BMC Public Health 2006, 6:127 http://www.biomedcentral.com/1471-2458/6/127 Background Lesbian, gay and bisexual (LGB) people experience preju- dice and discrimination [1] and may have higher rates of anxiety, depression, substance use disorders and suicidal behaviour than heterosexuals [2-5]. Furthermore, despite considerable data on the sexual behaviour of gay men, lit- tle is known about the prevalence of sexual dysfunction [6,7] and even less is known about sexual behaviour or dysfunction in lesbians [8] or bisexual people. Most research into the mental health of LGB people has been conducted in North America and many studies have included no comparison groups [7,9-11], recruited non- random samples [6,12] or applied unusual definitions of same sex attraction [4]. Few have distinguished gay and lesbian from bisexual people, classifying instead on any degree of same sex attraction [13], usually because of small samples. No previous study has assessed morbidity of gay, lesbian or bisexual people attending their family practitioners. Although 5% of the British population is gay or lesbian [14] random sampling often achieves insufficient num- bers [15] and/or such low percentages of LGB people that the research process becomes cumbersome and expensive [8]. We recruited people attending family practitioners in order to assess the importance of the sexual orientation of general practices attendees in London to their mental, physical and sexual function. Methods Participants and setting Two London (the Camden and Islington and the Enfield and Haringey) local research ethical committees approved the study. We recruited people attending their primary care physicians. 95% of the people in the UK are registered at general practices that serve as the first point of contact with health services. We approached a group of research general practices in a defined area of north London. None of the practices approached served only a LGB population nor did they advertise or offer special health care to LGB people. We asked consecutive people aged 18 to 75 attending these general practices to participate in the study and in each practice recruited attendees over a 4–8 week period. Each person approached to participate in the study was given a detailed information sheet on the study procedures. Those consenting to take part were asked to complete a questionnaire in a private setting in the gen- eral practice as they waited to see the doctor [16]. Materials The questionnaire contained: 1. Standard demographic questions: on age, sex, ethnicity, civil status and current occupation. 2. A question on participants' sexual orientation using Kinsey ratings based on sexual experiences [17]. The respondent was asked to circle any number from 1 to 7 that corresponded to the statement that best described their sexual experiences. These were as follows: 1 entirely heterosexual; 2 largely heterosexual, but with some homosexual experience; 3 largely heterosexual, but con- siderable homosexual experience; 4 equally heterosexual and homosexual; 5 largely homosexual, but with consid- erable heterosexual experience; 6 largely homosexual, but with some heterosexual experience and 7 entirely homo- sexual. 3. Short Form 12 (SF-12): This is a well-validated quality of life questionnaire. We used the 12-item version of this questionnaire that produces separate physical and psy- chological well-being scores [18]. 4. The General Health Questionnaire (GHQ): a measure of current mental health problems. Since its development, it has been extensively used in different settings and cul- tures [19-23]. The questionnaire was originally developed as a 60-item instrument but the GHQ-12, a shortened ver- sion of the questionnaire, has since been developed. The GHQ-12 is easy to complete and was designed to screen for psychological symptoms in the community. It is not a diagnostic instrument. There is evidence that the GHQ-12 is a consistent and reliable instrument when used in gen- eral population samples [24]. The GHQ asks whether the respondent has experienced a particular psychological symptom or behaviour recently. Each item is rated on a four-point scale (less than usual, no more than usual, rather more than usual, or much more than usual). 5. The four-item CAGE questionnaire [25], which is a known screening instrument for possible alcohol misuse. We also included one question on current consumption of cigarettes. 6. Questions about numbers of sexual partners in the pre- ceding four weeks in order to assess risk of sexually trans- mitted infection. 7. Four screening questions about sexual experiences under the age of 16 years [26]. These concerned a) some- one trying to or succeeding in having sexual intercourse with them b) touching, grabbing, kissing or rubbing up against them in public or private c) taking photographs of them naked or exhibiting parts of their body to them or performing a sex act in their presence and d) perpetrating oral sex or anal intercourse on them. 8. The brief sexual function questionnaire for men [27,28] and a modified version for women [29]. This question- naire collected information on sexual activity (i.e. mastur- Page 2 of 12 (page number not for citation purposes)