any sexual behaviour regarded as abnormal by society. The deviation may relate to the sexual object (as in fetishism) or the activity engaged in (for example, sadism and exhibitionism). The activity is sexually pleasurable.
The definition of what is normal varies with different cultures, and treatment is appropriate only when the deviation causes suffering. Some people may find that counselling helps them to adjust to their deviation. Others may wish for treatment to change the deviation: aversion therapy may be used, also conditioning normal sexual fantasies to pleasurable behaviour. The only helpful effect of drugs is to reduce sexual drive generally.
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sexual behavior or fantasy outside that which is morally, biologically, or legally sanctioned, often specifically one of the paraphilias.Medical dictionary. 2011.