One of Canada’s leading sexual-offender experts, psychiatrist John Bradford, M.D., and his team conducted a 20-year study of almost 800 male sexual offenders and discovered that the gonadotrophic sex hormones luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were better predictors of recidivism than the sex hormone testosterone was.
“This study is an important one, with a surprising finding that gonadotrophic hormones were better predictors of recidivism for sexual crimes than testosterone,” Richard Krueger, M.D., told Psychiatric News. Krueger, an associate clinical professor of psychiatry at Columbia University College of Physicians and Surgeons, has conducted extensive research on sexual offenders. “Given the prominent role of testosterone in sexual function and in sexual and nonsexual aggression, studies that prospectively examine biological in addition to behavioral variables in humans are extremely important.”
Bradford, who is clinical director of the Forensic Treatment Unit of the Royal Ottawa Health Group in Ottawa, Canada, and colleagues included 771 adult male sex offenders in their study. About two-thirds were pedophiles, over 20 percent were exhibitionists, 10 percent were rapists of adult women, and the remainder had engaged in other forms of sexual offenses. The men had been evaluated between 1982 and 1996 at a university-affiliated forensic sexual behaviors clinic for levels of LH and FSH, total testosterone (testosterone bound to proteins in the blood), and free testosterone (testosterone not bound to proteins in the blood). Although only 2 percent of testosterone is free, it is believed that it is more active than total testosterone is.
Recidivism data for the subjects were obtained in 2002 from a national database maintained by the Royal Canadian Mounted Police. This means that some subjects had been observed for up to 20 years in the community; the average observation time was 11 years. The percentage of subjects who reoffended sexually during the follow-up period was 18 percent, the researchers found. Finally they assessed whether there were any links between subjects’ initial LH, FSH, or testosterone levels and their later recidivism.
LH and FSH levels were significantly associated with recidivism outcomes, whereas levels of total testosterone and free testosterone were not, Bradford and his team reported in the December 2012 Journal of the American Academy of Psychiatry and the Law.
As for their study’s implications, “Our results do not support the idea that abnormal hormone levels explain sexual offending,” the researchers said. “Instead, relatively high levels of LH and FSH must interact with other actors to increase the likelihood of sexual aggression.”
But what other factors might be involved? Perhaps hostility, the researchers suspect, because when they looked to see whether self-reported hostility and sex drive, which had been evaluated in the subjects during their initial assessment, mediated the effects of LH and FSH on recidivism, they found that only hostility—not sex drive—did.
Hostility had been evaluated with the Buss-Durkee Hostility Inventory, which measures seven aspects of hostility—irritability, suspicion, negativism, resentment, indirect hostility, verbal hostility, and physical assault. Rapists have scored high on this inventory in the past.
If these findings can be confirmed, they “suggest a new area of investigation in the neurobiology of sexual offending,” Bradford and his group suggested.
The study had no outside funding. ■