Sexual dysfunction: overview of prevalence, etiological factors, and treatments.

Sexual dysfunction can impact a person's ability to form or sustain intimate relationships and has been found to interact with mental health conditions such as anxiety and depression. Yet epidemiological, etiological, and health associations to sexual dysfunctions have only begun to be explored. The result of the research to date indicates that neurovascular mechanisms may be important for both sexes, and new classes of drugs are being explored with significant treatment potential (Bancroft, 1998; Everaerd & Laan, 2000; Heaton, 1998; Rowland & Burnett, 2000).

PREVALENCE ESTIMATES

Recent research indicates that sexual problems are highly prevalent in both sexes. Community samples estimates range from 10% to 52% of men and 25% to 63% of women (Feldman, Goldstein, Hatzichristou, Krane, & McKinlay, 1994; Frank, Anderson, & Rubenstein, 1978; Rosen, Taylor, Leiblum, & Bachman, 1993; Spector & Carey, 1990). The National Health and Social Life Survey (NHSLS), a 1992 national probability sample of 1410 men and 1749 women between the ages of 18 and 59 years living in U.S. households, comprises our best estimate of sexual problems in the U.S. (Laumann, Gagnon, Michael, & Michaels, 1994; Laumann, Paik, & Rosen, 1999). In the analyses that included only those individuals who reported any sexual activity with a partner in the prior 12-month period, the prevalence of sexual dysfunction was 43% for women and 31% for men (Laumann, et al., 1999). Although this study did not use the Diagnostic and Statistical Manual (DSM-IV, American Psychiatric Association, 1994) criteria, and thus does not connote clinical dysfunction, it provides an estimate of potential sexual dysfunction, and we will often rely on these figures as the dysfunctions are discussed. Nevertheless, we must keep in mind that these are not formal clinical diagnostic categories which in fact may overestimate the prevalence (e.g., Simons & Carey, 2001), even though the Laumann et al. (1999) figures may themselves be conservative because they exclude the 139 men and 238 women who were sexually inactive in the past year.

ETIOLOGICAL FACTORS

Though few data exist, there are some general etiological indicators that have been implicated in specific sexual dysfunctions. For example, the Massachusetts Male Aging Study (MMAS) reported erectile dysfunction in 34.8% of men aged 40 to 70 years old with age, health status (cardiovascular disease, diabetes, disease-related medications, cigarette smoking), and emotional factors (depression, anger) being highly related to the erectile disorder (Feldman et al., 1994). In the NHSLS, a variety of risk factors were identified using adjusted odds ratios (Laumann et al., 1999). Demographic factors that influence reported problems included age, education, and race/ethnicity. For women, sexual problems, except for trouble lubricating, tended to decrease with age; for men, erection problems in particular increased with age. Higher education was correlated with less dysfunction. Though race and ethnicity effects were more modest, Hispanics reported the least dysfunction, followed by the White and then the Black samples, which showed higher rates. Among the health and lifestyle variables, the NHSLS found that stress and emotional problems were related to experiencing sexual problems. Health problems were more significant for men's dysfunctions and sexual pain disorders in women than for women's sexual desire and arousal problems. Reported urinary tract infections were associated with sexual arousal and pain disorders in women and erectile dysfunction in men. Among the social status variables, all categories of female sexual dysfunction were associated with decreasing household income while only erectile dysfunction was associated in men. Liberal sexual attitudes were associated only with premature ejaculation in men. Several sexual experience variables were important. Men reporting any same-sex sexual activity were more likely to experience premature ejaculation and low sexual desire than men who reported no same sex experience, though this variable did not differentiate for women. Arousal disorder in women was highly associated with their experience of adult-child sexual contact or any experience of male sexual force. Women's desire disorder was also associated with male sexual force. For men, being sexually touched before puberty was associated with a three-fold increase in erectile dysfunction and a two-fold increase in premature ejaculation and low sexual desire compared to men without this history. Men who reported sexually forcing a woman were 3.5 times as likely to report erectile dysfunction. While the MMAS and the NHSLS data sets sample only a small percentage of potential etiological factors, they suggest that sexual dysfunctions are complexly determined and highly related to physical and psychosocial dimensions of an individual's life. This implies that preventative treatment measures would be useful, and that optimal treatments require careful histories and the ability to impact psychological and physiological sexual response.

EFFICACY AND SEXUAL DYSFUNCTION TREATMENT

In treating sexual problems with either pharmacological/medical or psychological techniques, one hopes for changes in physical (genital response, orgasms) and subjective (increased desire, ease of orgasm) responses. Psychological techniques use cognitive and/or behavioral methods to change sexual problems. Historically, this position was crystallized by Masters and Johnson (1970), whose work was as revolutionary in its time for impacting psychotherapy as sildenafil citrate (Viagra: Pfizer, Inc.) has been for pharmacological treatments. Medical treatments aim to change a person's physiological response. The focus of medical treatments for the past 20 years has been primarily on male erectile disorder, and only recently on premature ejaculation in men and sexual arousal and desire in women.

Before reviewing sexual dysfunction treatments, it is important to briefly note the differences between typical randomized clinical trials which test medications and those testing psychological interventions (see Heiman & Meston, 1997). These include: (a) Psychological placebos require a consideration of many variables and, under most conditions, are ethically questionable; (b) double-blind designs are not feasible in psychosexual therapy; (c) treatment delivery systems are more variable in psychosexual therapy than in medication provision; (d) adequate comparison groups are needed and currently there are few available for psychological treatments; and (e) endpoints are more restricted and unidimensional in pharmacology clinical trials than in psychosexual studies.

In 1995, the American Psychological Association (APA) Task F6rce on the Promotion and Dissemination of Psychological Procedures proposed two categories of empirically supported treatments (ESTs): well-established and probably efficacious (APA, 1995). Well-established treatments require group studies by different investigators by showing superiority to another treatment or placebo, or by demonstrating equivalency to an established treatment in studies with adequate statistical power; or a large series of well-designed single case studies compared to another treatment or placebo; using treatment manuals and clear specification of patient/client samples.

Probably efficacious criteria are somewhat less stringent: two studies showing treatment is more effective than a waiting-list control group, or studies otherwise meeting well-established criteria, or at least two good studies demonstrating effectiveness but flawed by client sample heterogeneity, or a small series of single case design studies otherwise meeting the well-established treatment criteria. Since the original report of the task force there has been further discussion of the criteria and meaning of empirically supported treatment (e.g., Berkovec & Castonguay, 1998; Chambless & Hollon, 1998). There is recognition that some level of efficacy must be demonstrated with controlled research with a delineated population. Efficacy research is similar in scope and intent to traditional randomized clinical trial (RCT) research.

After establishing efficacy there is reason to examine treatment effectiveness or utility, referring to whether treatment can be shown to be beneficial in actual clinical practice. Effectiveness addresses the concept of generalizability that a RCT is often unable to assess since sample selection is more criteria restricted than in clinical practice. To test efficacy, quasiexperimental and nonexperimental designs may be usefully employed.

A number of sexual dysfunctions have treatment data that meet the probably efficacious criteria for an empirically supported treatment. Few meet the well-established criteria. Reasons for this are summarized elsewhere (Heiman & Meston, 1997). The primary issues have been funding and availability of comparable treatments and ethical placebos.

EMPIRICALLY SUPPORTED TREATMENTS BY SEXUAL DYSFUNCTION CATEGORY

Sexual Desire Disorders

Although a Consensus Conference was convened in the late 1990s to propose revisions to the diagnostic system for female sexual dysfunction (Basson et al., 2000), we will here use the DSM-IV (APA, 1994) criteria since all of the research to date has had the DSM system available and it is the major diagnostic system used in U.S. research. The DSM-IV lists two categories of sexual desire disorders, Hypoactive Sexual Desire and Sexual Aversion. Hypoactive Sexual Desire (HSD) is defined as persistently or recurrently deficient (or absent) sexual fantasies and desire for sexual activity. This sexual category is of special concern to women since the Laumann et al. (1994) national probability-sampled U.S. data revealed that 33.4% of women and 15.8% of men reported a lack of sexual interest for several months or more during the past year. Sexual Aversion refers to persistent or recurrent extreme aversion to, and avoidance of, genital sexual contact with a sexual partner. There are no prevalence figures available for sexual aversion but it is thought to be a rather rare disorder.

Although many different approaches have been tried on a case-by-case basis (Leiblum & Rosen, 1988), there are almost no controlled studies documenting an efficacious approach for either disorder in men or women. Recently, a waiting-list controlled study testing a cognitive-behavioral treatment for HSD has been reported to show improvement in sexual and marital functioning in women with HSD (Trudel et al., 2001). There is also one uncontrolled prepost study of "impaired sexual desire," using a modified Masters and Johnson (1970) approach with 154 British couples presenting for treatment (Hawton & Catalan, 1986). Only two of the men reported impaired sexual interest so their data can not be discussed. However, of the 57% of the women reporting impaired desire, 56% were rated as having the problem largely or fully resolved after a mean of 14.8 treatment sessions. The treatment approaches cited would be promising treatments to compare to each other or to medications in an RCT treating HSD.

There currently are no effective pharmacological agents for HSD in men or women. There is evidence that testosterone can be an effective treatment for individuals who are hypogonadal, or who have other conditions causing low levels of bioavailable testosterone (Davis, 1998; Heaton, 1998), but careful research specifically treating low sexual desire is lacking. One study has shown some promise for women who have had a hysterectomy and oophorectomy and who used a transdermal testosterone patch compared to placebo in combination with oral conjugated equine estrogen (Shifren et al., 2000). At the higher testosterone dose (300[micro]g), the women reported increases in fantasy, masturbation, and sexual intercourse as well as greater well-being. However, the higher dose showed testosterone levels considerably above the normal premenopausal range, so longer-term effects of this dose will need to be studied further. The clinical and research data raise the obvious point that the hypoactive sexual desire category would be best subdivided into logical subcategories by age and hormonal status, as well as the DSM-IV modifiers of Lifelong/Acquired and Global/Situational (Heiman, 2001).

Sexual Arousal Disorders

Two categories of sexual arousal disorders are defined by DSM-IV: Female Sexual Arousal Disorder (FSAD) and Male Erectile Disorder (ED). In the DSM-IV, FSAD is described in terms of the inability to attain, or to maintain until completion of the sexual activity, an "adequate lubrication-swelling response of sexual excitement." A revision of this category by an international consensus panel proposed that this category include a lack of subjective excitement (Basson et al., 2000). There are no prevalence data for FSAD, and clinically it is rarely identified as separate from either sexual desire or orgasmic disorders. Of controlled studies specifically related to FSAD, none are published and few have been reported. Since the release of sildenafil citrate for men in 1998, there has been considerable interest in finding parallel agents for women. Sildenafil citrate, a phosdiesterase inhibitor type 5, has a relaxant effect on human cavernous tissues (at this point still best demonstrated in the male penis as only indirect data exist for the human female). Several different pharmaceutical agents are under investigation, including those with more peripheral action on genital vasocongestion such as sildenafil citrate and l-arginine, and those acting on the brain such as apomorhine sl, a dopaminergic chemical (Bartlik, Kaplan, Kaminetsky, Roentsch, & Goldberg, 1999; Everaerd & Laan, 2000). No differences in female sexual arousal were found when sildenafil was compared to a placebo in a double-blind study of over 500 women with FSAD in Canada, Europe, and the U.K. (Basson et al., 2000). In sexually functional premenopausal women in The Netherlands, sildenafil produced greater vaginal vasocongestion than did placebo to sexually explicit stimuli in a laboratory study. However, there was no difference in genital or subjective response when sildenafil was compared to placebo in postmenopausal women with FSAD (Laan, van Lunsen, Everaerd, Heiman, & Hackbert, 2000). The only study thus far to show significant changes in sexual functioning was a study of young (ages 22-28) Italian women with arousal disorders (Caruso, Intelisano, Lupo, & Agnello, 2001). All were ovulating normally and not on hormonal medications. Arousal, orgasm, and the frequency of enjoyment and vaginal intercourse improved significantly in the women treated with 25mg or 50mg of sildenafil. At this point it is unclear whether sildenafil might be effective for a specific subgroup among women with sexual dysfunction. Given the lack of genital focus of women, it is possible that genitally targeted pharmacological agents would be best compared to and combined with psychological treatments.

Male ED is a common clinical complaint, though only 10.4% of men between 18 and 59 years of age reported it being a problem in the past year (Laumann et al, 1994). ED prevalence increases with age (Feldman et al., 1994; Laumann et al., 1999). It is defined as the persistent or recurrent inability to attain or maintain an adequate erection until the completion of the sexual activity. The primary psychological treatments that have been used to treat ED are systematic desensitization and general sex therapy that includes a combination of education, sensate focus exercises, and sexual communication skills. Of the six (N = 146 men) comparison controlled studies, systematic desensitization was found to be better than psychoanalytic treatment and an attention placebo (Heiman & Meston, 1997). Among the wait-list and own controlled studies (N = 85), masturbation, sex education, behavioral assignments, and communication skills resulted in increased satisfaction with erectile functioning, sexual frequency, and increased marital satisfaction (Heiman & Meston, 1997).

Erectile dysfunction in men is unique among the sexual dysfunctions for the variety of medical treatments available (prostheses, injections or urethral suppositories of PGE-1, vacuum devices) but a completely different option for treatment began with the emergence of sildenafil (Goldstein, Lue, Padma-Nathan, Rosen, Steers, & Wicker, 1998). Sildenafil marked the beginning of an effective and relatively safe pharmacological agent for treating ED with a variety of etiologies, including psychogenic or non-illness, non-injury induced erectile disorder. In addition, this medication could be taken 1 hour prior to sexual activity as opposed to continuously. The appeal and success of sildenafil has stimulated interest in other medications for ED, including other phosphodiesterase inhibitors, and they are currently in various stages of research (Rowland & Burnett, 2000).

Orgasmic Disorders

These disorders include Female Orgasmic Disorder, Male Orgasmic Disorder, and Premature Ejaculation. Female Orgasmic Disorder is defined in the DSM-IV as persistent or recurrent delay in, or absence of, orgasm following a normal sexual excitement phase. Difficulty with orgasm is common, reported by 24.1% (Laumann et al., 1994). There are effective psychological treatments for this disorder, though treatments are more effective for primary (never experiencing orgasm) than secondary (infrequent or situational) orgasmic problems (Andersen, 1983; Heiman, 2000). Across all comparison controlled studies (N = 577), using 6 to 14 sessions, directed masturbation (DM) was more effective than systematic desensitization; and DM plus sensate focus was more effective than sensate focus alone (Heiman & Meston, 1997). Although group, individual, and couple therapies appear to be effective, comparisons between them are too infrequent to make any conclusions. For most criteria, primary orgasmic disorder fits the well-established efficacy designation, and secondary orgasmic disorder fits the probably efficacious criteria. The difficulty with these designations is that most of the studies have significant weaknesses in how well they characterize their samples.

Male Orgasmic Disorder is uncommon, with 8.3% of men reporting problems with lack of orgasm in the past year (Laumann et al., 1994) and it being rather rarely treated in clinics. There are no controlled treatment studies for this condition, though there are case examples and the original Masters and Johnson (1970) program data.

For both female and male orgasmic disorder, a new subcategory has emerged in the past decade, related to pharmacologically induced orgasmic disorder. This refers primarily to the selective serotonin reuptake inhibitor (SSRI) class of drugs, which have the known side effect of delayed or absent orgasm in men and women. Other psychotropic medications, including other antidepressants, have been found to affect sexual functioning but with more variable impacts and lower rates of being prescribed (Meston & Frohlich, 2000; Rosen, Lane, & Menza, 1999). Though exact frequencies are rarely documented, orgasmic disorder side effects seem to be reported in 9% to 40% of patients taking SSRIs, with females reporting symptoms more often than men (Rosen et al., 1999). There are no prospective comparative studies comparing hypothesized augmentation (to SSRI) agents (Rosen et al., 1999), though one recent report of women on fluoxetine suggests adding dopaminergic and serotonergic agents did not improve sexual side effect more than placebo (Michelson, Bancroft, Targum, Kim, & Tepner, 2000). It is unlikely that pharmacologically induced orgasmic disorder can be impacted by a psychological intervention alone.

Premature ejaculation is defined as the persistent or recurrent ejaculation with minimal sexual stimulation before, on, or shortly after penetration and before the person wishes it. It is the most common sexual problem reported in men, with approximately 28.5% of U.S. men reporting it to be a problem during the past year (Laumann, et al, 1994). The primary psychological intervention that has been used for premature ejaculation is the squeeze technique (Masters and Johnson, 1970). This technique involves stimulating the penis to full erection and almost to the point of ejaculation ("moment of inevitability") and then applying a firm squeeze just below the glans of the penis. Stimulation then resumes and two more trials occur before the person allows himself to ejaculate. It is usually first practiced in masturbation and then in partner sex. Although Masters and Johnson (1970) found excellent success (97% treatment success) treating 189 men with this condition, they had no comparison group. The only controlled (own-control) study testing this procedure found that foreplay duration significantly increased, as did intercourse duration (Heiman & LoPiccolo, 1983). Some of these gains decreased at 3-month follow-up post therapy (Heiman & Meston, 1997). The pause technique, a variant of the squeeze technique, is often used by clinicians (e.g., Kaplan, 1989) but there do not appear to be efficacy evaluations of this technique.

The SSRI side effect of orgasm delay has been incorporated into the pharmacological treatment of premature ejaculation. Clomipramine, sertraline, fluoxetine, and paroxetine have been tested in placebo-controlled or comparison treatment studies, and have been found to significantly increase latency to ejaculation (Althof, 1995: Althof et al., 1995; Rowland & Burnett, 2000) and sexual satisfaction (Althof, 1995). Thus pharmacological intervention can be a reliable source of improving ejaculation latency and possibly of sexual satisfaction for those men who wish to take medication for this condition (Rowland & Burnett, 2000). There is no evidence to date that the medications can be discontinued without the PE returning.

Genital Pain Disorders

The two categories of pain disorders are Dyspareunia and Vaginismus. Vaginismus without concurrent dyspareunia appears to be a relatively rare condition. Over their 5-year study, Masters and Johnson (1970) treated only 29 women with vaginismus compared to 342 women who were treated for orgasmic disorders. The low prevalence of this condition may play a role in the fact that there are no treatment comparison studies. There are two uncontrolled studies (total N = 54) plus a number of case studies. Almost all studies used a gradual dilation procedure with considerable success. Completed sexual intercourse was possible in approximately 75% to 100% of women by the end of treatment. In the past 10 years, perineal biofeedback procedures have been used for both diagnosis and treatment of vaginismus, though no empirical data are available for this diagnosis (Glazer, Rodke, Swencionis, Hertz, & Young, 1995). There is considerable evidence that this is a promising and useful procedure either by itself or with dilators, and sex therapy, but to date no comparison studies have been published.

Dyspareunia generally refers to pain associated with intercourse, but the location, duration, and patterns of pain can be quite variable. Dyspareunia is defined as pain during sexual intercourse. The NSHLS survey asked about "pain during sexual activity" and found that 3% of men and 14.4% of women reported this as a problem during the past 12 months (Laumann et al., 1994). Vulvar vestibulitis syndrome (VVS) is thought to be the most common subcategory of dyspareunia and it has a more precise diagnosis (Bergeron, Binik, Khalife, & Pagidas, 1997; Geotsch, 1991). There are very limited reports of treatment success with the general category of dyspareunia and no controlled studies. However, there are some suggestions from research with VVS patients that a psychologic treatment may be helpful (Bergeron, 1999; Bergeron et al., 1997; Glazer et al., 1995). Bergeron reported on a randomized comparison study and found that vestibulectomy resulted in significantly higher rates of improvement than biofeedback or a pain management]sex therapy intervention. However, mean levels of self-reported pain during interecourse were signifcantly lower at posttreatment for all three treatment conditions, and vestibulectomy patients were not significantly different from biofeedback patients on this measure. Perineal biofeedback may be particularly effective when there is presumed hypertonicity of the pelvic floor muscles. Preliminary work by Glazer et al. (1995) found that after 28 weeks of biofeedback training practice, 17 out of 33 women with VVS reported pain-free intercourse.

In spite of indications of effective treatment for a notable number of women with genital pain disorders, the lack of controlled studies prevents us from concluding that there are any clearly efficacious treatments for women. Given the more recent research, we can expect that new treatments will evolve that will be combination therapies of more than one intervention for the majority of cases (Bergeron, 1999).

CONCLUSIONS AND RECOMMENDATIONS

(1.) Sexual dysfunctions are very prevalent in the United States, with individual disorder estimates ranging from 8% to 33%.

(2.) Sexual dysfunctions are correlated with other health conditions, particularly those dealing with the cardiovascular system, common diseases (diabetes, high blood pressure, heart disease), health habits (cigarette smoking and possibly high alcohol consumption), and mental health (anxiety, depression).

(3.) Adequate sexual functioning appears to be associated with personal well-being and ongoing relationship stability, though this may be more true for men than women.

(4.) Research is lacking in understanding sexual functioning, sexual disorders, and the impact of treatments on specific symptoms and broader health issues for individuals and couples.

(5.) Particular areas of treatment research that are important are (a) prevention of sexual disorders using a current knowledge from different disciplines and (b) treatments that compare and combine psychological and pharmacological approaches to dysfunctions. As has been shown in the research on depression and anxiety (e.g., Keller et al., 2000), different treatment choices are important for patient consumers and combined treatments often are more efficient and enduring.

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Julia R. Heiman
University of Washington School of Medicine

Address correspondence to Julia R. Heiman, Ph.D., University of Washington Outpatient Psychiatry Center, 4225 Roosevelt Way NE, Suite 306, Seattle, WA 98105; e-mail: [e-mail].