Jaapl.org

Double-blind, Placebo-controlled Trial
of Sildenafil in Phallometric Testing
Nathan J. Kolla, MD, MA, MSc, Philip E. Klassen, MD, Michael E. Kuban, MSc,Thomas Blak, BA, and Ray Blanchard, PhD Not all males undergoing phallometric testing for assessment of deviant sexual interests respond adequately to teststimuli. As poor response may be linked to hormonal, neurologic, vascular, or psychogenic causes, we studied theability of sildenafil, an effective proerectile agent, to increase penile blood flow during phallometric testing.
Twenty-two males completed this double-blind, placebo-controlled trial of sildenafil (100 mg). Each participantunderwent phallometric testing with and without sildenafil. On average, each subject's peak response was 50percent greater in the sildenafil condition than it was in the placebo condition (p Ͻ.05). Correlations betweenparticipants' penile response to human stimulus categories, with or without treatment, were all very high (r ϭ0.77- 0.89) and statistically significant, thus indicating excellent reliability between the two test conditions. Theseresults support earlier findings that sildenafil significantly increases phallometric response among middle-agedmales. Moreover, pharmacologic treatment did not compromise the reliability of phallometric diagnosis.
J Am Acad Psychiatry Law 38:502-11, 2010
While patient-reported symptoms and behaviors are pubescents. In a recent study, penile plethysmogra- prerequisites for diagnosing virtually all mental dis- phy was used to discriminate hebephiles from pedo- orders, individuals with deviant sexual preferences philes.5,6 Clinical authorities recognize that not all are rarely forthcoming about their experiences.1,2 Pe- sex crimes against children are committed by pedo- dophilia is a psychiatric illness found almost exclu- philes or hebephiles.7 Some men who have a sexual sively in males and characterized by "recurrent, in- preference for adult women may molest children in tense" erotic interest in prepubescent children (Ref.
certain circumstances-for example, while they are 3, p 572). It has been alternatively defined as the under the influence of alcohol or drugs. Differenti- erotic orientation of individuals whose sexual attrac- ating between pedophilic and nonpedophilic sexual tion to prepubescent children exceeds their sexual offenders has important implications clinically, as attraction to physically mature adults.4 Less fre- sex-drive-reducing medications may be therapeuti- quently encountered in the literature is the term he- bephilia, which denotes a preferential attraction to Certain types of sexual offenses, in particular crimes involving younger, male, multiple, and ex- Dr. Kolla was a Resident in the Department of Psychiatry, Universityof Toronto, Toronto, Ontario, Canada, when the study was con- trafamilial victims, make a diagnosis of pedophilia in ducted. He is currently a Fellow in the New York University School of perpetrators more likely.9 While these variables in- Medicine Forensic Psychiatry Fellowship Program, New York, New crease the probability of sexual reoffending in men York. Dr. Klassen is Vice President of Medical Affairs at OntarioShores Centre for Mental Health Sciences, Whitby, Ontario, Canada; with a history of child molestation,10 sexual arousal and Assistant Professor of Psychiatry, Faculty of Medicine, University in response to children as measured by phallometry of Toronto, Toronto, Ontario, Canada. Mr. Kuban is Research Coor-dinator, and Mr. Blak is Research Analyst, Law and Mental Health remains the single best predictor of sexual recidi- Program, Centre for Addiction and Mental Health, Toronto, Ontario, vism.11 Most men presenting for psychiatric assess- Canada. Dr. Blanchard is Head, Clinical Sexology Services, Law andMental Health Program, Centre for Addiction and Mental Health, ment following charges or convictions of sexual of- Toronto, Ontario, Canada; and Professor of Psychiatry, Faculty of fending against children deny an erotic attraction to Medicine, University of Toronto, Toronto, Ontario, Canada. Thisresearch was supported by a grant from the American Academy of minors.12 In these instances, the patients' accounts of Psychiatry and the Law Institute for Education and Research to the their symptoms and behavior must be weighed first author. Address correspondence to: Nathan J. Kolla, MD, MA,MSc, Centre for Addiction and Mental Health, 250 College St., To- against the likelihood of their giving false informa- ronto, ON, Canada M5T 1R8. E-mail: nathan.kolla@utoronto.ca.
tion to avoid legal prosecution if they have indeed Disclosures of financial or other potential conflicts of interest: None.
committed a crime. A classification procedure that The Journal of the American Academy of Psychiatry and the Law
Kolla, Klassen, Kuban, et al.
can reliably determine erotic preference without re- ation of the corpus cavernosa smooth muscle. Its lying on patient-reported symptoms is therefore a mechanism of action involves competitive inhibition useful adjunct to the clinical assessment of sexual of the intracellular metabolic enzyme phosphodies- terase five (PDE5). One of the functions of PDE5 is The phallometric test is a psychophysiological tool to degrade the second-messenger molecule cyclic used to assess the erotic age and gender preferences of guanosine monophosphate (cGMP), which pro- adult males. Volumetric phallometry measures par- motes smooth muscle relaxation. Therefore, silden- ticipants' penile blood volumes under controlled afil sustains an erection by minimizing the destruc- conditions in a laboratory setting while they are ex- tion of cGMP.19 It is a safe medication that is well- posed to a standardized set of sexually themed stimuli depicting adults and children. Increases in penile Our research group recently found that low-dose blood volume serve as markers for the individuals' sildenafil increases the peak response during phallo- relative attraction to the different categories of per- metric testing among middle-aged males.21 Partici- sons. While Diagnostic and Statistical Manual of pants who received 50 mg of sildenafil before testing Mental Disorders, Fourth Edition, Text Revision showed a significant increase (28%) in phallometric (DSM-IV-TR) criteria for pedophilia do not include response compared with those tested without the results of phallometric testing,3 a phallometric clas- agent. These results prompted us to examine the ef- sification of pedophilia makes a diagnosis of pedo- fect of a larger dose of sildenafil on phallometric re- philia more likely in men who have sexual offenses sponse, by utilizing a more rigorous experimental against children but repudiate any erotic interest in design. Similar to our previous study, we purposely them. Several reviews have addressed the use of phal- selected a sample with characteristics that would bias lometric testing in clinical assessment.13-15 Recent against finding a significant association between drug studies suggest that phallometry may be able to de- treatment and increased response. For example, we tect the presence of deviant erotic interests in sexual restricted participation to men between the ages of offenders with developmental disabilities16 and juve- 45 and 60 years, in the knowledge that sildenafil is more effective in treating younger versus older males Blanchard and colleagues18 reported that the sen- with erectile dysfunction (ED).22 Participants were sitivity of our phallometric laboratory in classifying largely unemployed men living in shelters who had as pedophiles men who were accused of committing the leisure time to volunteer for the study. Our study sexual crimes against prepubescents but claimed a was not designed to test the question of whether preferential attraction to adult women was 61 per- sildenafil may cause deviant phallometric responses cent. This result was predicated on the assumption in the laboratory. Rather, we hypothesized that ad- that males who lacked charges against adults and pre- ministering 100 mg of sildenafil before phallometric sented with the greatest number of extrafamilial child testing would increase the response, at least to the victims (Ն3) were most likely to be true pedophiles; level observed with the lower dose, even under dou- among the 59 men accused of sexually offending ble-blind, placebo-controlled conditions.
three or more extrafamilial child victims in this sam-ple, 36 (61%) were phallometrically classified as hav-ing a pedophilic orientation. The phallometric test detected the lowest rates of pedophilia among males This study was approved by the Research Ethics with only one extrafamilial child victim. Data also Board at The Centre for Addiction and Mental revealed that 16 percent of their original sample had Health. Males between the ages of 40 and 65 years clinically uninterpretable phallometric test results who responded to recruitment advertisements due to a host of factors, including inadequate penile posted in our hospital and other research centers response. As uninterpretable phallometric results can were eligible to participate. The recruitment posters compromise the test's utility, it is incumbent on re- indicated that study investigators were interested in searchers to investigate any intervention that could testing the effect of sildenafil on sexual arousal in ameliorate an insufficient response.
males. Potential participants were encouraged to Sildenafil is a proerectile agent that has been contact the lead investigator (N.J.K.) for more shown to increase penile tumescence through relax- Volume 38, Number 4, 2010
Sildenafil in Phallometric Testing
We designated the following as exclusion criteria the participant's system. Participants were given the for the study: inability to speak or understand En- opportunity to discuss their phallometric results and glish; presence of psychotic disorder; legal blindness receive counseling from the clinician-investigators if or deafness; IQ Ͻ 70; serious cardiac, hepatic, oph- they wished; they were compensated $120 CAD for thalmic, or renal illness, as determined by history, physical examination, or laboratory investigations; Our phallometric laboratory was equipped for history of priapism; current use of sildenafil or other volumetric plethysmography. The main components PDE5s; allergy to sildenafil or other PDE5s; lactose included a glass cylinder that fit over the penis and intolerance (both drug and placebo capsules were segregated the air inside the cylinder from the outside compounded with lactose); current use of nitrates or atmosphere. A rubber tube was attached to the cyl- other medications known to interfere with the me- inder and connected to a pressure transducer, which tabolism of sildenafil; and current residence in a converted differences in air pressure to voltage-out- household with children. This last criterion was im- put changes. Increases in penile volume compressed posed to preclude any obligation on the part of the the air inside the cylinder, producing an output sig- study investigators to inform the necessary authori- nal from the transducer. The apparatus was cali- ties should participants' self-report and phallometric brated so that known quantities of volume displace- data suggest that they presented a danger to children.
ment in the cylinder (2 cubic centimeters (cc)) Potential participants who cared for other vulnerable corresponded to known changes in transducer volt- populations, including older members of society, age output. This instrument is highly sensitive and were not excluded, as gerontophiles (individuals with can reliably detect changes in penile blood volume a sexual preference for the elderly) are extremely rare much less than 1 cc. Readers are referred to Blan- and our phallometric apparatus does not include chard et al.18 for specific details on the phallometric stimuli to test for the presence of gerontophilia.
Two participants reported charges and/or admis- First, the examinee put the glass cylinder over his sions of criminal sexual behavior perpetrated against penis, according to instructions from the test admin- females age 17 or older. No attempt was made to istrator. He then sat in a reclining chair that faced corroborate the participants' self-reported legal his- three adjacent projection screens and put on a set of tories by accessing law enforcement agency data- headphones. Following this setup, the examinee's bases. Participants completed a standardized proto- lower body was draped with a sheet to minimize any col form used in our laboratory, which included embarrassment. The examinee's face was monitored questions about the gender and age of persons to by a low-light video camera during the test to detect whom participants were most sexually attracted, as stimulus avoidance strategies, such as closing the eyes well as their lifetime number of sexual partners.
or averting them from the test stimuli. Stimuli in- All participants received a complete history and cluded audiotaped narratives delivered through the physical by a physician investigator in addition to headphones, which corresponded with slides shown routine blood work, urinalysis, and electrocardio- on the projection screens. The visual stimuli in- gram. Participants served as their own controls for cluded images of nude pubescent and prepubescent the study. Sildenafil 100 mg or a placebo capsule boys and girls. These models were photographed identical in appearance to the compounded drug was circa 1970 after their parents signed written consent dispensed to each participant one hour before the forms granting permission for the pictures to be used first phallometric testing session; before the second in clinical and research activities involving penile session, the other agent was administered. Although plethysmography at our institution. These stimuli both subjects and study investigators were blind to have been used in over 10,000 phallometric tests in the identity of the drug or placebo and to the order in our laboratory. No child or adolescent model has which the participants received them, the capsules ever returned as an adult requesting the removal of were delivered to the investigators in randomized their photos from the phallometric protocol.
batches, such that half of the participants received the There were seven categories of narratives that de- drug first and half received placebo first. Testing ses- scribed sexual interactions with prepubescent girls, sions were separated by at least 48 hours to ensure pubescent girls, adult women, prepubescent boys, that drug metabolites were sufficiently cleared from pubescent boys, and adult men as well as solitary, The Journal of the American Academy of Psychiatry and the Law
Kolla, Klassen, Kuban, et al.
nonsexual activities (i.e., neutral stimuli). All narra- erally necessary when combining data from different tives were written in the second person and present examinees, as the interindividual variability in abso- tense. The narratives describing heterosexual interac- lute magnitude blood volume changes can obfuscate tions were recorded with a woman's voice, while even quite reliable statistical effects. There are nu- those describing homosexual interactions were re- merous sources of such variability, including the ex- corded with a man's voice. Neutral stimuli were re- aminee's age, his state of health, the size of his penis, corded with voices of both sexes. The specific test and the amount of time since his last ejaculation used in this study has been described in detail from masturbation or interpersonal sexual activity.
Empirical research has shown the z-score transforma- Each trial consisted of one narrative accompanied tion to be optimal.23,24 Second, the highly correlated by photographic slides on three adjacent screens that area and extremum z-scores are averaged to obtain a simultaneously projected the front view, rear view, composite that reflects both the speed and amplitude and genital region of a nude model who corre- of response and lessens the impact of anomalous re- sponded in age and gender to the topic in the narra- sponses, that is, large change from initial value but tive. Individual trials included three such models pre- sented for 18 seconds each. The total duration of a In the last stage of basic processing, the data were trial was therefore 54 seconds, during which the ex- reduced to seven final scores for each examinee by aminee viewed a total of nine slides, three at a time.
computing the mean of his four composite scores for Neutral narratives were similarly accompanied by each of the seven stimulus categories. These seven slides of landscapes. The full test consisted of four category scores were then taken as measures of the blocks of seven trials with each block containing one examinee's relative erotic interest in adult women, trial of each type (e.g., adult female) in pseudoran- pubescent girls, prepubescent girls, and so forth.
Another parameter measured in our laboratory Although the length of the trials was fixed, the was the amount of penile response (as opposed to the interval between trials varied, since penile blood vol- direction of response). This parameter was quanti- ume had to return to its baseline (flaccid) value be- fied as the mean of the three greatest penile responses fore a new trial could be initiated. The time needed to stimuli in any category (excluding neutral). The to complete a test was between one and two hours, observed quantity is called the output index,25 which with and without sildenafil. Recording of penile was expressed in milliliters of penile blood volume blood volume began five seconds before trial onset increase, beginning at trial onset. In clinical assess- and ended five seconds after trial offset. The pre- and ment and in some types of research, the output index post-trial data were not included in any calculations; is used to identify examinees whose penile blood vol- hence, the trial response did not reflect recovery (de- ume changes during the test trials remain within the tumescence) rates. Penile blood volume changes were range typical of random blood volume fluctuations sampled four times per second. The examinee's re- in nonaroused participants, and the phallometric sponse was quantified in two ways: as the extremum data of examinees who fail to meet the criterion out- of the curve of blood volume change (the greatest put index of 1.0 cc are excluded. In studies that focus departure from initial value occurring during the 54 on the absolute magnitude of penile response,26 seconds of the trial) and as the area under the curve.
rather than the relative magnitude of penile response Each examinee's 28 extremum scores were then to specific stimuli classes, the output index is used as converted into standard scores based only on his own a key dependent variable, as opposed to a gating cri- extremum data; the same operation was carried out terion, and participants are not excluded on the basis on his area scores. Next, standardized extremum and area scores were combined to yield a separate com- Statistical analyses were performed with SPSS posite score for each of the 28 trials, using the for- (version 15.0). Except where noted, Student's t tests mula (z E ϩ z A)/2, where z E is the standardized extremum score for the ith trial and z A is the stan- dardized area score for the ith trial. These operations were performed for two reasons. First, in phallomet- Twenty-four participants began the study, of ric work, some transformation of raw scores is gen- which 22 completed the investigation. We aimed for Volume 38, Number 4, 2010
Sildenafil in Phallometric Testing
Table 1 Demographic and Sexual History Characteristics of
The overall mean output index for all participants Self-Reported Heterosexual and Homosexual Participants in the drug condition was 12.6 Ϯ 9.5 cc, whereas the overall mean output index for participants in the control condition was 10.3 Ϯ 8.3 cc. The difference (2.3 cc) was not statistically significant (t p ϭ.22). Figure 1 presents the sample means of the output indices for each stimulus category under both drug and placebo conditions. The stimulus category "adult of preferred sex" referred to the participants'self-reported erotic age preference. All participantshad indicated an erotic preference for adults at theoutset of the study. Thus, in the case of heterosexual a sample size of 24 participants, double that of our participants, the preferred stimulus category was previous open-label trial.21 One participant was adult females, while for homosexual participants, the forced to withdraw after he ejaculated during the first preferred stimuli were adult males. Conversely, the phallometric testing session; the second individual nonpreferred adult stimulus categories for heterosex- lost interest in the study and opted not to continue.
ual and homosexual participants were men and The average age of the sample was 48.9 Ϯ 6.8 years.
women, respectively. The nonadult stimulus catego- An independent-samples t test revealed that age did ries were similarly categorized on the basis of whether not significantly differ between heterosexual and ho- the target object was of the preferred sex or not. The mean penile response to adults of the preferred sex Details of the participants' sexual histories and was 2.6 cc larger in the drug condition than in the other demographic variables are summarized in Ta- placebo condition. This difference was greater than ble 1. Two of the homosexual participants estimated the above-reported difference in output index (2.3 having had 500 lifetime male sexual partners each.
While this number may appear excessive comparedwith the sexual habits of the general homosexualpopulation, research data indicate that a sizeable pro-portion of gay men frequenting baths, sex clubs, andgay bars report a very high number of indiscriminateand anonymous sexual encounters. For example, asurvey conducted of San Francisco gay men in 1983,when the risks of unsafe sexual practices in relation totransmission of HIV had already been widely publi-cized, found that 61.6 percent of men (n ϭ 400)visiting baths or sex clubs reported having had two ormore sexual encounters in the previous month, while17.3 percent of men (n ϭ 400) socializing in gay barsor clubs similarly admitted to having had at least twosexual encounters in the preceding month.27 Assum-ing that the monthly frequency of random sexualencounters remained relatively constant for many ofthese individuals over the intervening years, it wouldtake some gay men less than two decades to accumu-late 500 lifetime sexual partners. The mean age of ourstudy participants was nearly 50 years; therefore, a Figure 1. Mean output indices to human stimulus categories under
lifetime number of 500 sexual partners among our placebo and sildenafil conditions; Adult PS, adult of preferred sex; homosexual participants would not be an unex- Pubes PS, pubescent of preferred sex; Prepub PS, prepubescent ofpreferred sex; Prepub NS, prepubescent of nonpreferred sex; Pubes pected result, especially if these men first became NS, pubescent of non-preferred sex; Adult NS, adult of nonpreferred sexually active in their early twenties or younger.
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Table 2 Correlations (Pearson's r) Between Penile Responses to Stimulus Categories With Sildenafil and Placebo
cc); however, it was still nonsignificant (t patients or participants undergoing phallometric assess- ment. Classifying participants as pedo/hebephilic or To control for between-subjects variability in out- not involved using each participant's category scores put index, treatment effect was expressed as the per- (standardized blood volume changes to each of the centage increase in response for the sildenafil condi- seven stimulus categories) to compute a pedophilic in- tion relative to the untreated condition. This method dex.28 The pedophilic index was calculated as the high- of data transformation was used in our previous est of the four category scores for children (prepubes- open-label study of sildenafil and phallometric re- cent girls, pubescent girls, prepubescent boys, and sponse.21 Comparing the mean percentage increase pubescent boys) minus the higher of the two category against an expected value of zero, we found that sil- scores for adults (adult men and women). The cutoff denafil produced a 50 percent increase in response score for dichotomously classifying a participant as pe- (t ϭ 2.21, p ϭ.038). A 53 percent higher response dophilic or nonpedophilic was z Ͼ 0.25. That is, par- was observed in the first session compared with the ticipants with a pedophilic index score greater than 0.25 ϭ 2.38, p ϭ.027), suggesting that the were classified as having pedophilia, whereas those with effect of stimulus novelty (outcomes attributable to scores less than or equal to 0.25 were classified as not the novelty of the initial stimulus) was comparable having pedophilia. This threshold has been the stan- dard in our laboratory for over 15 years. Each partici- Table 2 includes the correlations between par- pant was classified twice: once using his phallometric ticipants' ipsatized penile responses to the seven data from the placebo condition and once using his data individual stimulus categories under placebo and their ipsatized penile responses to the same cate- There were 15 participants whose phallometric re- gories under sildenafil. With the exception of the sults provided identical classifications for both pla- neutral category, all correlations were very high in cebo and drug trials and also confirmed the partici- absolute terms and were statistically significant pants' self-reported teleiophilic orientation (an erotic (p Ͻ.001). Participants completed their two phal- preference for physically mature adults). Among the lometric testing sessions on average 5.4 Ϯ 4.2 days remaining 7 participants from the original sample of apart from one another (range ϭ 2-20 days). An 22, there were 4 self-reporting teleiophilic partici- independent-samples t test showed that time to pants whose phallometric results obtained under pla- completion of the two sessions did not signifi- cebo and drug conditions yielded identical deviant cantly differ between those who received drug classifications. These phallometric classifications treatment before the first phallometric session or were therefore at odds with the participants' self- reported preference for the mature physique. Three Because our data indicated that there were clas- of these participants were phallometrically classified sification inconsistencies between the results of as heterosexual hebephiles (individuals with an erotic some participants' two phallometric tests or be- age preference for pubescent females) with and with- tween the results of one of their tests and their out sildenafil administration. The fourth participant self-report, each participant was classified as pedo/ was twice classified as a homosexual hebephile (an hebephilic or not pedo/hebephilic using the Kurt individual with an erotic age preference for pubes- Freund Laboratory's routine classification rule12,18 for cent males). Hence, the phallometric results ob- Volume 38, Number 4, 2010
Sildenafil in Phallometric Testing
in phallometric response under the drug condition(t ϭ 0.08, p ϭ.94). This result suggests that silde- nafil was less effective in the group of "inconsistent"responders. A 51 percent higher response was ob-served during the first testing session in this group,which although less than the consistent responders,was marginally statistically significant (t ϭ 2.49, Discussion
The results of the present investigation replicated and expanded on our previous analysis of the effect ofsildenafil on phallometric response.21 Participantstaking sildenafil in the current study showed a 50percent increase in phallometric response comparedwith placebo. In our open-label study, we found that50 mg of sildenafil citrate increased peak responsesby 28 percent. Pharmacodynamic studies indicatethat drug dose is the best predictor of functional Figure 2. Mean percentage increase in peak responses for consistent
and inconsistent test responders during sildenafil treatment.
outcome among patients taking sildenafil for clinicalindications.28 That is, higher doses tend to be moreefficacious. Indeed, a dose-response study of silde- tained with sildenafil and with placebo were consis- nafil in adult males with ED showed that increased tent for 19 of the 22 participants. The final three doses resulted in more robust erectile function.29 It study participants had contradictory phallometric was therefore expected that the higher dose of silde- test results: two individuals were classified as teleio- nafil used in this study would yield an increased phal- philic under sildenafil and pedo/hebephilic under lometric response in participants compared with that placebo, while one participant was classified as pedo/ in the earlier investigation. In routine clinical prac- hebephilic with sildenafil and teleiophilic with placebo.
tice, a dose of 100 mg sildenafil is indicated for the Given the foregoing discrepancy between some participants' self-reported erotic orientation and Test reliability refers to the consistency of test their phallometric classifications, we evaluated sepa- measures across repeated experiments. If a test is rately the effect of the drug in men whose test results reliable, it will produce similar results in the same were fully consistent with their self-reported adult participant under identical conditions. Although preferences (n ϭ 15) and in men whose test results our study was not specifically designed to assess were not fully consistent with their self-reported the reliability of phallometric classification, our preferences (n ϭ 7). Similar to our previous analyses, data revealed a very high concordance between the drug effect and stimulus novelty were calculated as phallometric classifications obtained from the two percentage increases; observed values were compared separate tests for each participant. Our confidence against a test value of zero, using one-sample paired t in the test's reliability is bolstered by the fact that tests. As presented in Figure 2, the consistent partic- a high level of agreement between the phallometric ipants demonstrated a 73 percent increase in penile classifications obtained from both testing sessions was observed despite experimental manipulation effect of stimulus novelty, which equated to 53 per- (administration of sildenafil before one of the two cent higher penile response during the first testing tests). The strength of the correlations between session, was not statistically significant (t penile response to each of the stimulus categories p ϭ.11). Among the seven participants whose phal- under drug and placebo conditions provides an lometric results were inconsistent with their self- additional measure of the phallometric test's high report, there was a negligible two percent increase reliability. These results indicate that participants The Journal of the American Academy of Psychiatry and the Law
Kolla, Klassen, Kuban, et al.
responded with similar relative magnitudes to each been suggested that the volunteers in Freund and stimulus category during both tests. The one ex- Watson's study produced more pedophilic and he- ception was the neutral category, where the rela- bephilic diagnoses because there were more genu- tionship was not significant, because examinees do ine pedophiles and hebephiles among them.18 not respond and are not expected to respond with Thus, there is good reason to suspect that the four penile tumescence to photographs of landscapes; individuals in our study classified as hebephiles where there is no meaningful variability, there can be no meaningful correlation. Both consistent and inconsistent responders showed novelty effects to Because of the great variability in absolute mag- the phallometric stimuli. Demonstrating reliabil- nitude of phallometric response among partici- ity of the phallometric classification was a crucial pants, it is probable that the study was underpow- step in this investigation, as any interpretation of ered to detect a significant difference between the the increased penile response occurring under the mean output indices obtained under the control drug condition hinged on our being able to estab- and experimental conditions. However, the abso- lish that sildenafil did not distort the participants' lute magnitude of the increased response observed under sildenafil has potentially important clinical Eighteen percent of our participants self-identi- implications. The minimum threshold for making fied as homosexual. If these individuals had been a phallometric diagnosis in our laboratory requires randomly selected from men in the community, an output index of 1 cc. Recent empirical data we would expect approximately three percent of from our laboratory have in fact indicated that the sample to have had a homosexual orienta- phallometric classification (deviant or no deviant tion.31 Although none of our participants indi- sexual preference) was no better than chance when cated an erotic preference for the immature phy- a participant's output index failed to reach 1 cc.33 sique, we found that 4 of 22 participants were We found that peak response increased by about phallometrically classified as hebephilic from both 2.3 cc with drug treatment. Thus, the amount of tests, which appears rather high. While the true blood volume increase observed with 100 mg of prevalence of pedo/hebephilia in the general pop- sildenafil was more than twice the volume needed ulation is unknown, both conditions are thought to classify participants reliably using phallometry.
to be rare. The high prevalence of hebephilic par- Placed in a clinical context, these data suggest that ticipants in this study is consistent, however, with men whose output indices fell below the minimum that in prior research in men who volunteered to 1 cc level could well be converted to responders participate in phallometric investigations-men who are very unlikely to constitute a representative Our investigation was limited to studying older cross-section of males in the general population.
males; furthermore, most of the participants denied For instance, Freund and Watson32 reported a 97 having a forensic history. These sample characteris- percent specificity for obtaining a phallometric tics make generalizing our results to younger, foren- classification of pedophilia in men who had sexual sic populations difficult. We did not have adequate offenses against adult women and who also power to examine a potential order effect of the two claimed to be gynephiles (individuals with an conditions on phallometric response, nor were we erotic preference for mature adult women). Yet, able to test whether the interaction of phallometric the test's specificity for paid volunteers who simi- classification and condition (drug versus placebo) in- larly claimed a preferential attraction to adult fluenced response. However, it was never expected women was only 81 percent. The authors surmised that one small study could answer these questions.
that differences in test-taking attitudes between Future investigations involving larger samples of the offenders and volunteers may have accounted men with forensic histories would likely be able to for the discrepant results. An alternative explana- tion posits that the reduced specificity of the test in Peak response increased significantly during volunteers was an accurate reflection of an in- drug treatment in men who claimed a preferential creased prevalence of pedophiles in this group attraction to the mature adult physique and whose compared with the offender group. Indeed, it has self-reported erotic orientations agreed with their Volume 38, Number 4, 2010
Sildenafil in Phallometric Testing
phallometric data. Moreover, re-exposure to the 5. Blanchard R: Reply to letters regarding pedophilia, hebephilia, identical stimuli did not produce a significant and the DSM-V. Arch Sex Behav 38:331- 4, 2009 6. Blanchard R, Lykins AD, Wherrett D, et al: Pedophilia, hebe- diminution of response. In contrast, sildenafil ef- philia, and the DSM-V. Arch Sex Behav 38:335-50, 2009 fected virtually no increase in response among the 7. Barbaree HE, Seto MC: Pedophilia: assessment and treatment, in participants whose self-reported orientations were Sexual Deviance: Theory, Assessment, and Treatment. Editedby Laws DR, O'Donohue W. New York: Guilford Press, 1997, pp incongruent with their phallometric results. These findings are consistent with results outlined in a 8. Dickey R: The management of a case of treatment-resistant para- phallometric study of sex offenders that examined philia with a long-acting LHRH agonist. Can J Psychiatry 37:567-9, 1992 the correlation between peak response in individ- 9. Seto MC, Barbaree HE: A brief screening scale to identify pedo- uals with consistent phallometric classification re- philic interests among child molesters. Sex Abuse 13:15-25, 2001 sults and those with inconsistent classifications.33 10. Seto MC, Harris GT, Rice ME, et al: The screening scale for Similar to our investigation, participants under- pedophilic interests predicts recidivism among adult sex offenderswith child victims. Arch Sex Behav 33:455- 66, 2004 went phallometric testing on two different occasions.
11. Hanson RK, Bussie`re MT: Predicting relapse: a meta-analysis of This study did not involve the use of sildenafil. How- sexual offender recidivism studies. J Cons Clin Psychol 66:348 - ever, the authors found that participants with consistent 12. Freund K, Blanchard R: Phallometric diagnosis of pedophilia. J phallometric test results demonstrated a significantly greater peak response compared with men whose clas- 13. Harris GT, Rice ME: The science in phallometric measurement of sifications were inconsistent. This result remained sig- male sexual interest. Curr Dir Psychol Sci 5:156 - 60, 1996 nificant after controlling for participant response on the 14. Howes RJ: A survey of plethysmographic assessment in North 15. Launay G: The phallometric assessment of sex offenders: an up- The findings of the present study suggest that date. Crim Behav Ment Health 9:254 -74, 1999 the men most likely to benefit from sildenafil pre- 16. Reyes JR, Vollmer TR, Sloman KN, et al: Assessment of deviant sexual arousal in adult male sex offenders with developmental treatment in phallometric testing may be teleio- disabilities. J Appl Behav Anal 39:173- 88, 2006 philes prone to subthreshold response under nor- 17. Seto MC, Murphy WD, Page J, et al: Detecting anomalous sexual mal test conditions. Since the reliability of the interests in juvenile sex offenders. Ann NY Acad Sci 989:118 -30,2003 phallometric test was unaffected by administering 18. Blanchard R, Klassen P, Dickey R, et al: Sensitivity and specificity sildenafil to the true teleiophiles, one can appreci- of the phallometric test for pedophilia in nonadmitting sex of- ate the implications of using this drug to increase fenders. Psychol Assess 13:118 -26, 2001 the phallometric response in men suspected of be- 19. Seftel AD: Phosphodiesterase type 5 inhibitors: molecular phar- macology and interactions with other phosphodiesterases. Curr ing pedophiles but who are in actual fact teleio- philes who have an inadequate response to phallo- 20. Hatzimouratidis K: Sildenafil in the treatment of erectile dysfunc- metric stimuli at baseline. Our data also imply that tion: an overview of the clinical evidence. Clin Interv Aging1:403-14, 2006 participants with something to conceal, possibly 21. Kolla NJ, Blanchard R, Klassen PE, et al: Effect of sildenafil on an erotic attraction toward children, may be more penile plethysmography responding: a pilot investigation. Arch likely to resist the effects of sildenafil. This inter- pretation would, of course, require more research, 22. Monga M, Bettencourt R, Barrett-Connor E: Community-based study of erectile dysfunction and sildenafil use: the Rancho Ber- 23. Earls CM, Quinsey VL, Castonguay LG: A comparison of three methods of scoring penile circumference changes. Arch Sex Behav References
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