Patients with algolagnia could lead normal lives, enjoy normal arousal sequences, and indulge in fairly normal sexual intercourse, but when exposed to sexual pain, were unable to control their reaction. One woman described it as being unable to prevent her arousal or subsequent orgasm due to pain, even if she was not aroused when it began. This and other research have linked algolagnia to aggression, hypersexuality, or other control psychoses. Research using MRI and computer models of neuron firing patterns has shown 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. 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 in fact they were statistically abnormal, but harmless. In 1993 Thomas Wetzstein published 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 fallen into rare usage, and there is no entry for it in the American Psychiatric Association's DSM IV-TR. 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", but 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."