Sexual dysfunction disorders may be classified into four categories: sexual desire disorders, arousal disorders, orgasm disorders and pain disorders.

Sexual arousal disorders were previously known as frigidity in women and impotence in men, though these have now been replaced with less judgmental terms. Impotence is now known as erectile dysfunction, and frigidity has been replaced with a number of terms describing specific problems that can be broken down into four categories as described by the American Psychiatric Association's "Diagnostic and Statistical Manual of Mental Disorders": lack of desire, lack of arousal, pain during intercourse, and lack of orgasm.

For both men and women, these conditions can manifest themselves as an aversion to, and avoidance of, sexual contact with a partner. In men, there may be partial or complete failure to attain or maintain an erection, or a lack of sexual excitement and pleasure in sexual activity.

There may be physiological origins to these disorders, such as decreased blood flow or lack of vaginal lubrication. Chronic disease can also contribute, as well as the nature of the relationship between the partners.

Additionally, the condition Post-Orgasm illness Syndrome (POIS) may cause symptoms when aroused, including adrenergic-type presentation; Rapid breathing, paraesthesia, palpitations, headaches, aphasia, nausea, itchy eyes, fever, muscle pain/weakness and fatigue.

From the onset of arousal, symptoms can persist for up to a week in patients.

The aetiology of this condition is unknown, however it is believed to be a pathology of either the immune system or autonomic nervous systems. It is defined as a rare disease by the NIH but the prevalence is unknown. It is not thought to be psychiatric in nature, but it may present as anxiety relating to coital activities and thus may be incorrectly diagnosed as such. There is no known cure or treatment.

Female sexual arousal disorder (FSAD) is a disorder characterized by a persistent or recurrent inability to attain sexual arousal or to maintain arousal until the completion of a sexual activity. The diagnosis can also refer to an inadequate lubrication-swelling response normally present during arousal and sexual activity. The condition should be distinguished from a general loss of interest in sexual activity and from other sexual dysfunctions, such as the orgasmic disorder (anorgasmia) and hypoactive sexual desire disorder, which is characterized as a lack or absence of sexual fantasies and desire for sexual activity for some period of time.

Although female sexual dysfunction is currently a contested diagnostic, it has become more common in recent years to use testosterone-based drugs off-label to treat FSAD. While drug companies are technically not allowed to market these drugs for off-label uses, sharing the information with doctors at CME conferences has proved to be an effective way to navigate around the FDA approval process.

Anorgasmia, or Coughlan's syndrome, is a type of sexual dysfunction in which a person cannot achieve orgasm despite adequate stimulation. In males, it is most closely associated with delayed ejaculation. Anorgasmia can often cause sexual frustration. Anorgasmia is far more common in females (4.7 percent) than in males and is especially rare in younger men. The problem is greater in women who are post-menopause.

The condition is sometimes classified as a psychiatric disorder. However, it can also be caused by medical problems such as diabetic neuropathy, multiple sclerosis, genital mutilation, complications from genital surgery, pelvic trauma (such as from a straddle injury caused by falling on the bars of a climbing frame, bicycle or gymnastics beam), hormonal imbalances, total hysterectomy, spinal cord injury, cauda equina syndrome, uterine embolisation, childbirth trauma (vaginal tearing through the use of forceps or suction or a large or unclosed episiotomy), vulvodynia and cardiovascular disease.

A common cause of situational anorgasmia, in both men and women, is the use of anti-depressants, particularly selective serotonin reuptake inhibitors (SSRIs). Though reporting of anorgasmia as a side effect of SSRIs is not precise, studies have found that 17–41% of users of such medications are affected by some form of sexual dysfunction.

Another cause of anorgasmia is opiate addiction, particularly to heroin.

About 15% of women report difficulties with orgasm, and as many as 10% of women in the United States have never climaxed. Only 29% of women always have orgasms with their partner.

HSDD was listed under the Sexual and Gender Identity Disorders of the DSM-IV. In the DSM-5, it was split into male hypoactive sexual desire disorder and female sexual interest/arousal disorder. It was first included in the DSM-III under the name inhibited sexual desire disorder, but the name was changed in the DSM-III-R. Other terms used to describe the phenomenon include sexual aversion and sexual apathy. More informal or colloquial terms are "frigidity" and "frigidness".

In the DSM-5, male hypoactive sexual desire disorder is characterized by "persistently or recurrently deficient (or absent) sexual/erotic thoughts or fantasies and desire for sexual activity", as judged by a clinician with consideration for the patient's age and cultural context. Female sexual interest/arousal disorder is defined as a "lack of, or significantly reduced, sexual interest/arousal", manifesting as at least three of the following symptoms: no or little interest in sexual activity, no or few sexual thoughts, no or few attempts to initiate sexual activity or respond to partner's initiation, no or little sexual pleasure/excitement in 75%-100% of sexual experiences, no or little sexual interest in internal or external erotic stimuli, and no or few genital/nongenital sensations in 75%-100% of sexual experiences.

For both diagnoses, symptoms must persist for at least six months, cause clinically significant distress, and not be better explained by another condition. Simply having lower desire than one's partner is not sufficient for a diagnosis. Self-identification of a lifelong lack of sexual desire as asexuality precludes diagnosis.

There are several subtypes of female sexual arousal disorders. They may indicate onset: lifelong (since birth) or acquired. They may be based on context: they may occur in all situations (generalized) or be situation-specific (situational). For example, the disorder may occur with a spouse but not with a different partner.

The length of time the disorder has existed and the extent to which it is partner- or situation-specific, as opposed to occurring in all situations, may be the result of different causative factors and may influence the treatment for the disorder. It may be due to psychological factors or a combination of factors.

Sexual maturation disorder is a disorder of anxiety or depression related to an uncertainty about one's gender identity or sexual orientation. The World Health Organization (WHO) lists sexual maturation disorder in the ICD-10, under "Psychological and behavioural disorders associated with sexual development and orientation".

Sexual orientation, by itself, is not a disorder and is not classified under this heading. It differs from ego-dystonic sexual orientation where the sexual orientation or gender identity is repressed or denied.

Normally, a human being is able to feel pleasure from an orgasm. Upon reaching a climax, chemicals are released in the brain and motor signals are activated that will cause quick cycles of muscle contraction in the corresponding areas of both males and females. Sometimes, these signals can cause other involuntary muscle contractions such as body movements and vocalization. Finally, during orgasm, upward neural signals go to the cerebral cortex and feelings of intense pleasure are experienced. People who have this disorder are aware of reaching an orgasm, as they can feel the physical effects of it, but they experience very limited or no sort of pleasure.

It can depend on one or more of several causes, including:

- Sexual inhibition

- Pharmacological inhibition. They include mostly antidepressant and antipsychotic medication, and the patients experiencing that tend to quit them

- Autonomic nervous system

- Prostatectomy - surgical removal of the prostate.

- Ejaculatory duct obstruction

- Spinal cord injury causes sexual dysfunction including anejaculation. The rate of being able to ejaculate varies with the type of lesion, as detailed in the table at right.

- old age

Anejaculation, especially the "orgasmic" variant, is usually indistinguishable from retrograde ejaculation. However, a negative urinalysis measuring no abnormal presence of spermatozoa in the urine will eliminate a retrograde ejaculation diagnosis.

Thus, if the affected man has the sensations and involuntary muscle-contractions of an orgasm but no or very low-volume semen, ejaculatory duct obstruction is another possible underlying pathology of anejaculation.

Anejaculation is the pathological inability to ejaculate in males, with ("orgasmic") or without ("anorgasmic") orgasm.

Puberty usually occurs from the ages of 10 to 16 years of age and varies between boys and girls with girls normally starting earlier than boys (Shiel, Stoppler 2012). During the time of puberty is when sexual maturation starts to occur. Numerous physical changes happen during the period of puberty. Girls start to develop breasts, have growth of pubic hair and eventually begin having menstrual cycles. Boys have an enlargement of testicles and penis, growth of pubic hair, deepened voices and muscular development. Along with physical changes during puberty there are many mental changes happening. During the adolescence stage of life, boys and girls start developing thoughts related to sexual identity and start to explore and experiment with sexual behaviors. This stage of life is when sexual maturation starts to develop and one’s gender identity and sexual orientation is being developed. This is a timeframe that can possibly become confusing for the youth going through this stage of adolescence. Feelings of frustration, anxiety or depression may occur. This could be the first signs of disorder during sexual maturation.

Sexual maturity is a natural progression during the pubertal stages of adolescence. It is the timeframe where youth explore and experience sexual thoughts, situations and behaviors which ultimately lead to the identification of their gender and sexual orientation. During this timeframe abnormal feelings and thoughts can affect the progression of maturity. These abnormal occurrences would be identified as sexual maturation disorder.

The ICD-10 defines fetishism as a reliance on non-living objects for sexual arousal and satisfaction. It is only considered a disorder when fetishistic activities are the foremost source of sexual satisfaction, and become so compelling or unacceptable as to cause distress or interfere with normal sexual intercourse. The ICD's research guidelines require that the preference persists for at least six months, and is markedly distressing or acted on.

Under the DSM-5, fetishism is sexual arousal from nonliving objects or specific nongenital body parts, excluding clothes used for cross-dressing (as that falls under transvestic disorder) and sex toys that are designed for genital stimulation. In order to be diagnosed as "fetishistic disorder", the arousal must persist for at least six months and cause significant psychosocial distress or impairment in important areas of their life. In the DSM-IV, sexual interest in body parts was distinguished from fetishism under the name partialism (diagnosed as Paraphilia NOS), but it was merged with fetishistic disorder for the DSM-5.

The ReviseF65 project has campaigned for the ICD diagnosis to be abolished completely to avoid stigmatizing fetishists. Sexologist Odd Reiersøl argues that distress associated with fetishism is often caused by shame, and that being subject to diagnosis only exacerbates that. He suggests that, in cases where the individual fails to control harmful behavior, they instead be diagnosed with a personality or impulse control disorder.

In a review of 48 cases of clinical fetishism, fetishes included clothing (58.3%), rubber and rubber items (22.9%), footwear (14.6%), body parts (14.6%), leather (10.4%), and soft materials or fabrics (6.3%). A 2007 study counted members of Internet discussion groups with the word "fetish" in their name. Of the groups about body parts or features, 47% belonged to groups about feet (foot fetishism), 9% about body fluids, 9% about body size, 7% about hair (hair fetish), and 5% about muscles (muscle worship). Less popular groups focused on navels (navel fetishism), legs, body hair, mouth, and nails, among other things. Of the groups about clothing, 33% belonged to groups about clothes worn on the legs or buttocks (such as stockings or skirts), 32% about footwear (shoe fetishism), 12% about underwear (underwear fetishism), and 9% about whole-body wear such as jackets. Less popular object groups focused on headwear, stethoscopes, wristwear, and diapers (diaper fetishism).

Disorders of sex development (DSD), sometimes referred to as disorders of sex differentiation or differences of sex development, are medical conditions involving the reproductive system. More specifically, these terms refer to "congenital conditions in which development of chromosomal, gonadal, or anatomical sex is atypical."

The term has been controversial, and research has shown that affected people experience a negative impact, with the terminology impacting choice and utilization of health care providers. The World Health Organization and many medical journals still reference DSDs as intersex traits or conditions. The Council of Europe, and Inter-American Commission on Human Rights have called for a review of medical classifications that unnecessarily medicalize intersex traits.

Symptoms of GD in children may include any of the following: disgust at their own genitalia, social isolation from their peers, anxiety, loneliness and depression. According to the American Psychological Association, transgender children are more likely to experience harassment and violence in school, foster care, residential treatment centers, homeless centers and juvenile justice programs than other children.

Adults with GD are at increased risk for stress, isolation, anxiety, depression, poor self-esteem and suicide. Studies indicate that transgender people have an extremely high rate of suicide attempts; one study of 6,450 transgender people in the United States found 41% had attempted suicide, compared to a national average of 1.6%. It was also found that suicide attempts were less common among transgender people who said their family ties had remained strong after they came out, but even transgender people at comparatively low risk were still much more likely to have attempted suicide than the general population. Transgender people are also at heightened risk for certain mental disorders such as eating disorders.

Gender dysphoria (GD), or gender identity disorder (GID), is the distress a person experiences as a result of the sex and gender they were assigned at birth. In this case, the assigned sex and gender do not match the person's gender identity, and the person is transgender. There is evidence suggesting that twins who identify with a gender different from their assigned sex may do so not only due to psychological or behavioral causes, but also biological ones related to their genetics or exposure to hormones before birth.

Estimated rates of those with a transgender identity range from a lower bound of 1:2000 (or about 0.05%) in the Netherlands and Belgium to 0.5% of Massachusetts adults to 1.2% of New Zealand high-school students. These numbers are based on those who identify as transgender. It is estimated that about 0.005% to 0.014% of people assigned male at birth and 0.002% to 0.003% of people assigned female at birth would be diagnosed with gender dysphoria, based on 2013 diagnostic criteria, though this is considered a modest underestimate. Research indicates people who transition in adulthood are up to three times more likely to be male assigned at birth, but that among people transitioning in childhood the sex ratio is close to 1:1.

Gender dysphoria is classified as a disorder under "dual role transvestism" in the 2017 ICD-10 CM. GID was reclassified to "gender dysphoria" by the DSM-5. Some transgender people and researchers support declassification of GID because they say the diagnosis pathologizes gender variance, reinforces the binary model of gender, and can result in stigmatization of transgender individuals. The official reclassification as gender dysphoria in the DSM-5 may help resolve some of these issues, because the term "gender dysphoria" applies only to the discontent experienced by some persons resulting from gender identity issues. The American Psychiatric Association, publisher of the DSM-5, states that "gender nonconformity is not in itself a mental disorder. The critical element of gender dysphoria is the presence of clinically significant distress associated with the condition."

The main psychiatric approaches to treatment for persons diagnosed with gender dysphoria are psychotherapy or supporting the individual's preferred gender through hormone therapy, gender expression and role, or surgery.

DSDs are medical conditions involving the way the reproductive system develops from infancy (and before birth) through young adulthood. There are several types of DSDs and their effect on the external and internal reproductive organs varies greatly.

A frequently-used social and medical adjective for people with DSDs is "intersex". Parents with DSD children and clinicians involved in DSD treatment usually try to make clear distinctions between biological sex, social gender, and sexual orientation. This helps reduce confusion about the differences between being intersex, being transgender, and being gay/lesbian.

The most common DSD is congenital adrenal hyperplasia (CAH), which results in a person with female (XX) chromosomes having genitals that look somewhat masculine. In mild cases CAH results in a slightly enlarged clitoris, while in more severe cases it can be difficult to decide (just by looking) whether a baby is male or female (this is called having ambiguous genitals). Nevertheless, if they are old enough to know the difference, most children with CAH think of themselves as girls. CAH is caused by a problem with the adrenal glands and is usually treated by taking a daily medication to replace or supplement the missing adrenal hormones. (When this adrenal problem occurs in people with male (XY) chromosomes, the result is over-masculinization and premature puberty).

Another common DSD is androgen insensitivity syndrome (AIS), which means that a person with male (XY) chromosomes does not respond to testosterone in the usual way. This results in a body that to some degree has a feminine appearance. In Complete Androgen Insensitivity Syndrome (CAIS) the result is a totally feminine appearance, including typical female breast development. Consequently, most young women with CAIS are unaware of their condition until the early teen years when they fail to menstruate. In the milder form, called Partial Androgen Insensitivity Syndrome (PAIS), the genitals can vary from mostly female to almost completely male. Some people with PAIS think of themselves as girls/women, others regard themselves as boys/men, and some consider themselves mixed-gender.

One of the more unusual DSDs is 5-alpha-reductase deficiency (5ARD). It is caused by a shortage early in life of an enzyme that activates testosterone. In this condition, a person with male (XY) chromosomes has a body that appears female before puberty. After puberty begins, other testosterone-activating enzymes become available and the body soon takes on a masculine appearance, with the scrotum and penis usually reaching typical or nearly-typical size. If 5ARD is diagnosed at a young age, the child is often raised as a boy (a 1996 Brazilian study suggested that the majority of adults with this condition consider themselves men but this has been questioned in some more recent research).

In addition to CAH, CAIS, PAIS, and 5ARD there are several rarer types of DSDs, and in some cases it is not possible to make a clear diagnosis of the underlying condition.

The penis and clitoris are essentially the same organ (differing only in size, and generically called the phallus). In typical males, the urethra is located at the tip of the penis, while in typical females the urethra is located below the base of the clitoris. When the phallus is of intermediate size, it is possible also to have a urethral opening located along the shaft; this condition is known as hypospadias.

Open-minded parenting, appropriate and conservative medical intervention, and age-appropriate child involvement in the treatment plan contribute greatly to successful outcomes for the entire range of DSDs.

Paraphilia (previously known as sexual perversion and sexual deviation) is the experience of intense sexual arousal to atypical objects, situations, fantasies, behaviors, or individuals. Such attraction may be labeled sexual fetishism. No consensus has been found for any precise border between unusual sexual interests and paraphilic ones. There is debate over which, if any, of the paraphilias should be listed in diagnostic manuals, such as the "Diagnostic and Statistical Manual of Mental Disorders" (DSM) or the International Classification of Diseases (ICD).

The number and taxonomy of paraphilia is under debate; one source lists as many as 549 types of paraphilia. The DSM-5 has specific listings for eight paraphilic disorders. Several sub-classifications of the paraphilias have been proposed, and some argue that a fully dimensional, spectrum or complaint-oriented approach would better reflect the evidence.

It is thought that people who suffer from this disorder, suffer from a dysfunction in the release of the chemical dopamine in the nucleus accumbens, the brain's primary reward center. This part of the brain is thought to play a role in pleasurable activities, including laughter, addiction, and music. Additionally, it is thought that depression, drug addiction, high levels of prolactin, low testosterone, and uses of certain medications might play a role in inhibiting dopamine. A spinal cord injury or chronic fatigue syndrome might also occasionally cause this disorder. Age may also be a cause of this disorder.

A sudden-onset sexual anhedonia can also be a symptom of sensory neuropathy, which is most commonly the result of pyridoxine toxicity (e.g., from large doses of vitamin B6 supplements).

In this case, the sexual dysfunction promptly resolves spontaneously once the B6 supplementation is stopped.

Increased serum prolactin (PRL) concentration in patients brains from psychiatric medicine can also affect sexuality.

Psychiatric medicine is known to cause the brain to form more dopamine receptors for the dopamine blocking effect. The normal amount of dopamine released during sex is insufficient to stimulate the larger number of dopamine receptors.

Young males are most often affected, though similar symptoms have been reported in females with excessive vaginal discharge or leucorrhea, which is also considered a "vital fluid".

Premature ejaculation and impotence are commonly seen. Other somatic symptoms like weakness, easy fatiguability, palpitations, insomnia, low mood, guilt and anxiety are often present. Males sometimes report a subjective feeling that their penises have shortened. These symptoms are usually associated with an anxious and dysphoric mood state.

Frotteurism is a paraphilic interest in rubbing, usually one's pelvic area or erect penis, against a non-consenting person for sexual pleasure. It may involve touching any part of the body, including the genital area. A person who practices frotteuristic acts is known as a "frotteur". Toucherism is sexual arousal based on grabbing or rubbing one's hands against an unexpecting (and non-consenting) person. It usually involves touching breasts, buttocks or genital areas, often while quickly walking across the victim's path. Some psychologists consider toucherism a manifestation of frotteurism, while others distinguish the two. In clinical medicine, treatment of frotteuristic disorder involves cognitive behavior therapy coupled with the administration of a SSRI.

The DSM-5 adds a distinction between "paraphilias" and "paraphilic disorders", stating that paraphilias do not require or justify psychiatric treatment in themselves, and defining "paraphilic disorder" as "a paraphilia that is currently causing distress or impairment to the individual or a paraphilia whose satisfaction has entailed personal harm, or risk of harm, to others".

The DSM-5 Paraphilias Subworkgroup reached a "consensus that paraphilias are not "ipso facto" psychiatric disorders", and proposed "that the DSM-V make a distinction between "paraphilias" and paraphilic "disorders". [...] One would "ascertain" a paraphilia (according to the nature of the urges, fantasies, or behaviors) but "diagnose" a paraphilic disorder (on the basis of distress and impairment). In this conception, having a paraphilia would be a necessary but not a sufficient condition for having a paraphilic disorder." The 'Rationale' page of any paraphilia in the electronic DSM-5 draft continues: "This approach leaves intact the distinction between normative and non-normative sexual behavior, which could be important to researchers, but without automatically labeling non-normative sexual behavior as psychopathological. It also eliminates certain logical absurdities in the DSM-IV-TR. In that version, for example, a man cannot be classified as a transvestite—however much he cross-dresses and however sexually exciting that is to him—unless he is unhappy about this activity or impaired by it. This change in viewpoint would be reflected in the diagnostic criteria sets by the addition of the word "Disorder" to all the paraphilias. Thus, Sexual Sadism would become Sexual Sadism Disorder; Sexual Masochism would become Sexual Masochism Disorder, and so on."

Bioethics professor Alice Dreger interpreted these changes as "a subtle way of saying sexual kinks are basically okay – so okay, the sub-work group doesn’t actually bother to define paraphilia. But a paraphilic disorder is defined: that’s when an atypical sexual interest causes distress or impairment to the individual or harm to others." Interviewed by Dreger, Ray Blanchard, the Chair of the Paraphilias Sub-Work Group, explained: "We tried to go as far as we could in depathologizing mild and harmless paraphilias, while recognizing that severe paraphilias that distress or impair people or cause them to do harm to others are validly regarded as disorders."

Charles Allen Moser pointed out that this change is not really substantive as DSM-IV already acknowledged a difference between paraphilias and non-pathological but unusual sexual interests, a distinction that is virtually identical to what is being proposed for DSM-5, and it is a distinction that, in practice, has often been ignored. Linguist Andrew Clinton Hinderliter argued that "Including some sexual interests—but not others—in the DSM creates a fundamental asymmetry and communicates a negative value judgment against the sexual interests included," and leaves the paraphilias in a situation similar to ego-dystonic homosexuality, which was removed from the DSM because it was realized not to be a mental disorder.

The DSM-5 acknowledges that many dozens of paraphilias exist, but only has specific listings for eight that are forensically important and relatively common. These are voyeuristic disorder, exhibitionistic disorder, frotteuristic disorder, sexual masochism disorder, sexual sadism disorder, pedophilic disorder, fetishistic disorder, and transvestic disorder. Other paraphilias can be diagnosed under the Other Specified Paraphilic Disorder or Unspecified Paraphilic Disorder listings, if accompanied by distress or impairment.

The professional handbook of the American Psychiatric Association (APA), the "Diagnostic and Statistical Manual of Mental Disorders", fifth edition, lists the following diagnostic criteria for "frotteuristic disorder".

- Over a period of at least 6 months, recurrent and intense sexual arousal from touching or rubbing against a nonconsenting person, as manifested by fantasies, urges, or behaviors.

- The individual has acted on these sexual urges with a nonconsenting person, or the sexual urges or fantasies cause clinically significant distress or impairment in social, occupational, or other important areas of functioning.

If the individual has not acted on their interest and experiences no distress or impairment, they are considered to have a frotteuristic sexual interest, but not frotteuristic disorder. Some sexologists distinguish between frotteurism (as pelvic rubbing) and toucherism (as groping with hands), but the DSM does not. Sexologist Kurt Freund described frotteurism and toucherism as courtship disorders that occur at the tactile stage of human courtship.