An anaphrodisiac (also antaphrodisiac or antiaphrodisiac) is a substance that quells or blunts the libido. It is the opposite of an aphrodisiac, something that enhances sexual appetite. The word anaphrodisiac comes from the Greek privative prefix ἀν-, denoting negation, and aphrodisiac, from the Greek goddess of love, Aphrodite. Some people use anaphrodisiacs in order to curb a very high libido or due to hypersexuality. However anaphrodisiacs are also used by those with an average libido, at times due to having incessant schedules. Available anaphrodisiacs classes of substances Some common anaphrodisiacs are ethanol (alcohol) and tobacco, but this is typically an unintended consequence and not often the main reason for use. While alcohol is used socially because it initially reduces mental inhibitions, studies have shown that over time alcohol physically decreases arousal and makes achieving climax more difficult. For this reason alcohol is considered an anaphrodisiac. Opioids, a class of pain-reducing substances which include morphine, heroin, and hydrocodone, are anaphrodisiacs. Side effects of certain antidepressant medications commonly include those taking anaphrodisiac form (there is even a term for the phenomenon among one particularly notorious group— SSRI-induced sexual dysfunction); however, psychotropic drugs are not currently prescribed for reliable anaphroditic effects. Antiandrogens such as cyproterone acetate and medroxyprogesterone acetate, or the LHRH agonist leuprolide, are sometimes prescribed to convicted male sex offenders who are released on parole in an effort to stop them reoffending, in a treatment sometimes referred to as chemical castration, however the high doses required often cause a range of side effects which may limit compliance. Other antiandrogens such as finasteride and spironolactone may also lower sex drive, as can certain antipsychotics such as benperidol. Estrogens can act as anaphrodisiacs in men by suppressing testosterone production by the testicles. History Herbal anaphrodisiacs have been employed by various religious sects and orders throughout history. Barrister Sir Edward Marshall Hall theorised that murderer Hawley Harvey Crippen was using hyoscine on his wife as an anaphrodisiac but accidentally gave her an overdose and then panicked when she died. Various forms of anaphrodisiacs have been tried to cure hypersexuality in both humans and non-human animals. In both medieval history and modern times, anaphrodisiacs have been used as a tool intended to reduce the sex drive of sex offenders. Scientific study Studies have evaluated the effect of herbal anaphrodisiacs on men and women. These include studies on the effect of substances on both hormone levels