Definitions and Outcomes
Sexual dysfunction is highly prevalent in men and women, although estimates vary depending upon the definitions and means of assessment used. From a psychiatric perspective, most definitions are based upon the four-phase model of Masters and Johnson [1], and Kaplan [2].

The first phase, sexual desire, consists of the motivational or appetitive aspects of sexual response. Sexual urges, fantasies, and wishes are included in this phase. The second phase, sexual excitement, refers to a subjective feeling of sexual pleasure and accompanying physiologic changes. This phase includes penile erection in men and vaginal lubrication in women.

The third phase, orgasm or climax, is defined as the peak of sexual pleasure, with rhythmic contractions of the genital musculature in both men and women, and ejaculation in men. The final phase is resolution, during which a general sense of relaxation and well-being is experienced.

In men, a refractory period for erection and ejaculation usually occurs during this phase. Sexual dysfunctions can be considered an alteration in one or more phases of the sexual response cycle, and this four-stage model forms the basis for classification of the sexual dysfunctions in the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) [3].

Based upon this model, four major categories of sexual dysfunction are identified by DSM-IV as follows (Table 1): 1) sexual desire disorders, including hypoactive sexual desire disorder (HSDD) and sexual aversion disorder; 2) sexual arousal disorders, including female sexual arousal disorder (FSAD)  and male erectile disorder, or erectile dysfunction (ED); 3) orgasmic disorders, including female orgasmic disorder, male orgasmic disorder, and premature ejaculation (PE); and 4) sexual pain disorders, including dyspareunia and vaginismus. Additional categories include sexual dysfunction due to a general medical condition, substance-induced sexual dysfunction, and sexual dysfunction not otherwise specified. Examples of the latter category include a lack of subjective erotic feelings, despite presence of normal arousal and orgasm, or the presence of a sexual dysfunction of undetermined origin. A revised and expanded classification for female sexual dysfunction recently has been proposed [4••], which incorporates dysfunctions due to organic and psychogenic etiologies. The definitions of desire and arousal difficulties in women have been broadened, and a new category of nongenital sexual pain disorders has been proposed.

Sexual dysfunctions impact significantly on mood, selfesteem, interpersonal functioning, and overall life satisfaction [5,6]. In the Massachusetts Male Aging Study (MMAS) [7], a large-scale epidemiologic study of ED in middle-aged and older males, a strong correlation was observed between the occurrence of erectile difficulties and selfratings of depression. Men with partial or complete ED rated themselves as significantly more depressed than those with normal erectile function. Moreover, the association between depression and ED was found to be independent of age, health status, or other mediating factors.

Similarly, in the National Health and Social Life Survey (NHSLS), a population-based survey of sexual behavior in men and women aged 18 to 59 [5], arousal and desire difficulties in both men and women were strongly associated with decreased physical and emotional satisfaction with the partner relationship.
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Sexual dysfunctions are highly prevalent, affecting about 43% of women and 31% of men. Hypoactive sexual desire disorder has been reported in approximately 30% of women and 15% of men in population-based studies, and is associated with a wide variety of medical and psychologic causes. Sexual arousal disorders, including erectile dysfunction in men and female sexual arousal disorder in women, are found in 10% to 20% of men and women, and is strongly age-related in men. Orgasmic disorder is relatively common in women, affecting about 10% to 15% in community-based studies. In contrast, premature ejaculation is the most common sexual complaint of men, with a reporting rate of approximately 30% in most studies. Finally, sexual pain disorders have been reported in 10% to 15% of women and less than 5% of men. In addition to their widespread prevalence, sexual dysfunctions have been found to impact significantly on interpersonal functioning and overall quality of life in both men and women.

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Raymond C. Rosen, PhD

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