If a decrease in a person's sexual interest, desire, and fantasies causes significant personal distress or difficulties in the couple's relationship, we call this decreased sexual desire disorder. Decreased sexual desire disorder is the most common reason for psychiatric referrals among sexual problems and is seen in 50% of couples seeking sexual therapy. Almost half of the couples who present with decreased sexual desire and arousal disorder also have another co-occurring sexual dysfunction problem. It is estimated that 20% of the entire population has decreased sexual desire disorder.

Misinformation about sex, paid sex work, myths about male sexuality, unconscious sexual fears, guilt, and unresolved conflicts all contribute to the development of the disorder.

Patients with decreased sexual desire disorder exhibit very few or no thoughts or fantasies about sex, a reduced response to sexually suggestive stimuli, and little interest in initiating sexual experiences.

Sometimes, decreased sexual desire can be used to mask another sexual dysfunction. For example, a man with erectile dysfunction might perceive it as a failure and avoid sex. Or, in some cases, sexuality is experienced only through masturbation, with a decrease in interest in the partner. The reason may be relationship problems with the partner, unshared fantasies, or other individual problems. Sexuality is a self-reinforcing cycle. As the frequency of sexual intercourse decreases, sexual urges are suppressed, and the frequency of intercourse decreases even further. In other words, as frequency increases, desire increases and intercourse becomes more frequent; as frequency decreases, desire decreases and intercourse becomes less frequent.

Most studies show that sexual desire decreases with age in both women and men. Interestingly, however, the degree to which people complain about decreased sexual desire also decreases with age.

Sexual interest and arousal disorders can also develop as a result of chronic stress, anxiety, or depression. Sexual desire can also be affected by the intimacy and distance, ups and downs, in a couple's relationship. Men generally view sexual intercourse as a way to establish emotional closeness with their partner, while women perceive sexual intercourse as a result of emotional closeness.

Problems with sexual interest and arousal can simply be a form of revenge or punishment, or a sign that the relationship is deteriorating. Many women experiencing sexual interest and arousal disorders also have marital problems. In such cases, couples therapy can be effective in resolving the issue. However, sexual dysfunction (including decreased libido) can occur even without significant problems in marital harmony.

Sexual interest and arousal disorders can reduce the frequency of sexual intercourse in both men and women, or transform sex into a personal ordeal performed solely to please the partner. There is no such thing as a "normal" frequency of sexual intercourse. As I mentioned at the beginning, anything can be considered normal as long as it doesn't cause personal or relationship distress. The key here is the couple's compatibility. There's no set frequency for sexual intercourse as long as it genuinely brings happiness, not just as a tolerant gesture, a temporary fix, or out of obligation. If it's not a source of complaint for the individual or their partner, it's not considered a disorder.

Many factors influence the frequency of sexual activity (I say activity instead of intercourse because masturbation is also a natural way to experience sexuality): the presence of a suitable partner, self-confidence, previous sexual experiences, age, demanding work schedule, stress, pregnancy, the duration and status of the relationship, child planning and the use of birth control methods, losses, medication side effects, acute or chronic illnesses, and cultural and environmental factors/beliefs.

Because decreased sexual desire can stem from a wide variety of causes, a thorough evaluation is needed before beginning sexual therapy. In some cases, urology and internal medicine examinations may also be necessary. Furthermore, if decreased sexual desire is a result of a failing relationship, couples therapy may be required before sexual therapy.