Sexual Disorders and Sexual Dysfunction

Overview

Sexual disorders are extremely common. It has been estimated that 43% of women and 31% of men in the US suffer from sexual dysfunction. Lack of sexual satisfaction is associated with significant emotional distress (e.g., depression, marital conflict) and physical problems (e.g., cardiovascular disease, diabetes mellitus). Individuals with sexual problems are often reluctant to seek assistance from a physician and may first experiment with any number of self-help methods. However, with the introduction of PDE-5 inhibitors, such as sildenafil (Viagra) for the treatment of erectile dysfunction and the increased interest in pharmacological therapy for female sexual disorders, the frequency of complaints related to sexual dysfunction in primary care practice has risen to nearly 15% to 20% of visits. Nevertheless, the incidence of sexual problems is related to the frequency with which providers take a sexual history.

The new Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), has made several important changes to the classification of sexual disorders. Previously grouped into one chapter, sexual disorders are now separated into three chapters: sexual dysfunctions, paraphilic disorders, and gender dysphoria.

Sexual dysfunction is characterized by a clinically significant disturbance in the ability to respond sexually or to experience sexual pleasure. Previously, it was defined according to the physiological sexual response cycle, a model increasingly felt too simplistic. Criteria are now more precise, requiring 6 months of symptoms and a severity rating. Some disorders are now gender-specific (e.g., male hypoactive sexual desire disorder), and others have been merged (e.g., genito-pelvic pain/penetration disorder instead of vaginismus and dyspareunia), or deleted (e.g., sexual aversion disorder). The sexual dysfunctions are further classified as lifelong or acquired and situational or generalized. The DSM-5 introduces “associated features,” such as relationship and medical factors, which support particular diagnoses.

The DSM-5 for the first time distinguishes between paraphilias and paraphilic disorders. Paraphilias are defined as persistent and intense atypical sexual interests and considered normal. Paraphilic disorders are paraphilias that cause distress or impairment to the individual or that result in personal harm or risk of harm to others.

Finally, gender dysphoria replaces gender identity disorder and describes dissatisfaction with one's natal sex. The concepts are similar; however, gender dysphoria abandons the use of “cross-gender,” allowing for an “alternative” (undefined) gender. All sexual disorders must cause clinically significant distress or an impairment of social function before a diagnosis can be made.

Epidemiology and Risk Factors

Sexual disorders affect individuals across the epidemiological spectrum. They occur more often in women than in men and are more frequent with advanced age, lower socioeconomic status, obesity, sedentary lifestyle, co-existing medical (e.g., cardiovascular) and psychiatric conditions, and history of sexual trauma. The prototypical paraphilic is young, white, and male and more likely to suffer from ADHD, substance abuse, major depression or dysthymia, and/or a phobic disorder.

Pathophysiology

Sexual function depends on complex interactions among the brain, hormones, and the vascular system. Neural modulators of sexual desire, arousal, and orgasm include dopamine, melanocortin, estrogen, and testosterone. At the vascular level, nitric oxide (NO) plays a critical role in regulating vaginal smooth muscle tone and intrapenile blood flow. In fact, PDE-5 inhibitors act by prolonging the effects of NO.

The sexual response cycle concept is useful in understanding sexual problems. The stages vary with age and physical status and are affected by medications, diseases, injuries, and psychological conditions ( Table 36-1 ). Three major models have been proposed.

Masters and Johnson developed the first model of the human sexual response, consisting of a linear progression through four distinct phases: (1) excitement (arousal); (2) plateau (maximal arousal before orgasm); (3) orgasm (rhythmic muscular contractions); and (4) resolution (return to baseline). Following resolution, a refractory period exists in men.

Kaplan modified the Masters and Johnson model by introducing a desire stage (neuropsychological input). The Kaplan model consists of three stages: (1) desire; (2) excitement/arousal; and (3) orgasm (muscular contraction).

Most recently, Basson, recognizing the complexity of the female sexual response, proposed a biopsychosocial model of female sexuality that consists of four overlapping components: (1) biology; (2) psychology; (3) sociocultural factors; and (4) interpersonal relationships. The model acknowledges that many factors may stimulate a woman's receptivity for sex. Indeed, sexual satisfaction may be prompted by such factors as emotional closeness and may still be achieved without direct desire. Additionally, it is known that physical measurements of female arousal (such as increased vaginal secretions) are poorly correlated with sexual satisfaction.

Aging is associated with changes in the normal human sexual response. Men are slower to achieve erections and require more direct genital stimulation. Women have decreased levels of estrogen, leading to decreased vaginal lubrication and narrowing of the vagina. Testosterone levels in both sexes decline with age, which may result in decreased libido.

Clinical Features and Diagnosis

The diagnosis of a sexual problem relies on a thorough medical and sexual history, supplemented by physical examination and laboratory testing. A mixed organic/psychological basis is often present. Physical disorders, surgical conditions ( Table 36-2 ), medications, and use or abuse of drugs ( Table 36-3 ) can affect sexual function directly or cause secondary psychological reactions that lead to a sexual problem. Psychological factors may predispose to, precipitate, or maintain a sexual disorder ( Box 36-1 ).