1. Psychosexual development

1.1. Biological determination of sexual development

Biological basis of sexuality is above all the sexual dimorphism, which is determined by chromosomal sex, gonadal differentiation, hormonal factors, inner reproduction organs and morphology of genitalia. On the chromosomal level, the male sex is distinguished by the genotype 46 XY, the female one by 46 XX, whereas the sexual chromosomes X and Y have the determinant impact on the forming process of initially undifferentiated primary gonades of the foetus. The feminisation end masculinisation of genitalia (which proceeds during the second and at the beginning of the third month of gravidity) is subject to hormonal regulation. The main determining factor of sexual differentiation is testosterone.

The psychosexual evolution of individuals is continuation of embryonal development of sexual structures - physical sexual development constitutes anatomic and functional background for sexual differentiation of behaviour, emotions and mind.

1.2. Determinants of psychosexual development

Development of sexual identification, sexual role, sexual preferences and sexual behaviour can be considered as the basic determinants of psychosexual development.

a/ Sexual identification

Sexual identity, i.e. the feeling of belonging to particular gender, is formed on the basis of genetic and prenatal (hormonal, gonadal) determinants mediated by the organising influence of sexual steroids on central nervous system during the second trimester of the intrauterine development. Its final forming proceeds then after the delivery due to the interaction of this predisposition and the environment. Forming of gender identity is probably mostly determined before the age of 18 months. The basis of sexual identification is a concept of self that is created in the learning process, especially social learning as well as cognitive learning, which is typical for human beings.

b/ Sexual role

Sexual role is the external display of gender identity. Although there are also constitutional factors participating in its formation, cultural and social influences, mediated mainly by family, play the decisive role. Parents are just the main identification figures for their child, important for the development of adequate behaviours as well as the attitudes towards the opposite sex. In the school age, the parental influence on the formation of the sexual role is complemented by the influence of peer groups and other cultural and social influences (school, media, etc.)

c/ Sexual preferences

The mechanism of the development of sexual preferences (the way an individual reaches sexual satisfaction and which objects erotically prefers) has not yet been fully resolved. Most probably, the constitutional factors are the basic ones. Genetic factors may i.g. determine the preparedness to respond to erotic signals of certain kind. Some role can be also credited to a specific "programming" of sexual centres during the crucial phases of prenatal development. Influences of environment assert probably themselves only on the basis of innate mechanisms.

The proof of importance of constitutional factors in the development of homosexual orientation can for example be represented by 40 - 60% concordance of homosexuals in enzygotyc (monozygotyc) twins or hormonal reaction of homoerotically oriented men to providing of oestrogens. Attempts to deduce homosexual orientation for example from familial constellation, defectivity of parental models or from other environmental influences have all failed so far. Similarly, all "therapeutic" (i.g. behavioristic, as aversion therapy, shame therapy etc.) procedures, centred on the change of sexual orientation, have not been successful.

Most disorders in the area of sexual preferences develop only during pubescence or adolescence. Although even in pre-pubertal period, we could observe for example cross-dressing in transvestites, preference of certain fetish during masturbation in fetishists, voyeuristic, exhibitionistic or other unusual sexual practices in individuals with differently deviant development of sexual motivation, it is only in pubescence that the content of sexual fantasies (of i.g. sadomasochistic, exhibitionistic or paedophile character) could show evidence of disorder in sexual preference in the sense of paraphilia.

d/ Sexual behaviour

Capability to genital reaction is present in human beings since babyhood. Genital stimulation together with orgasm was observed in boys and girls since their 6th month and the masturbation of children often persists as the predominant sexual activity until the beginning of partner sexual activities.. According to surveys, majority of boys and a significant percentage of girls are masturbating already in the pre-pubertal period, this behaviour only becomes, gradually with age, less and less visible, more intimate matter.

Sexual games are similarly frequent child activity that appears most often at about the age of five. In general, these are not of erotic character, they are only a display of children’s curiousness. These activities consist mainly in mutual exploration of intimate body parts, often include also imitation of sexual activities of adults, practically only in non-coital forms. Masturbation as well as these sexual games are absolutely natural and innocuous, on the contrary, forbidding or punishing them can have deteriorative impact on differentiation of gender identity and role.

In pubescence, there is an integration of gender identity, sexual reactivity and sexual preference. In our population, this happens between 1Oth and 15th year of age, physically girls experience menarche and boys the first ejaculations. Especially in boys this development is joined with an intense increase in sexual need and activity. Psychosexual development is delayed compared with the somatosexual one, in this period, the capability of young people of emotional romantic attachment, pair bonding or their moral and ethical values are only forming.

The development of sexual behaviour is contingent on the development of sexual emotions that are just formed mainly in pubescence and adolescence. It is a case of sexual arousal (whose physiological correlate for men is erection and for women lubrication), orgastic function and sexual satisfaction, and finally of the development of love attachment as an erotic fascination.

2. Sexual deviations (paraphilias)

From the sexological point of view, we can consider as normal such consensual sexual activities that take place between psychosexually and somatosexually mature enough and not lineally consanguineous partners and that do not lead to psychical and/or physical harm.

According to official International Classification of Diseases (ICD) published by WHO in the 10^th revision in1992, in the chapter "Mental and behavioural disorders", sexual deviations are included in the section "Personality and behavioural disorders" under code F 65 as "Sexual Preference Disorders", paraphilias. Paraphilias are, according to this classification, characterized by "sexual impulses, fantasies and practices that are unusual, deviant or bizarre". Following conditions belong among general diagnostic criteria of paraphilia as to ICD 10: a) an individual repeatedly experiences intensive sexual desires and fantasies concerning unusual objects and activities, b) the individual either satisfies his/her unusual desires, or is intensively bothered by them, c) the preference is present for at least 6 months.

Sexual deviations (paraphilias) are considered as qualitative sexual motivation system structure disorders. They include a wide range of activities, from harmless but socially difficult behaviour (indecent exposure, cross-dressing) to the most dangerous offences against human dignity, health or life of victims. Socially dangerous sexual deviations can turn out as sexual crime. It is however important to be aware of the fact that by far not all the sexual crimes are committed by deviant offenders (especially in the cases of rapes or sexual abuses of children the perpetrators are more often sociopathic, impulsive or aggressive psychopaths, alcoholics, socio-sexually immature individuals, mentally handicapped, to some extent also psychotics) and at the same time not all deviants commit sexual crimes.

It is very likely that the development of deviation is caused by innate (inborn) predisposition, whereas later circumstances - education, sexual experience, etc. - play only framing role. The exact mechanism of development of the deviant sexual preferences is however not known yet. Nevertheless, we are able, on the basis of specialized therapeutic programmes, to teach a patient to live with his/her disorder - which means above all that they do not harm their surroundings and find a suitable solution of their sexual needs. In some cases we are only able to suppress the patient’s sexuality to the level at which he/she is capable to manage his/her urges by will. The suppression can be attained by long-run administration of anti-androgens or some psychofarmacs reducing sexual appetence of a person, or - in exceptional cases and only upon patient’s request - also by surgical castration.

Basically, we distinguish two types of sexual deviances - deviations