While common definitions of loneliness describe it as a state of solitude or being alone, loneliness is actually a state of mind. Loneliness causes people to feel empty, alone and unwanted. People who are lonely often crave human contact, but their state of mind makes it more difficult to form connections with other people.

Loneliness, according to many experts, is not necessarily about being alone. Instead, it is the perception of being alone and isolated that matters most. For example, a college freshmen might feel lonely despite being surrounded by roommates and other peers. A soldier beginning his military career might feel lonely after being deployed to a foreign country, despite being constantly surrounded by other people.
What Causes Loneliness?

According to research by John Cacioppo, a University of Chicago psychologist and one of the top loneliness experts, loneliness is strongly connected to genetics. Other contributing factors include situational variables, such as physical isolation, moving to a new location and divorce. The death of someone significant in a person's life can also lead to feelings of loneliness. Loneliness can also be a symptom of a psychological disorder such as depression.

Loneliness can also be attributed to internal factors such as low self-esteem. People who lack confidence in themselves often believe that they are unworthy of the attention or regard of other people. This can lead to isolation and chronic loneliness.
The Health Consequences of Loneliness

Loneliness has a wide range of negative effects on both physical and mental health. Some of the the health risks associated with loneliness include:2

Depression and suicide
Cardiovascular disease and stroke
Increased stress levels
Decreased memory and learning
Antisocial behavior
Poor decision-making
Alcoholism and drug abuse
The progression of Alzheimer's disease
Altered brain function

Research has shown that loneliness can impact stress, heart health and immunity. But these are not the only areas in which loneliness takes its toll. "Lonely adults consume more alcohol and get less exercise than those who are not lonely," explained John Cacioppo, co-author of the book Loneliness: Human Nature and the Need for Social Connection in an interview with U.S. News and World Report. "Their diet is higher in fat, their sleep is less efficient, and they report more daytime fatigue. Loneliness also disrupts the regulation of cellular processes deep within the body, predisposing us to premature aging."

Researchers have found that low levels of loneliness are associated with marriage, higher income and higher educational status. High levels of loneliness are associated with physical health symptoms, living alone, small social networks and low quality social relationships.
The Symptoms of Loneliness

Researchers also suggest that loneliness is becoming more common in the United States. When polled as part of a 1984 questionnaire, respondents most frequently reported having three close confidants. When the question was asked again in 2004, the most common response was zero confidants. This trend is unfortunate, since experts believe that it is not the quantity of social interaction that combats loneliness, but that it is the quality. Having just three or four close friends is enough to ward off loneliness and reduce the negative health consequences associated with this state of mind.
Loneliness Can Be Contagious
One study by Cacioppo suggests that loneliness may actually be contagious. In a ten-year study, researchers examined how loneliness spreads in social networks. The results indicated that people close to someone experiencing loneliness were 52-percent more likely to become lonely as well.

Treating and Preventing Loneliness

John Cacioppo offers a few tips on how to overcome loneliness:

Recognize that loneliness is a sign that something needs to change.

Understand the effects that loneliness has on your life, both physically and mentally.

Consider doing community service or another activity that you enjoy. These situations present great opportunities to meet people and cultivate new friendships and social interactions.

Focus on developing quality relationships with people who share similar attitudes, interests and values with you.

Expect the best. Lonely people often expect rejection, so instead focus on positive thoughts and attitudes in your social relationships.