Changes in the sexual desires of any partner in a sexual relationship, if sustained and unresolved, may cause problems in the relationship. The infidelity of a partner may be an indication that a partners changing sexual desires can no longer be satisfied within the current relationship. Problems can arise from disparity of sexual desires between partners, or poor communication between partners of sexual needs and preferences.There is no widely accepted measure of what is a healthy level for sex desire. Some people want to have sex every day, or more than once a day; others once a year or not at all. However, 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. Psychological perspectives
Psychoanalysis
Sigmund Freud, who is considered the originator of the modern use of the term, defined libido as "the energy, regarded as a quantitative magnitude... of those instincts which have to do with all that may be comprised under the word love." It is the instinctual energy or force, contained in what Freud called the id, the strictly unconscious structure of the psyche.
Isotretinoin and many SSRIs can cause a long-term decrease in libido and other sexual functions, even after users of those drugs have shown improvement in their depression and have stopped usage. Multiple studies have shown that with the exception of bupropion (Wellbutrin), trazodone (Desyrel) and nefazodone (Serzone), antidepressants generally will lead to lowered libido. SSRIs that typically lead to decreased libido are fluoxetine (Prozac), paroxetine (Paxil), fluvoxamine (Luvox), citalopram (Celexa) and sertraline (Zoloft). Some antidepressant users have tried decreasing their dosage in the hopes of maintaining an adequate sex drive. Other users try enrolling in psychotherapy to solve depression-related issues of libido. However, the effectiveness of this therapy is mixed, with many reporting that it had no or little effect on sexual drive.Testosterone is one of the hormones controlling libido in human beings. Emerging research is showing that hormonal contraception methods like oral contraceptive pills (which rely on estrogen and progesterone together) are causing low libido in females by elevating levels of sex hormone-binding globulin (SHBG). SHBG binds to sex hormones, including testosterone, rendering them unavailable. Research is showing that even after ending a hormonal contraceptive method, SHBG levels remain elevated and no reliable data exists to predict when this phenomenon will diminish.Oral contraceptives lower androgen levels in users, and lowered androgen levels generally lead to a decrease in sexual desire. However, usage of oral contraceptives has shown to typically not have a connection with lowered libido in women.