In light of known similarities between substance-use disorders and behavioral disorders like gambling, this study, conducted by neuroscientists at Cambridge University and others, looked for similarities or differences between compulsive sexual behavior (CSB) and substance-use disorders by examining the role of “cue-reactivity” in CSB.

Cue Reactivity Explained

Individuals with substance addictions frequently show specific responses when confronted with substance-related cues³ (also referred to as stimuli). Such cues/stimuli may be visual, tactical, olfactory, or affect body’s sense of motion and equilibrium.⁴ Cue-reactivity is the process by which certain stimuli become associated with the rewarding properties of an addiction, eliciting a conditioned emotional or motivational reaction.⁵ In popular terms, this reaction is often referred to as wanting or craving. For instance, “the smell of cigarettes, places or friends associated with drug use, or the sight of money may act as conditioned cues and may enhance reactivity and trigger cravings”⁶ among drug users. People with substance-use disorders may also seek a substance because they want it, rather than enjoy it or like it; this phenomenon is known as incentive motivation, a major addiction theory.⁷

This heightened reactivity to cues may reflect “classical conditioning” in which neutral stimuli, after repeated pairing with rewarding stimuli, eventually elicit a conditioned response.⁸ This process not only provides the basis for the experience of craving and reward anticipation, but also the occurrence of withdrawal symptoms when the substance is not consumed.⁹ As has been demonstrated by quantitative meta-analysis, increased cue-reactivity is also related to relapse in substance-use disorders.¹⁰ Lastly, numerous studies using fMRI have demonstrated substance-related cue reactivity in regions of the brain including the prefrontal cortex, the anterior cingulate cortex, the ventral striatum, the insula, the hippocampus, the amygdala, and the dopaminergic mesolimbic reward system.¹¹

Methodology

The subjects for this study were 19 heterosexual men with CSB (mean age=25.61 years) and 19 age-matched healthy volunteers. Individuals with histories of substance-use disorders, or who had a psychiatric disorder or other mental health problems were excluded from the study. Subjects underwent fMRI scans while viewing five types of videos: sexually explicit (i.e., people engaged in consensual, heterosexual sexual interactions), erotic (e.g., dressed woman dancing erotically), non-sexually exciting (e.g., skiing, skydiving), money (e.g., coins or money being paid), and neutral (e.g., landscapes). Subjects responsed to a question about the images on a keypad. This allowed researchers to analyze responses in specific neural regions as they processed sexual cues. After viewing the video clips in the scanner, participants watched the videos again and were asked to rate them for the level of sexual desire (wanting) they felt after watching them, as well as how much they liked videos.

Findings

• Greater Internet and SEM Use: The CSB group reported greater Internet use than healthy controls. Additionally, CSB subjects reported using 25.5% of their total online use for viewing sexually explicit material (SEM, i.e., pornography) compared to 4.5% in healthy volunteers.
• Sexual and Erectile Dysfunction: Compared to healthy volunteers, subjects with CSB— whose average age was 25— reported more difficulty with sexual arousal and erectile problems in intimate relationships, but not with pornography, and first viewed online pornography at an earlier age.
• Excessive Pornography Use Despite Negative Consequences: Individuals with CSB (n=19) reported excessive use of pornography and all reported masturbation in conjunction with its use. Use of persons in prostitution via “escort services” (N=4) and “cybersex” (n=5) was also reported. Ten of these subjects had been or were currently in counseling for their behaviors. Several negative consequences of pornography use were reported by the CSB group, including the following:
  • losing jobs due to use at work (n=2)
  • damaging intimate relationships or negatively influencing other social activities (n=16)
  • experiencing diminished libido or erectile function (n=11)
  • engaging in excessive buying of sex from persons in prostitution (i.e., using “escorts”) (n=3)
  • experiencing suicidal ideation (n=2)
  • spending large amounts of money (n=3)
• Younger Age Associated with Greater Activation of Ventral Striatum: For both the healthy and especially the CSB group, the younger the individual the greater the activity in the ventral striatum in response to pornography. As Dr. Voon herself explained, this finding has important implications: “The frontal control regions of the brain—essentially, the ‘brakes’ on our compulsivity—continue to develop into the mid-twenties and this imbalance may account for greater impulsivity and risk taking behaviours in younger people.”¹²
• Dissociation between Desire and Liking: Subjective ratings of sexual desire (wanting) and liking of sexually explicit cues were disassociated among the CSB group, meaning that the CSB group had higher sexual desire ratings, but similar liking ratings, for sexually explicit videos compared to the healthy control group. In other words, the sexually explicit videos created a higher craving response in the CSB group, even though they did not strongly like the videos. Persons with CSB also had greater sexual arousal and erectile difficulties with partners, but not with SEM. These findings highlight that the higher sexual desire scores among those with CSB were specific to the explicit sexual cues and were not the result of the CSB subjects having higher libidos/sex drive.
• Exposure to sexually explicit cues was associated with greater activation of key brain regions associated with substance addictions¹³ in both groups, but more strongly activated and linked to sexual desire, and not liking, in the CSB group. This finding is in line with incentive-salience theories of addiction which have found enhanced wanting, but not liking, of salient rewards and indicates neurobiological similarities among compulsive sexual behavior and substance use disorders.