Adequate sexual expression is essential to many human relationships and provides a sense of physical, psychological and social well-being. Epidemiological and clinical studies show that depression and schizophrenia are associated with impairment of sexual function and satisfaction, even in untreated patients. Most antidepressant and antipsychotic drugs have adverse sexual effects but it is difficult accurately to identify the incidence of treatment-emergent dysfunction, as disturbances can be reliably detected only from systematic enquiries made at baseline and during treatment. Growing awareness of the adverse effects of psychotropic drugs has led to attempts to use adjuvants or substitute treatments to resolve sexual dysfunction. More studies of the effects of antidepressant and antipsychotic drugs on sexual function are needed.
The normal sexual response is conventionally divided into the four phases listed below, and disorders can occur at one or more of these phases.
- Desire: typically this consists of fantasies about, and the desire to have, sexual activity.
- Excitement: a subjective sense of sexual pleasure and accompanying physiological changes, namely penile tumescence and erection in men and pelvic vasocongestion, swelling of the external genitalia, vaginal lubrication and expansion in women.
- Orgasm: this is when sexual pleasure peaks, with release of sexual tension and rhythmic contraction of the perineal muscles and reproductive organs. In men, the sensation of ejaculatory inevitability is followed by ejaculation of semen. In women, contractions of the outer third of the vaginal wall occur.
- Resolution: a sense of muscular relaxation and general well-being. Men are physiologically refractory to erection and orgasm for a variable period after orgasm, whereas women may respond to further stimulation.
The ICD–10 (World Health Organization, 1992) uses the term ‘sexual dysfunction’ to cover the ways in which an individual is unable to participate in a sexual relationship as he or she would wish. This classification has 10 subdivisions (F52.0–F52.9), each describing different forms of dysfunction. The DSM–IV (American Psychiatric Association, 1994) uses a similar scheme. Whenever possible, doctors should specify which form of sexual dysfunction is present, as these have differing causes and require different treatment approaches.
Some types of dysfunction occur in both men and women, although women tend to present with complaints about the subjective quality of sexual experience (e.g. lack of desire), whereas men often describe the failure of a specific response (such as erection) but a continuing sexual desire.
Epidemiology of sexual dysfunction
This area has not been studied extensively. Nathan (1986) evaluated 22 studies of sexual behaviour in the general population but concluded that methodological problems in the surveys meant that only broad estimates could be made. The prevalence of inhibited sexual desire was 16% for men, 35% for women; for erectile dysfunction and premature ejaculation the prevalence values were 10–20% and 35% of men, respectively; female orgasmic difficulties had a prevalence of 5–15%.
A US study found that sexual dysfunction in the general population is more prevalent in women (43%) than men (31%) (Laumann et al, 1999). Using latent class analysis, symptoms during the previous 12 months could be grouped into three categories. In women, these were low sexual desire (22% prevalence), arousal or excitement problems (14%) and sexual pain (7%); in men, they were premature ejaculation (21%), erectile dysfunction (5%) and low sexual desire (5%).
Reported rates of sexual dysfunction vary considerably, reflecting differences in the study population and types of dysfunction being assessed. Other studies with data for both genders show a higher prevalence of sexual dysfunction in women than in men (Ernst et al, 1993; Dunn et al, 1998) and confirm the results for the most common sexual dysfunction in both men and women.
Many factors influence the reported incidence of sexual dysfunction. The first is the method of enquiry. In a prospective study of out-patients with depression, for example, the incidence of sexual dysfunction was 14% when relying on spontaneous reporting. However, this rose to 58% when patients were questioned directly by doctors (Montejo-González et al, 1997). The second factor is that the expectation people have of their sexual performance and their willingness to discuss problems vary between cultures (Bhugra & De Silva, 1993). In the third place, many terms used to define sexual dysfunction are subjective and partly dependent on ideas of what is ‘normal’. Finally, temporal trends can occur as increased awareness of sexual matters and availability of treatment increase the number of those who perceive themselves to be suffering from sexual dysfunction.
Sexual dysfunction in depression
Depression is characterised by loss of interest, reduction in energy, lowered self-esteem and inability to experience pleasure: irritability and social withdrawal may impair the ability to form and maintain intimate relationships. It would be surprising if this constellation of symptoms did not produce difficulties in sexual relationships (Baldwin et al, 1997).
In an early study of 132 patients with depressive disorders, loss of sexual interest (characterised by loss of libido or decrease of sexual desire or potency) was reported by 72% of patients with unipolar disorder and 77% of those with bipolar disorder (Casper et al, 1985). Loss of sexual desire may be the presenting complaint in some patients who are found to have significant depressive symptoms only after direct questioning. In others, low sexual desire may pre-date other features of depression (Schreiner-Engel & Schiavi, 1986).
Comparative studies indicate higher levels of sexual dysfunction in patients with depression than in controls (Table 1⇓). Although the incidence of specific types of sexual dysfunction varies across studies, loss of sexual desire may be more common than disorders of arousal and orgasm. For example, in one comparative study, changes in libido were significantly more common in patients with depression, but the prevalence of impotence, orgasmic or ejaculatory problems did not differ from controls (Mathew & Weinman, 1982). The prospective Zurich cohort study (Ernst et al, 1993) showed that the overall prevalence of sexual problems in subjects with depression (including major depression, dysthymia and recurrent brief depression) was about twice that in controls (50% v. 24%). This difference encompassed emotional problems, sexual dysfunction and both decreased and increased libido. The study findings were from a group of young people (28–35 years old) and are not necessarily applicable to older age groups (Angst, 1998).