|Classification and external resources|
Sexual dysfunction or sexual malfunction (see also sexual function) refers to a difficulty experienced by an individual or a couple during any stage of a normal sexual activity, including desire, arousal or orgasm.
Sexual desire disorders or decreased libido are characterised by a lack or absence for some period of time of sexual desire or libido for sexual activity or of sexual fantasies. The condition ranges from a general lack of sexual desire to a lack of sexual desire for the current partner. The condition may have started after a period of normal sexual functioning or the person may always have had no/low sexual desire.
The causes vary considerably, but include a possible decrease in the production of normal estrogen in women or testosterone in both men and women. Other causes may be aging, fatigue, pregnancy, medications (such as the SSRIs) or psychiatric conditions, such as depression and anxiety. Loss of libido from SSRIs usually reverses after SSRIs are discontinued, but in some cases it does not. This has been called PSSD; however, this is not a classification that would be found in any current medical text. While a number of causes for low sexual desire are often cited, only some of these have ever been the object of empirical research. Many rely entirely on the impressions of therapists.
Sexual arousal disorders were previously known as frigidity in women and impotence in men, though these have now been replaced with less judgmental terms. Impotence is now known as erectile dysfunction, and frigidity has been replaced with a number of terms describing specific problems with, for example, desire or arousal.
For both men and women, these conditions can manifest themselves as an aversion to, and avoidance of, sexual contact with a partner. In men, there may be partial or complete failure to attain or maintain an erection, or a lack of sexual excitement and pleasure in sexual activity.
There may be medical causes to these disorders, such as decreased blood flow or lack of vaginal lubrication. Chronic disease can also contribute, as well as the nature of the relationship between the partners. Unlike disorders of orgasm, as the success of Viagra (sildenafil citrate) attests, most erectile disorders in men are primarily physical conditions.
Erectile dysfunction or impotence is a sexual dysfunction characterized by the inability to develop or maintain an erection of the penis. There are various underlying causes, such as damage to the nervi erigentes which prevents or delays erection, or diabetes, which simply decreases blood flow to the tissue in the penis, many of which are medically reversible.
The causes of erectile dysfunction may be psychological or physical. Psychological impotence can often be helped by almost anything that the patient believes in; there is a very strong placebo effect. Physical damage is much more severe. One leading physical cause of ED is continual or severe damage taken to the nervi erigentes. These nerves course beside the prostate arising from the sacral plexus and can be damaged in prostatic and colo-rectal surgeries.
Due to its embarrassing nature and the shame felt by sufferers, the subject was taboo for a long time, and is the subject of many urban legends. Folk remedies have long been advocated, with some being advertised widely since the 1930s. The introduction of perhaps the first pharmacologically effective remedy for impotence, sildenafil (trade name Viagra), in the 1990s caused a wave of public attention, propelled in part by the news-worthiness of stories about it and heavy advertising.
Orgasm disorders are persistent delays or absence of orgasm following a normal sexual excitement phase. The disorder can have physical, psychological, or pharmacological origins. SSRI antidepressants are a common pharmaceutical culprit, as they can delay orgasm or eliminate it entirely.
Sexual pain disorders affect women almost exclusively and are known as dyspareunia (painful intercourse) or vaginismus (an involuntary spasm of the muscles of the vaginal wall that interferes with intercourse).
Dyspareunia may be caused by insufficient lubrication (vaginal dryness) in women. Poor lubrication may result from insufficient excitement and stimulation, or from hormonal changes caused by menopause, pregnancy, or breast-feeding. Irritation from contraceptive creams and foams can also cause dryness, as can fear and anxiety about sex.
It is unclear exactly what causes vaginismus, but it is thought that past sexual trauma (such as rape or abuse) may play a role. Another female sexual pain disorder is called vulvodynia or vulvar vestibulitis. In this condition, women experience burning pain during sex which seems to be related to problems with the skin in the vulvar and vaginal areas. The cause is unknown.
Erectile dysfunction from vascular disease is usually seen only amongst elderly individuals who have atherosclerosis. Vascular disease is common in individuals whom have diabetes, peripheral vascular disease, hypertension and those who smoke. Any time blood flow to the penis is impaired, erectile dysfunction is the end result. Hormones deficiency is a relatively rare cause of erectile dysfunction. In individuals with testicular failure like klinefelter's syndrome, or those who have had radiation therapy, chemotherapy or childhood exposure to mumps virus, the testes may fail and not produce testosterone. Other hormonal causes of erectile failure include brain tumors, hyperthyroidism, hypothyroidism or disorders of the adrenal gland. 
Structural abnormalities of the penis like Peyronie's disease can make sexual intercourse difficult. The disease is characterized by thick fibrous bands in the penis which leads to a deformed-looking penis. 
Drugs are also a cause of erectile dysfunction. Individuals who take drugs to lower blood pressure, uses antipsychotics, antidepressants, sedatives, narcotics, antacids or alcohol can have problems with sexual function and loss of libido. 
Priapism is a painful erection that occurs for several hours and occurs in the absence of sexual stimulation. This condition develops when blood gets trapped in the penis and is unable to drain out. If the condition is not promptly treated, it can lead to severe scarring and permanent loss of erectile function. The disorder occurs in young men and children. Individuals with sickle-cell disease and those who abuse certain medications can often develop this disorder. 
There are many factors which may result in a person experiencing a sexual dysfunction. These may result from emotional or physical causes.
Sexual dysfunction may arise from emotional factors, including interpersonal or psychological problems. Interpersonal problems may arise from marital or relationship problems, or from a lack of trust and open communication between partners, and psychological problems may be the result of depression, sexual fears or guilt, past sexual trauma, sexual disorders, among others.
Sexual dysfunction is especially common among people who have anxiety disorders. Ordinary anxiousness can obviously cause erectile dysfunction in men without psychiatric problems, but clinically diagnosable disorders such as panic disorder commonly cause avoidance of intercourse and premature ejaculation. Pain during intercourse is often a comorbidity of anxiety disorders among women.
Sexual activity may also be impacted by physical factors. These would include use of drugs, such as alcohol, nicotine, narcotics, stimulants, antihypertensives, antihistamines, and some psychotherapeutic drugs. For women, almost any physiological change that affects the reproductive system—premenstrual syndrome, pregnancy, postpartum, menopause—can have an adverse effect on libido. Injuries to the back may also impact sexual activity, as would problems with an enlarged prostate gland, problems with blood supply, nerve damage (as in spinal cord injuries). Disease, such as diabetic neuropathy, multiple sclerosis, tumors, and, rarely, tertiary syphilis may also impact on the activity, as would failure of various organ systems (such as the heart and lungs), endocrine disorders (thyroid, pituitary, or adrenal gland problems), hormonal deficiencies (low testosterone, estrogen, or androgens), and some birth defects.
The fourth edition of the Diagnostic and Statistical Manual of Mental Disorders lists the following psychological sexual disorders:
Since in many men the cause of sexual dysfunction is related to anxiety about performance, psychotherapy can help. Situational anxiety arises from an earlier bad incident or lack of experience. This anxiety often leads to development of fear towards sexual activity and avoidance. In return evading leads to a cycle of increased anxiety and desensitization of the penis.  In some cases, erectile dysfunction may be due to marital disharmony. Marriage counseling sessions are recommended in this situation.
Lifestyle changes such as discontinuing smoking, drug or alcohol abuse can also help in some types of erectile dysfunction.  Several medications like Viagra, cialis and Levitra have become available to help people with erectile dysfunction. These medications do work in about 60% of men. In the rest, the medications may not work because of wrong diagnosis or chronic history.
Although there are no approved pharmaceuticals for addressing female sexual disorders, several are under investigation for their effectiveness. A vacuum device is the only approved medical device for arousal and orgasm disorders. It is designed to increase blood flow to the clitoris and external genitalia. Women experiencing pain with intercourse are often prescribed pain relievers or desensitizing agents. Others are prescribed lubricants and/or hormone therapy. Many patients with female sexual dysfunction are often also referred to a counselor or therapist for psychosocial counseling.
A manual physical therapy, the Wurn Technique, which is designed to reduce pelvic and vaginal adhesion, may also be beneficial for women experiencing sexual pain and dysfunction. In a controlled study, Increasing orgasm and decreasing intercourse pain by a manual physical therapy technique, twenty-three (23) women reporting painful intercourse and/or sexual dysfunction received a 20-hour program of manipulative physical therapy. The results were compared using the validated Female Sexual Function Index, with post-test vs. pretest scores. Results of therapy showed improvements in all six recognized domains of sexual dysfunction. The results were significant (P </= .003) on all measures, with individual measures and P-values as follows: desire (P < .001), arousal (P = .0033), lubrication (P < .001), orgasm (P < .001), satisfaction (P < .001), and pain (P < .001). A second study to improve sexual function in patients with endometriosis showed similar statistical results.
The earliest attempts at treating sexual dysfunctions, especially erectile dysfunction, date back to Muslim physicians and pharmacists in the medieval Islamic world. They were the first to prescribe medication for the treatment of this problem, and they developed several methods of therapy for this issue, including a single-drug therapy method where a drug was prescribed and a "combination method of either a drug or food." Most of these drugs were oral medication, though a few patients were also treated through topical and transurethral means. Sexual dysfunctions were being treated with clinically tested drugs in the Islamic world since the 9th century until the 16th century by a number of Muslim physicians and pharmacists, including Muhammad ibn Zakarīya Rāzi, Thabit bin Qurra, Ibn Al-Jazzar, Avicenna (The Canon of Medicine), Averroes, Ibn al-Baitar, and Ibn al-Nafis (The Comprehensive Book on Medicine).
In modern times, the genuine clinical study of sexual problems is usually dated back no further than 1970 when Masters and Johnson's Human Sexual Inadequacy was published. It was the result of over a decade of work at the Reproductive Biology Research Foundation in St. Louis, involving 790 cases. The work grew from Masters and Johnson's earlier Human Sexual Response (1966).
Prior to Masters and Johnson the clinical approach to sexual problems was largely derived from the thinking of Freud. It was held with psychopathology and approached with a certain pessimism regarding the chance of help or improvement. Sexual problems were merely symptoms of a deeper malaise and the diagnostic approach was from the psychopathological. There was little distinction between difficulties in function and variations nor between perversion and problems. Despite work by psychotherapists such as Balint sexual difficulties were crudely split into frigidity or impotence, terms which too soon acquired negative connotations in popular culture.
The achievement of Human Sexual Inadequacy was to move thinking from psychopathology to learning, only if a problem did not respond to educative treatment would psychopathological problems be considered. Also treatment was directed at couples, whereas before partners would be seen individually. Masters and Johnson saw that sex was a joint act. They believed that sexual communication was the key issue to sexual problems not the specifics of an individual problem. They also proposed co-therapy, a matching pair of therapists to the clients, arguing that a lone male therapist could not fully comprehend female difficulties.
The basic Masters and Johnson treatment program was an intensive two week program to develop efficient sexual communication. Couple-based and therapist led the program began with discussion and then sensate focus between the couple to develop shared experiences. From the experiences specific difficulties could be determined and approached with a specific therapy. In a limited number of male only cases (41) Masters and Johnson had developed the use of a female surrogate, an approach they soon abandoned over the ethical, legal and other problems it raised.
In defining the range of sexual problems Masters and Johnson defined a boundary between dysfunction and deviations. Dysfunctions were transitory and experienced by the majority of people, dysfunctions bounded male primary or secondary impotence, premature ejaculation, ejaculatory incompetence; female primary orgasmic dysfunction and situational orgasmic dysfunction; pain during intercourse (dyspareunia) and vaginismus. According to Masters and Johnson sexual arousal and climax are a normal physiological process of every functionally intact adult, but despite being autonomic it can be inhibited. Masters and Johnson treatment program for dysfunction was 81.1% successful.
Despite the work of Masters and Johnson the field in the US was quickly over-run by ethusiastic rather than systematic approaches, blurring the space between 'enrichment' and therapy. Although it has been argued that the impact of the work was such that it would be impossible to repeat such a clean experiment.