Libido

Libido is governed primarily by activity in the mesolimbic dopamine pathway (ventral tegmental area and nucleus accumbens).[1] Consequently, dopamine and related trace amines (primarily phenethylamine)[16] that modulate dopamine neurotransmission play a critical role in regulating libido.[1]

Other neurotransmitters, neuropeptides, and sex hormones that affect sex drive by modulating activity in or acting upon this pathway include:

Sex hormone levels and the menstrual cycle[edit]

A woman's desire for sex is correlated to her menstrual cycle, with many women experiencing a heightened sexual desire in the several days immediately before ovulation,[31] which is her peak fertility period, which normally occurs two days before until two days after the ovulation.[32] This cycle has been associated with changes in a woman's testosterone levels during the menstrual cycle. According to Gabrielle Lichterman, testosterone levels have a direct impact on a woman's interest in sex. According to her, testosterone levels rise gradually from about the 24th day of a woman's menstrual cycle until ovulation on about the 14th day of the next cycle, and during this period the woman's desire for sex increases consistently. The 13th day is generally the day with the highest testosterone levels. In the week following ovulation, the testosterone level is the lowest and as a result women will experience less interest in sex.[17][better source needed]

Also, during the week following ovulation, progesterone levels increase, resulting in a woman experiencing difficulty achieving orgasm. Although the last days of the menstrual cycle are marked by a constant testosterone level, women's libido may get a boost as a result of the thickening of the uterine lining which stimulates nerve endings and makes a woman feel aroused.[33] Also, during these days, estrogen levels decline, resulting in a decrease of natural lubrication.

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. However, the levels of testosterone increase at menopause and this may be why some women may experience a contrary effect of an increased libido.[citation needed]

Psychological and social factors[edit]

Certain psychological or social factors can reduce the desire for sex. These factors can include lack of privacy or intimacy, stress or fatigue, distraction or depression. Environmental stress, such as prolonged exposure to elevated sound levels or bright light, can also affect libido. Other causes include experience of sexual abuse, assault, trauma, or neglect, body image issues, and anxiety about engaging in sexual activity.[34]

Individuals with PTSD may find themselves with reduced sexual desire. Struggling to find pleasure, as well as having trust issues, many with PTSD experience feelings of vulnerability, rage and anger, and emotional shutdowns, which have been shown to inhibit sexual desire in those with PTSD.[35] Reduced sex drive may also be present in trauma victims due to issues arising in sexual function. For women, it has been found that treatment can improve sexual function, thus helping restore sexual desire.[36] Depression and libido decline often coincide, with reduced sex drive being one of the symptoms of depression.[37] Those suffering from depression often report the decline in libido to be far reaching and more noticeable than other symptoms.[37] In addition, those with depression often are reluctant to report their reduced sex drive, often normalizing it with cultural/social values, or by the failure of the physician to inquire about it.

Physical factors[edit]

Physical factors that can affect libido include endocrine issues such as hypothyroidism, the effect of certain prescription medications (for example flutamide), and the attractiveness and biological fitness of one's partner, among various other lifestyle factors.[38]

In males, the frequency of ejaculations affects the levels of serum testosterone, a hormone which promotes libido. A study of 28 males aged 21–45 found that all but one of them had a peak (145.7% of baseline [117.8%–197.3%]) in serum testosterone on the 7th day of abstinence from ejaculation.[39]

Anemia is a cause of lack of libido in women due to the loss of iron during the period.[40]

Smoking, alcohol abuse, and the use of certain drugs can also lead to a decreased libido.[citation needed] Moreover, specialists suggest that several lifestyle changes such as exercising, quitting smoking, lowering consumption of alcohol or using prescription drugs may help increase one's sexual desire.[citation needed]

Medications[edit]

Some people purposefully attempt to decrease their libido through the usage of anaphrodisiacs.[41] Aphrodisiacs, such as dopaminergic psychostimulants, are a class of drugs which can increase libido. On the other hand, a reduced libido is also often iatrogenic and can be caused by many medications, such as hormonal contraception, SSRIs and other antidepressants, antipsychotics, opioids and beta blockers.

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.[37][42] Multiple studies have shown that with the exception of bupropion (Wellbutrin), trazodone (Desyrel) and nefazodone (Serzone), antidepressants generally will lead to lowered libido.[37] SSRIs that typically lead to decreased libido are fluoxetine (Prozac), paroxetine (Paxil), fluvoxamine (Luvox), citalopram (Celexa) and sertraline (Zoloft).[37] There are several ways to try and reap the benefits of the antidepressants while maintaining high enough sex drive levels. Some antidepressant users have tried decreasing their dosage in the hopes of maintaining an adequate sex drive. Results of this are often positive, with both drug effectiveness not reduced and libido preserved. Other users try enrolling in psychotherapy to solve depression-related issues of libido. However, the effectiveness of this therapy is mixed, with lots reporting that it had no or little effect on sexual drive.[37]