Drug-Induced Sexual Dysfunction
Substance-induced sexual dysfunction, for example, can involve loss of interest in sex, inability for the male to become erect, impaired orgasm, and pain during intercourse. Various medications also can produce symptoms of sexual dysfunction.

There are a number of medical conditions that can cause sexual dysfunction, including various neurological problems (e.g., multiple sclerosis), endocrine conditions (e.g., diabetes mellitus), vascular conditions, and several different infections. These are termed biogenic conditions.

In his book "Human Sexual Response", Lief described five sexual response phases: desire, arousal, vasocongestion, orgasm, and satisfaction. Sexual dysfunction can occur in any of these areas.

If the dysfunction is a chronic problem, such as a woman who has always experienced pain during intercourse, it is called primary dysfunction. If the dysfunction is situational, such as a man who previously had no difficulty achieving erection but begins to experience this problem at the beginning of a new relationship, it is called secondary dysfunction.

Primary or secondary dysfunction can occur in any of the five domains of sexual response. Dysfunctions associated with sexual desire include hypoactive sexual desire disorder and sexual aversion disorder.

Absence of Sexual Desire
In the first of these, the individual has a persistent absence of sexual fantasies or desire for participation in sexual activity. In the second disorder, there is a complete or near complete aversion to contact with a partner's genitals. These conditions often reflect serious emotional problems, although individuals may be responsive to intensive psychotherapy combined with sexual therapy.

Sexual arousal disorders are found in both males and females. Males may be interested in sex but suffer from impotence or erectile dysfunction, while females are unable to maintain the lubrication-vaginal swelling response of normal sexual excitement.

In their book, "Human Sexual Inadequacy", Masters and Johnson asserted that 90% of impotency cases were psychogenic in origin. Even in older men, they maintained, emotional issues rather than medical problems are the main causes of impotence. Masters and Johnson reported great success in treating impotence with short-term therapy, especially when it had its roots in fear of failure and performance anxiety.