Loneliness
Loneliness  is a feeling where people experience a powerful surge of emptiness and solitude. Loneliness is more than the feeling of wanting company or wanting to do something with another person. Someone who is lonely may find it hard to form human contact.
One of the first recorded uses of the word "lonely" was in William Shakespeare's Coriolanus, Act IV Scene 1.

# Distinction from solitude
Loneliness is not the same as being alone. Many people have times when they are alone through circumstances or choice. Being alone can be experienced as positive, pleasurable, and emotionally refreshing if it is under the individual's control. Solitude is the state of being alone and secluded from other people, and often implies having made a conscious choice to be alone. Loneliness does not require aloneness and is often experienced even in crowded places.  It can be described as the absence of identifaction, understanding or compassion.
In their growth as individuals, humans start a separation process at birth, which continues with growing independence towards adulthood. As such, feeling alone can be a healthy emotion and, indeed, choosing to be alone for a period of solitude can be enriching. To experience loneliness, however, can be to feel overwhelmed by an unbearable feeling of separateness at a profound level. This can manifest in feelings of abandonment, rejection, depression, insecurity, anxiety, hopelessness, unworthiness, meaninglessness, and resentment. If these feelings are prolonged they may become debilitating and prevent the affected individual from developing healthy relationships and lifestyles. If the individual is convinced he or she is unlovable, this will increase the experience of suffering and the likelihood of avoiding social contact. Low self-esteem will often trigger the social disconnection which can lead to loneliness.
In some people, temporary or prolonged loneliness can lead to notable artistic and creative expression, for example, as was the case with Emily Dickinson. This is not to imply that loneliness itself ensures this creativity; rather, it may have an influence on the subject matter of the artist.

# Common causes
People can experience loneliness for many reasons, and many life events are associated with it. The lack of friendship relations during childhood and adolescence, or the physical absence of meaningful people around a person are causes for loneliness, depression, and involuntary celibacy. At the same time loneliness may be a symptom of another social or psychological problem (for example chronic depression) which should be analyzed.
Many people experience loneliness for the first time when they are left alone as an infant. It is also a very common though normally temporary consequence of divorce or the breakup or loss of any important long-term relationship. In these cases, it may stem both from the loss of a specific person and from the withdrawal from social circles caused by the event or the associated sadness.
Loss of a significant person in one's life will typically initiate a grief response; here, one might feel lonely, even in the company of others. Loneliness may also occur after the birth of a child, after marriage or any socially disruptive event, such as moving from one's home town to a university campus. Loneliness can occur within marriages or similar close relationships where there is anger, resentment, or where love cannot be given or received. It may represent a dysfunction of communication. Learning to cope with changes in life patterns is essential in overcoming loneliness.

# Typology

## Common types
Loneliness can be summarized as falling into these categories:
- Situational / circumstantial - loss of a relationship, move to a new city
- Developmental - a need for intimacy balanced by a need for individualism
- Internal - often including feelings of low self-esteem and vulnerability

## Common symptoms
Loneliness can evoke feelings that 'everyone else' has friends, or that one is socially inadequate and socially unskilled. A lonely person may become convinced there is something wrong with him or her, or that no one understands his or her situation. Such a person may feel reluctant to attempt to change or to try new things. In extreme cases, a person may feel a sense of emptiness, which may become a state of clinical depression.

# In modern society
Loneliness frequently occurs in heavily populated cities; in these cities many people feel utterly alone and cut off, even when surrounded by throngs of other people. They experience a loss of identifiable community in an anonymous crowd. It is unclear whether loneliness is a condition aggravated by high population density itself, or simply part of the human condition brought on by this social milieu. Certainly, loneliness occurs even in societies with much smaller populations, but the sheer number of random people that one comes into contact with daily in a city, even if only briefly, may raise barriers to actually interacting more deeply with them and increase the feeling of being cut off and alone. Quantity of contact does not translate into quality of contact.
Loneliness appears to have become particularly prevalent in modern times. At the beginning of the last century families were typically larger and more stable, divorce was rarer and relatively few people lived alone. Today, the trend has reversed direction: over a quarter of the U.S. population lived alone in 1998. In 1995, 24 million Americans lived in single-person households; by 2010, it is estimated that number will have increased to around 31 million.
A 2006 study in the American Sociological Review found that Americans on average had only two close friends to confide in, down from an average of three in 1985.  The percentage of people who noted having no such confidant rose from 10 percent to almost 25 percent; and 19 additional percent said they had only a single confidant (often their spouse), raising the risk of serious loneliness in case the relationship ended.

# As human condition
The existentialist school of thought views loneliness as the essence of being human. Each human being comes into the world alone, travels through life as a separate person, and ultimately dies alone. Coping with this, accepting it, and learning how to direct our own lives with some degree of grace and satisfaction is the human condition..  Some philosophers, such as Sartre, believe in a epistemic loneliness in which loneliness is a fundamental part of the human condition because of the paradox between the desire of man's consciousness to have meaning met with the isolation and nothingness of the universe. However, other existentialist thinkers argue the opposite. Human beings might be said to actively "engage" each other and the universe as they communicate and create, and loneliness is merely the feeling of being cut off from this process.

# Effects
Chronic loneliness (as opposed to the normal loneliness everyone feels from time to time), is a serious, life-threatening condition. At least one study has empirically correlated it with an increased risk of cancer, especially for those who hide their loneliness from the outside world. It is associated with increased risk of stroke and cardiovascular disease. People who are socially isolated also report poor sleep quality and thus have diminished restorative processes. Loneliness is also linked with depression, a risk factor for suicide. Emile Durkheim also described loneliness, specifically the inability or unwillingness to live for others (i.e. for friendships or altruistic ideas), as the main reason for what he called "egoistic" suicide.
Loneliness can play a part in alcoholism. In children, a lack of social connections is directly linked to several forms of antisocial and self-destructive behavior, most notably hostile and delinquent behavior. In both children and adults, loneliness often has a negative impact on learning and memory. Its effect on sleep patterns, as well as the above-mentioned other effects can have a devastating effect on the ability to function in everyday life.
Some other effects may not be symptomatic for years. In 2005, results from the U.S. Framingham Heart Study demonstrated that lonely men had raised levels of IL-6, a blood chemical linked to heart disease. A 2006 study conducted by the Center for Cognitive and Social Neuroscience at the University of Chicago found loneliness can add 30 points to a blood pressure reading for adults over the age of 50. Another remarkable finding, from a survey conducted by John Cacioppo, a psychologist at the University of Chicago, is that doctors say they provide better medical care to patients who have a strong network of family and friends than they do to patients who are alone.
Cacioppo's 2008 book, Loneliness: Human Nature and the Need for Social Connection, outlines five distinct pathways through which social isolation contributes to increased illness and early death.  He also offers an evolutionary rationale for why the subjective sense of social isolationlonelinessis so profoundly disruptive to human physiology that it impairs cognition and will power, alters DNA transcription in immune cells, and leads over time to high blood pressure.
Enforced loneliness (solitary confinement) has been a punishment method throughout history. It is often considered a form of tortureTemplate:Bywhom.

# Treatments
There are many different ways used to treat loneliness or clinical depression. The first step that most doctors recommend to patients is therapy. Therapy is a common and effective way of treating loneliness and is often successful. Short term therapy, the most common form for lonely or depressed patients, typically occurs over a period of 10 to 20 weeks. During therapy, emphasis is put on understanding the cause of the problem; reversing the negative thoughts, feelings, and attitudes resulting from the problem; and exploring ways to cure the patient. Some doctors also recommend group therapy as a means to connect with other sufferers and establish a support system. Doctors also frequently prescribe anti-depressants to patients as a stand-alone treatment or in conjunction with therapy. It usually takes a few tries before a patient finds the correct anti-depressant medication. Some patients may also develop a resistance to a certain type of medication and need to switch periodically.
Alternative approaches to treating depression are suggested by many doctors. These treatments may include exercise, dieting, hypnosis, electro-shock therapy, acupuncture, herbs, and many others. Many patients find that participating in these activities fully or partially alleviate symptoms related to depression. Another treatment for both loneliness and depression is pet therapy, or animal-assisted therapy, as it is more formally known. Some studies and surveys, as well as anecdotal evidence provided by volunteer and community organizations, indicate that the presence of animal companionsdogs, cats, and even rabbits or guinea pigscan ease feelings of depression and loneliness among some sufferers. According to the Centers for Disease Control, there are a number of health benefits associated with pet ownership. In addition to easing feelings of loneliness (because of the increased opportunities for socializing with other pet owners, beyond the companionship the animal provides), having a pet is associated with lowered blood pressure and decreased levels of cholesterol and triglycerides.