Sexual health is a state of physical, emotional, mental and social well-being relating to sexuality. It's not merely the absence of disease, dysfunction or infirmity.
Sexual health is about having a positive and respectful approach to sexuality and sexual relationships. It's also about the possibility of having pleasurable and safe sexual experiences, free of coercion, discrimination and violence.
To get and maintain sexual health, a person's sexual rights must be respected, protected and fulfilled.
Human rights means each person must respect the rights of each other person, including respect for cultural and societal norms.
Sexual rights embrace human rights already recognised in national laws, international human rights documents and other consensus statements.
The sexual rights concept means a person has the right, free of coercion, discrimination and violence, to:
- the highest attainable standard of sexual health, including access to sexual and reproductive health care services
- seek, get and give out information related to sexuality
- sexuality education
- gain respect for their body
- choose their partner
- decide to be sexually active or not
- enter into consensual sexual relations
- enter into consensual marriage
- decide whether or not, and when, to have children
- pursue a satisfying, safe and pleasurable sexual life.
Human sexual response
Masters and Johnson published their groundbreaking book in 1966: 'Human Sexual Response'. It's based on clinical research proposing a linear model of sexual response for men and women.
Summary of Masters and Johnson's Human Sexual Response Cycle
Adapted from Katz. A, (2007. p10-15) 
Sexual therapist Helen Singer Kaplan then included the concept of desire to this model and condensed the response into 3 phases: desire, arousal and orgasm.
Both frameworks have since been criticised, because they don't account for non-biological experiences, such as pleasure and satisfaction. They don't place sexuality in the context of the relationship and assume men and women have similar sexual responses.
They also assume a linear progression from an initial awareness of sexual desire to one of arousal. They focus on genital swelling and lubrication through to orgasmic release and resolution. 
One of the most common causes of sexual dissatisfaction between couples is 'desire discrepancy', where one partner desires more sexual activity than their partner.
Alterations in sexual health or sexual dysfunction can be understood in different ways.
For example, to a non-professional, sexual alterations may be:
- a change in the person's perceptions of themselves or their body image
- a change in their physical functioning
- a change to their intimate relationships.
The World Health Organization (WHO) defines sexual dysfunction as 'the various ways in which an individual is unable to participate in a sexual relationship … he / she would wish'. 
Experiencing sexual dysfunction is relatively common in the community.
One large survey of Australian women reported that 70% experienced sexual difficulties (including the inability to orgasm and not feeling like sex) in the year before the survey.
Women over 50 were most likely to experience sexual difficulties, although they were common in all age groups (over 60% of women aged over 50 reported lack of interest in sex, and more than half of women aged 16-49 also reported this difficulty). 
From a biomedical perspective, 'sexology' refers to the scientific study of human sexuality.
It's the bio-medical approach to the study of human sexual behaviour and focuses on function and dysfunction.
In the past, sexologists focused primarily on human reproduction and sexual health as topics for learning and research. They also focused on the outcomes of sex, rather than the experience of sexuality.
Today, this is a growing area of research interest and includes the study of:
- human sexual response
- sexual emotions
- sexual function
- human relationships
- sexual pleasure
- sexual changes throughout life
- sexual diversity.
Sexual disorders ‒ the DSM-IV Classification
- American Psychiatric Association: DSM-IV: Diagnostic and Statistical Manual, 4th edition, 1994.
- World Health Organization: International Statistical Classification of Diseases and Related Health Problems-10 (ICD-10), 1992.
The DSM-IV Classification focuses on psychiatric disorders and provides a ‘Consensus-Based Classification of Male and Female Sexual Dysfunction’ (CCFSD).
This classification defines a sexual disorder as a ‘disturbance in sexual desire and in the psychophysiological changes that characterise the sexual response cycle and cause marked distress and interpersonal difficulty.’
This classification system has come under scrutiny and criticism, because it focuses only on the psychiatric component of sexual disorders, and because it’s based on the Masters and Johnson and Kaplan linear model of the sexual response.
However, the classification improves on the older systems, because it includes both psychogenic and organic causes of desire, arousal, orgasm and sexual pain disorders.
The diagnostic system also includes the criterion of ‘personal distress’, stating a condition is considered a disorder only if a person is distressed by it. 
Male & female sexual & gender identity disorders
DSM-IV identifies the following male and female sexual and gender identity disorders:
- sexual desire disorders
- sexual arousal disorders
- orgasmic disorders
- sexual pain disorders
- gender identity disorder
- sexual dysfunction due to a medical condition
- sexual dysfunction NOS (not otherwise specified).
The first 4 categories from the DSM-IV and ICD-10 classifications structure the CCFSD system.
In this module, we focus on understanding female sexual disorders. However, a woman's experience of sexuality is closely linked to her partner's sexual health and wellbeing. Male sexual disorders should also be understood. Those wishing to learn more about male sexual disorders should access the following readings for more information. 
Diagnosis for females – definitions
- There are 2 types of sexual desire disorders:
- Hypoactive sexual desire disorder is the persistent or recurrent deficiency (or absence) of sexual fantasies / thoughts, and / or desire for or receptivity to sexual activity, causing personal distress.
- Sexual aversion disorder is the persistent or recurrent phobic aversion to and avoidance of sexual contact with a sexual partner, causing personal distress.
- Sexual arousal disorder is the persistent or recurrent inability to attain or maintain sufficient sexual excitement, causing personal distress. This may be expressed as a lack of subjective excitement, or genital (lubrication / swelling) or other somatic responses.
- Orgasmic disorder is the persistent or recurrent difficulty, delay in, or absence of attaining orgasm following sufficient sexual stimulation and arousal, causing personal distress.
- There are 3 types of sexual pain disorders, and all can cause personal distress:
- Dyspareunia is the recurrent or persistent genital pain associated with sexual intercourse.
- Vaginismus is the recurrent or persistent involuntary spasm of the musculature of the outer third of the vagina that interferes with vaginal penetration.
- Non-coital sexual pain disorder is the recurrent or persistent genital pain induced by non-coital sexual stimulation.
4 Women's sexual dysfunction: revised and expanded definitions
Author: Basson, R.
In: Canadian Medical Association Journal - Volume 172, Issue 10 (May 2005)
6 Sex in Australia: Sexual difficulties in a representative sample of adults
Authors: Richters J, Grulich, AE, Visser, RO, Smith, AM, Rissel, CE (2003).
In: Australian and New Zealand Journal of Public Health Volume 27, Issue 2 , Pages164-170.
7 Google books - Diagnostic and Statistical Manual of Mental Disorders.
Fourth Edition (DSM-IV)
In: American Psychiatric Association, Washington, D.C., 1994.
(please note pp 539 - 545 unavailable in some limited previews)
12 Definitions of women's sexual dysfunction reconsidered: Advocating expansion and revision
Authors: Basson R, Leiblum S, Brotto L, Derogatis L, Fourcroy J, Fugl-Meyer K, Graziottin A, Heiman JR, Laan E, Meston C, Schover L, van Lankveld J, Weijmar Schultz W. (2003).
In: Journal of Psychosomatic Obstetrics & Gynecology, Vol. 24, No. 4, Pages 221-229
13 Report of the International Consensus Development Conference on female
sexual dysfunction: definitions and classifications
Authors: Basson R, Berman J, Burnett A, et al.
In: J Urol 2000;163:888-893.
15 Talking About Sexuality, Body Image and Cancer: A Teaching Resource
for Health Professionals
The Cancer Council of New South Wales. Kings Cross, NSW: The NSW Cancer Council; 2002.