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Sexual dysfunctions and paraphilic disorders are disorders of either disturbance of processes in sexual functioning (sexual dysfunctions) or sexual behavior(s) (paraphilic disorders). Human sexuality presents a very complex interaction of biology and psychology, which is reflected in complex physiological responses. A seemingly very simple event, such as erection, is regulated on the central nervous system and peripheral nervous system level, modified by various hormones, affected by vascular changes, and influenced by various expectations, interpersonal issues, and intrapsychic processes, not to mention the influences of medications and substances of abuse, the aging processes, diseases, and personal habits. Although there is a substantial body of literature on human sexuality in general and sexual dysfunctions and paraphilias in particular, good evidence-based literature on most aspects of these disorders is mostly lacking. The focus has definitely moved from psychology to biology and medicalization of human sexuality. The biological sciences, such as pharmacology, have contributed enormously to developments in this area. However, an exclusive focus on biology and medical aspects of human sexuality is unwarranted and may trivialize a very complex area of human behavior. Even the clearly "biological" treatment approaches to sexual dysfunction may fail in certain situations due to various psychological factors. Thus, we caution the reader to always consider all factors, biological and psychological, in making the diagnosis and in planning treatment. In most cases, the judicious combination of biological and psychological treatment approaches will yield the most satisfactory results.
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The diagnoses of sexual dysfunctions and paraphilic disorders are mostly descriptive; no diagnosis-specific tests or examinations are usually available. The classification of sexual dysfunctions was historically based on the notion of connected yet separate and clearly defined phases of the sexual response cycle—desire, arousal/excitement, orgasm, and resolution. However, this model of sexual response is not considered as truly reflecting the intricacies of female sexual response and thus has been replaced by a different, more complicated circular model. As the linearity of sexual response in women was abandoned, the entire classification/listing of sexual dysfunctions in DSM-5 was changed, and the dysfunctions are listed alphabetically. Sexual dysfunctions in males are still diagnosed according to impairments of one of the first three "phases" (no impairment of the resolution phase has been identified). In females (in a simplistic way of explanation), the former female desire and arousal are combined into the diagnosis of female sexual interest/arousal disorder, and the diagnosis of female orgasm disorder is kept. However, clinically these disturbances are not so clearly separated and frequently overlap or coexist (e.g., lack of libido with impaired erection or orgasm). In addition, the previous diagnoses of painful sexual dysfunctions of dyspareunia and vaginismus are replaced with a single diagnosis of genito-pelvic/penetration disorder; and sexual aversion has been removed as a full-fledged diagnosis (could be diagnosed as Other specified sexual dysfunction). Interestingly, the present classification defines and uses only one end of the sexual functioning spectrum, the "lack" of functioning (e.g., lack of libido), though imprecisely ...