What was the purpose of the study?
Some clinicians describe patients who report problems decreasing their sexual behaviors, such as viewing many hours of sexual films online every day, as sexually “addicted” or “hypersexual”. Our study tested whether people who report such problems look like other addicts from their brain responses to sexual images. Studies of drug addictions, such as cocaine, have shown a consistent pattern of brain response to images of the drug of abuse, so we predicted that we should see the same pattern in people who report problems with sex if it was, in fact, an addiction.
What is the main finding in your study?
We found that the brain’s response to sexual pictures was not predicted by any of three different questionnaire measures of hypersexuality. Brain response was only predicted by a measure of sexual desire. In other words, hypersexuality does not appear to explain brain differences in sexual response any more than just having a high libido.
Does this prove sex addiction is a myth?
If our study is replicated, these findings would represent a major challenge to existing theories of sex “addiction”. The reason these findings present a challenge is that is shows their brains did not respond to the images like other addicts to their drug of addiction.
What exactly did your study do?
A large group of men and women attracted to the opposite sex who reported having problems controlling their viewing of sexual images had their brain responses measured using electroencephalography (EEG) while they viewed photographs. These photographs were carefully selected from a well-characterized set of images to evoke pleasant or unpleasant feelings. Some pictures included dismembered bodies, people preparing food, skiers, and sex.1
The sexual images included some romantic images of caressing, kissing and undressing, whereas others showed explicit intercourse between one man and one woman. We were most interested in the brain’s response starting about 300 milliseconds after the picture appeared, which is commonly called the “P300”. This basic protocol and measure have been used in hundreds of neuroscience studies internationally, including studies of addiction and impulsivity, and we followed the same standards for collecting and analyzing these data. For example, one study of heroin dependent men reported increased P300 response to images of heroin as compared to neutral images.2
What was your hypothesis?
We hypothesized that the P300 response to the sexual images would be predicted by a person’s sexual desire level, as this has already been reported by other scientists. We also predicted that measures of hypersexuality might relate positively or negatively to the P300. The direction (positive or negative) would depend on which model of hypersexuality (addiction or impulsivity) was a better model.
What does it mean that P300 and hypersexual measures were not related?
It suggests that hypersexuality explains nothing in particular about brain responses to erotica. It also might mean that the relationship is so small that we were not able to see it with our measures.
What is EEG and why did you use it?
There are many ways to measure brain responses. MRI and EEG are very common. We choose measures depending on what we want to study. While fMRI is better for finding where
something is occurring in the brain, EEG is better for finding when
something is occurring in the brain. EEG measures synchronous firing activity (some have estimated of 100,000 neurons) at the scalp. EEG can be used to make pretty brain pictures like fMRI, and fMRI can be speeded, but there are good reasons to have both tools.
I thought there were already brain studies of sex addiction?
Surprisingly, no one has previously examined their brain in action. A few research groups included “porn addicts” in brain imaging studies of internet use problems, but none of those researchers actually analyzed the sex group separately. A couple of research groups published small structural brain studies, which means images of the brain when it is not doing anything in particular. We have colleagues in Germany who are currently writing the first fMRI results of their hypersexual patients, so anticipate more research in this area soon.
Who volunteered for your study?
Our ethics board was very concerned that, if we recruited people actually seeking treatment for sex addiction, showing them sexual images could cause them to “relapse”. We agreed to recruit people who reported problems regulating their viewing of visual sexual stimuli. We confirmed that they had problems with three questionnaires that are commonly used to measure hypersexuality. In the end, our volunteers actually reported just as many problems as patient samples.
How do these volunteers compare to people who do not have problems? A control group?
This study only included people who reported problems, ranging from relatively minor to overwhelming problems, controlling their viewing of visual sexual stimuli. This means we used a within-subject design. A within-subject design means people serve as their own control. Within-subject designs can be a much more powerful design, statistically and theoretically, than having a separate control group. For example, with a separate group, you have to make sure the only ways the groups differ from one another was on hypersexuality. This is very difficult to do given that many studies show that those who score high on hypersexual measures tend to score high on many other measures, for example, of emotional problems.
Why did you show people pictures? Don’t most people who use porn watch sex films online?
There were many reasons to use pictures, but a major reason was to parallel previous research related to our hypotheses. This type of research, sometimes called “cue reactivity” research, studies complicated processes by breaking them down to their most basic, early responses. Like cue-reactivity research in substance addictions, the images provide a glimpse of the brain’s earliest response to a relevant (e.g., sexual) cue without allowing the person to actually act (e.g., masturbate, select the next image) on the cue as they normally might. A similar study, for instance, shows cocaine addicts pictures of cocaine without allowing them to use cocaine.
What about sex addicts who visit prostitutes or cheat?
We did not study those individuals. The overwhelming majority of people seeking treatment for sex addiction report that their only, or main, problem is their frequency of viewing sexual images.
Who funded this study?
This study was supported by a grant from the Idaho State University, Graduate Student Research and Scholarship Committee awarded to Cameron Staley, Ph.D., for his dissertation research. These grants are competitive and are awarded based on the merit of the science. He also won an award for this research from the International Academy of Sex Research.
What does this mean for those in treatment for sex addiction now?
Nothing. The study needs to be replicated. Alternative explanations need to be explored. If the wrong model is currently being used to provide treatments, we must find the right model to help people struggling with their sexual behaviors. We’re working on it!
How can I read the study myself?
The Socioaffective Neuroscience of Psychology journal is an open access journal. You can access it here.
 Lang, P. J., Bradley, M. M., & Cuthbert, B. N. (1999). The international affective picture system (IAPS): Technical manual and affective ratings.
 Franken IHA, Stam CJ, Hendriks VM, van den Brink W. Neurophysiological evidence for abnormal cognitive processing of drug cues in heroin dependence. Psychopharmacology. 2003;170: 205-12.
About the Sexual Continuum Blog
Dr. Mustanski is the Director of the IMPACT LGBT Health and Development Program at Northwestern University. You can follow the Sexual Continuum blog by becoming a fan on Facebook. He periodically live tweets from research conferences on sexuality and you can follow him@sexualcontinuum.