Libido refers to a person's sex drive or desire for sexual activity. The desire for sex is an aspect of a person's sexuality, but varies enormously from one person to another, and it also varies depending on circumstances at a particular time. A person who has extremely frequent or a suddenly increased sex drive may be experiencing hypersexuality. Sex drive has usually biological, psychological, and social components. Biologically, hormone levels, such as testosterone, is believed to affect sex drive; social factors, such as work and family, also have an impact; as do internal psychological factors, like personality and stress. Sex drive may be affected by medical conditions, medications, lifestyle and relationship issues.
There is no necessary correlation between the desire for sex and actual sexual activity. For example, a person may have a desire for sex but not have the opportunity to act on that desire, or may on moral or religious reasons refrain from acting on the urge. Psychologically, a person's urge can be repressed or sublimated. On the other hand, a person can engage in sexual activity without an actual desire for it. There is no measure of what is a healthy level for sex. Some people have sex (or feel like having it) every day (or more than once a day), others once a year or not at all.
The concept of libido was first introduced by Sigmund Freud as the instinct energy or force, contained in what Freud called the id. Carl Jung defined libido as the free creative or psychic energy an individual has to put toward personal development or individuation. Within the category of sexual behavior, libido would fall under the appetitive phase wherein an individual will usually undergo certain behaviors in order to gain access to a mate.
A person who lacks a desire for sexual activity for some period of time may be experiencing a hypoactive sexual desire disorder or may be asexual. A sexual desire disorder is more common in women, but rare in men. Erectile dysfunction is more common in men and may be a cause for the lack of sexual desire, but with which it should not be confused. Moreover, specialists have brought to attention that libido impairment may not even occur in cases of men with erectile dysfunction. However, men can also experience a decrease in their libido as they age.
The American Medical Association has estimated that several million US women suffer from a female sexual arousal disorder. Some specialists claim that women may experience low libido due to some hormonal abnormalities such as lack of luteinising hormone or androgenic hormones, although these theories are still controversial. Also, women commonly lack sexual desire in the period immediately after birth. Moreover, any condition affecting the genital area can make women reject the idea of having intercourse. It has been estimated that half of women experience different health problems in the area of the vagina and vulva, such as thinning, tightening, dryness or atrophy. Frustration may appear as a result of these issues and because many of them lead to painful sexual intercourse, many women prefer not having sex at all. Surgery or major health conditions such as arthritis, cancer, diabetes, high blood pressure, coronary artery disease or infertility may have the same effect in women. Common surgeries that affect the hormonal levels in women include hysterectomies.
Although some specialists disagree with this theory, menopause is still considered by the majority a factor that can cause decreased sex desire in women. The levels of estrogen decrease at menopause and this usually causes a lower interest in sex and vaginal dryness which makes intercourse painful. Also, the levels of testosterone decrease at menopause and this is why some women may experience a contrary effect, of an increased libido. Birth control pills may also influence the libido of women, generally by decreasing it.