patients with mental disorders. It's " Improvement scale" requires the clinician to rate how much the patient's illness has improved or worsened relative to a baseline state. Mental confusion
Mental confusion
Confusion of a pathological degree usually refers to loss of orientation sometimes accompanied by disordered consciousness and often memory Confusion (from Latin confusĭo, -ōnis, noun of action from confundere "to pour together", also "to confuse") of a pathological degree usually refers to loss...
and decreased alertness may indicate that a chronic illness has gotten worse.
See also
- ConvalescenceConvalescenceConvalescence is the gradual recovery and of health and strength after illness. It refers to the later stage of an infectious disease or illness when the patient recovers and returns to normal, but may continue to be a source of infection even if feeling better...
- Wellness (alternative medicine)Wellness (alternative medicine)Wellness is generally used to mean a healthy balance of the mind, body and spirit that results in an overall feeling of well-being. It has been used in the context of alternative medicine since Halbert L. Dunn, M.D., began using the phrase high level wellness in the 1950s...
is used to mean a healthy balance of the mind-body and spirit that results in an overall feeling of well-being. - Sickness behaviorSickness behaviorthumb|350px|right|[[Michael Peter Ancher|Ancher, Michael]], "The Sick Girl", 1882, [[Statens Museum for Kunst]]Sickness behavior is a coordinated set of adaptive behavioral changes that develop in ill individuals during the course of an infection....