Algolagnia

Algolagnia (/ælɡəˈlæɡniə/; from Greek: άλγος, algos, "pain", and λαγνεία, lagnia, "lust") is a sexual tendency which is defined by derivingsexual pleasure and stimulation from physical pain,often involving an erogenous zone.
Studies conducted indicate differences in how the brains of those with algolagnia interpret nerve input
Currently, most psychological researchers feel that algolagnia is a physical phenomenon in which the brain interprets pain signals as pleasurable leading to psychological effects. In particular, the research conducted by Dolf Zillmann indicated that:
This, along with other research, often links algolagnia to aggression, or hypersexuality, or other control psychoses.
More recently, modern researchers using MRI and computer models of neuron firing patterns show that most algolagniacs experience pain differently from others. Algolagniacs may have DNA errors such as SCN9A, causing inaccurate nociception to occur.
At least one researcher in the 1900s (Albert Freiherr von Schrenck-Notzing, who was a self-professed sadist) thought that algolagnia was a psychological disorder, however this view began to change once the Kinsey Reports noted that many seemingly normal people often enjoy pain in a sexual context, and later Norman Breslow found that, before 1977, only four previous studies in all the scientific literature were empirical in nature. One of the researchers whom Breslow cited as having empirically-valid work, Andres Spengler, concluded that earlier research was "heavily burdened with prejudice and ignorance" against those whose sexual practices were in the minority, falsely assuming behaviors to be pathological when they were actually abnormal but harmless. Thomas Wetzstein also conducted a large-scale study of his local subculture from a sociological viewpoint, confirming Spengler's results and expanding on them.
No empirical study has found a connection to violent crimes or evidence for an increased tendency towards any sociopathological behavior in algolagnia or the related features of sexual sadomasochism, as had been generally assumed since Krafft-Ebing's era. The term algolagnia has since fallen into rare usage, and there is no entry for it in the American Psychiatric Association's DSM IV-TR, however inflicting pain on others has been termed "active algolagnia" and equated to the pathological form of sadism in Mosby's Medical Dictionary, which also equates the pathological form of masochism to "passive algolagnia",however it cannot be a pathological (dangerous) paraphilia form of sadism or masochism unless it involves pain inflicted on "non-consenting" persons or animals, or "cause[s] marked distress or interpersonal difficulty." And using algolagnia as both a pathological and non-pathological term, some in the modern research community still link it to some but not all BDSM activities.
Very little ongoing research has been conducted, with most nerve researchers focusing on nerve diseases and most physioneurologists concentrating on neuropathological reasons for such reactions.