Cerebral Hemispheres 2



Is tanning addictive?

February 9, 2015

In Walden, his masterpiece about noncomformity and simple living, Henry David Thoreau wrote, "Every generation laughs at the old fashions, but follows religiously the new." And while Thoreau was specifically talking about society's capriciousness in embracing new styles of clothing, his quote applies just as well to our preference for one shade of skin color over another. For, while many now consider a medium-dark tan to be both healthier-looking and more attractive than pale skin, only 100 years ago a tanned complexion was shunned just like a pale one is today.

Actually, a preference for pale skin has been common throughout much of human history. One reason for this may have been that pale skin used to be an indication of affluence, as it meant that the individual who possessed it didn't have to work outdoors to earn a living. A light complexion was a sign of social status, and people went to great lengths to maintain it. Often these lengths involved applying cosmetic whitening agents that contained dangerous compounds like lead oxide. The effects of such agents could range from skin damage and hair loss to death. Yet, the desire for the pale ideal still pushed many to continue to use them.

Today, however, a tan has come to represent prosperity and the possession of ample time for leisure. It means one does not have to work so much that one cannot relax by the pool or on the beach--or perhaps more likely that one has enough expendable income to pay for regular visits to a tanning salon. But like the lead-based lightening treatments of ages past, tanning exerts a physical cost. Each year over 65,000 people throughout the world die from melanoma-related causes, and it is recognized that frequent sun exposure, a history of sunburns, and frequent use of tanning beds all increase the risk of melanoma. According to one study, ten tanning bed visits in a year nearly doubled melanoma risk in individuals over thirty and increased it almost eight times in individuals under thirty.

Yet these risks don't appear to act as a deterrent for a significant number of individuals who are willing to endure sunburns or regular visits to the tanning salon simply to achieve their goal of sustaining a medium-dark tan. Almost thirty million Americans patronize tanning salons every year, helping to make indoor tanning a $5 billion a year industry in the United States and Northern Europe--an industry that has grown five-fold since the early 1990s. Frequent tanning is especially prevalent among females, teens, and young adults, and even awareness of the risks associated with tanning doesn't seem to dissuade regular tanners from engaging in the behavior. In fact, one study found that 35% individuals who came from families with a history of malignant melanoma had still used a tanning bed in the previous year.

Applying addiction criteria to tanning

The fact that some individuals continue to tan despite the very real health risks associated with it is one reason some have come to consider tanning a potentially addictive behavior, as addiction often involves continuing to do something even when there are adverse consequences linked to it. The attempt to look at tanning in the context of addiction is representative of a generally increased openness to the idea of "behavioral addictions," or addictions that are not associated with the consumption of a particular substance (i.e. a drug). The most recent version of the Diagnostic and Statistical Manual of Mental Disorders (DSM), a comprehensive guide containing diagnostic criteria for psychiatric ailments, included Gambling Disorder in the "Substance-Related and Addictive Disorders"--the first time a behavioral addiction was included in this section. Some believe this represents a shift in how we think about addictive behavior, and that it may pave the way for the diagnosis of disorders involving internet, sex, and video gaming addictions.

To investigate tanning as a behavioral addiction, researchers have modified screening and diagnostic tools for substance abuse and dependence to make them applicable to tanning. The most sophisticated effort along these lines so far has been the development of the Structured Interview for Tanning Abuse and Dependence (SITAD). The SITAD was formulated by Hillhouse et al. (2013) and was adapted from items found in the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID) that deal with opiate abuse and dependence. The SCID is a tool used to guide practitioners in making diagnoses of psychiatric disorders based on a patient interview and DSM criteria. To be classified as tanning dependent according to the SITAD, one has to meet at least 3 criteria modified from the DSM criteria for substance dependence, which include: failed efforts to cut down on the amount of time spent tanning, spending an excessive amount of time tanning or recovering from its effects, and experiencing a form of withdrawal when unable to tan, along with several other criteria.

When testing the SITAD in a sample of 325 college students, Hillhouse et al. found 10.8% met SITAD criteria for tanning abuse and 5.4% met criteria for tanning dependence--rates that are similar to rates for substance abuse and dependence seen in national surveys of substance use. Several other measures supported the validity of the SITAD, such as the fact that those who met criteria for tanning dependence tanned ten times more frequently than those who did not. A separate series of questions about euphoric reactions to tanning also indicated that these reactions were experienced to a much greater degree in those who met criteria for tanning dependence. Also, the participants completed the SITAD at two time points that were six months apart, and the two measures displayed good test-retest reliability for tanning dependence. In other words, participants who were found to be tanning dependent on the first measurement were also likely to be found tanning dependent on the second, which suggests the SITAD is reliable over time--an important quality of a valid measurement tool.

The SITAD is still a relatively untested method for assessing tanning addiction, however. It has only been tested in one population so far (i.e. college students), and despite the favorable results mentioned above there were also some potential issues. For example, although it reliably identified cases of tanning dependence, the SITAD did not appear to be very consistent in its recognition of cases of tanning abuse between the two time points. Much more work with the tool will need to be done before we can be confident in its ability to diagnose tanning addiction. However, what the SITAD and previous attempts to identify tanning addiction in the population seem to suggest is that there are individuals who do display patterns of tanning behavior that are at least somewhat similar to those displayed during addiction to drugs.

Is there a physiological basis for tanning addiction?

Thus, it seems that there are individuals who exhibit tanning behavior that in some ways resembles addiction. But what is the mechanism that could be prompting this compulsive behavior? Addictive drugs have the ability to manipulate neurotransmission in the reward system, causing people to obsessively crave and compulsively seek substances. But exposure to ultraviolet (UV) light is not as overtly rewarding as, for example, cocaine administration. Regardless, some studies have suggested exposure to UV light in frequent tanners is reinforcing, and others have proposed a way UV light exposure could lead to rewarding effects that resemble those of addictive drugs.

When the skin is exposed to damaging (and cancer-causing) UV light for an extended period of time, a defensive mechanism is initiated to protect against UV-induced DNA damage. The mechanism involves the increased production of a precursor protein called proopiomelanocortin (POMC), which is synthesized primarily by the pituitary gland. After it is produced, POMC is cleaved to form several other proteins, one of which is alpha-melanocyte-stimulating hormone (a-MSH). a-MSH stimulates the production of melanin, a pigment molecule that helps to protect the skin by absorbing UV radiation and free radicals generated due to exposure to UV light.

POMC, however, is also the precursor for another peptide: beta-endorphin. Beta-endorphin is an endogenous opioid; its actions in the body are similar to those of opioid drugs like morphine, and it is capable of promoting natural analgesia along with a sense of well-being. Thus, it may not be surprising that a commonly cited reason for enjoying tanning is that it induces a feeling of relaxation and a positive mood.

Although the potential role of endorphins in promoting a positive mood in tanners has not been verified, there is some evidence to support it. In one double-blind study, a small group of regular tanners were given sessions in both a UV tanning bed and a non-UV tanning bed (non-UV rays would not initiate the reaction that leads to increased beta-endorphin production) on Monday and Wednesday every week for six weeks. The participants were not informed of any difference between the two beds, and on the Friday of each week they were asked to choose one of the two beds to tan in. Participants chose to tan in the UV bed 95% of the time--without any knowledge that they were choosing the only bed that provided UV exposure.

A follow-up study conducted by the same research group investigated if administering naltrexone, an opioid antagonist, before tanning would reduce the preference tanners showed for a UV tanning bed. Not only did they see a reduced preference for UV tanning beds in those who had been given naltrexone before tanning, but they also saw what seemed to be withdrawal symptoms in two out of three frequent tanners given the opioid blocker. This study, however, was done with an extremely small sample (eight frequent tanners, eight infrequent tanners--only 1/2 of each group received naltrexone) and will need to be replicated before one can be at all confident in the results. Other studies, in fact, that have tested levels of beta-endorphin in participants' blood after exposure to UV light have not found any increase from baseline levels, casting some doubt on endorphins as the mechanism underlying tanning addiction.

A recent study in rodents, however, supports the endorphin hypothesis of tanning addiction. Fell et al. (2014) exposed partially shaved mice to UV light five days a week for six weeks. After a week, the mice had elevated beta-endorphin levels in their blood. UV-exposed mice also displayed greater pain tolerance, presumably due to higher beta-endorphin levels--an effect that was abolished by pre-treatment with naloxone, an opioid antagonist. Additionally, administration of naloxone caused withdrawal effects to appear in these animals, and mice that had been exposed to UV light also displayed increased tolerance to morphine, suggesting endorphin levels had become high enough to raise tolerance to opioids in general. When Fell et al. attempted these same experiments with mice genetically engineered to be deficient in beta-endorphin production, the mice exposed to UV light did not display elevated pain thresholds, withdrawal upon naloxone administration, or increased morphine tolerance, suggesting beta-endorphin was playing a critical role in these effects in wild-type (i.e. non-genetically engineered) mice.

Is tanning addictive?

Despite the positive findings in rodents, the potential physiological basis of tanning addiction in humans remains unclear. Thus, with tanning we have a behavior that some people seem to go about in a compulsive manner, and which has a plausible--but unverified--mechanism to account for it being reinforcing. The uncertainty about the physiological mechanism underlying tanning addiction should not bear too heavily on deciding if tanning could be considered addictive, however, as the neurobiological mechanism underlying addiction to most drugs was not known before we recognized them as addictive. Regardless, there has been significant controversy surrounding the inclusion of behavioral disorders like tanning addiction in the DSM and other diagnostic manuals.

One of the arguments against considering tanning a behavioral addiction is that compulsive tanning may only be a symptom of some other underlying disorder. For example, compulsive tanners may be trying to compensate for a poor body image and may even suffer from a form of body dysmorphic disorder, which is an obsessive preoccupation with some perceived physical shortcoming (in this case skin color). However, even if compulsive tanners are doing so because of a comorbid disorder, that does not suggest their behavior cannot be classified as addictive. Many alcoholics drink to self-medicate for things like social anxiety disorder, but this doesn't suggest they shouldn't be considered alcoholics.

Another difficulty some have with designating behaviors as addictive may come from our tendency to consider drug-related addictive behavior as potentially more severe than a behavioral addiction. This is understandable, as it is hard to imagine seeing the desperation we sometimes see in severe drug addiction in a compulsive tanner. However, it seems that addictive behavior--like all other behavioral patterns--falls on a spectrum of severity. And, simply because one individual's behavior is not as extreme as another does not mean he or she is not displaying a similar pattern of behavior. The DSM seems to have acknowledged this by replacing the term "substance dependence" with the more general "substance use disorder," and by modifying the diagnosis for this disorder to allow for it to be present on a spectrum that ranges from mild to severe instead of it necessarily being either present or absent.

Similarly, the DSM has begun to dissociate addiction from substances by titling their section that deals with addiction "Substance-related and addictive disorders [emphasis added]" and including a diagnosis for non-substance related disorders. When we don't define addiction as being inextricably linked with a substance, we see that it is simply an impulsive and compulsive pattern of behavior. And it seems that almost anything--not just drugs--can be the target of compulsive behavior, depending on the individual in question. Certain people compulsively use heroin, others compulsively steal (i.e. kleptomaniacs), and others may compulsively have sex, play video games, or tan.

Thus, perhaps we need a more inclusive understanding of addiction. It seems that people can get "addicted" to almost anything; it just requires a combination of the right person and the right behavior or substance. And so maybe attempting to develop diagnostic criteria for each specific focus of addiction--like the DSM does now with alcohol use disorder, opioid use disorder, etc.--is the problem; maybe we should simply be using one general set of criteria for compulsive behavior that can be applied to anything, with no additional restrictions.

Is tanning addictive? Maybe. It really depends on the definition of addiction you are using and the susceptibility of the individual who goes tanning. Perhaps a better question is: do some people display compulsive patterns of tanning behavior that knowingly puts them at risk for serious health consequences later on in life? The answer to that question seems to be yes.

Petit, A., Karila, L., Chalmin, F., & Lejoyeux, M. (2014). Phenomenology and psychopathology of excessive indoor tanning International Journal of Dermatology, 53 (6), 664-672 DOI: 10.1111/ijd.12336


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