RIESGOS DE SEGUROS

The direct comparison of obesity with addictive behaviour offers an awkward analogy;

in favour of this comparisson, both eating and consumption of elicit drugs are

associated with pleasure (Greeno, Wing, & Shiffman, 2000). However, the consumption of drugs (such as cigarettes, narcotics or alcohol) does not enhance or contribute to survival, whereas eating is not really optional. Moreover, since the choice to overeat includes components from the central nervous system, physiological inputs, in addition to psychological motivational components (Lowe, 2009) it could be argued that

overeating is a considerably more complicated dilemma. Notwithstanding, behavioural aspects of overeating pleasant tasting food do show some remarkable similarities with overconsumption of drugs of abuse. Consider that despite extremely costly investment into weight loss programs (estimated at $40 U.S. billion per year (Reisner, 2008 http://www.businessweek.com/debateroom/archives/2008/01/the_diet_indust.html ) coupled with the fact that 85% of those individuals who try to lose weight gain it back within two years.

Most importantly, if overeating was such an easy habit to extinguish, it is likely the obesity crisis would not exist. Critically, impulsivity has a pivotal role in most forms of appetitive addictive behaviour. Since appetitive addiction includes a range of

behaviours (including consumption of elicit drugs, smoking, and recently binge eating (Pelchat, 2009), examples will be taken from each of these fields to demonstrate the critical role impulsivity has in differentiating addiction prone versus resistant individuals.

Recent investigations have found impulsiveness underlies both the initial

experimentation with drugs (Carroll, Anker, & Perry, 2009; Perry & Carroll, 2008), the inability to stop substance abuse (Belin, et al., 2008), and critically that certain subtypes

of impulsivity more suited to discriminate animals‟ risk for developing compulsive habits with regard to the consumption of drugs (Crews, 2009). Since habitual

overconsumption of food is likely the most difficult behaviour to change in the case of obesity (C. Davis, Carter, J.C., 2009; C. Davis, et al., 2004; S. S. Davis C., Berkson M., 2004; Pelchat, 2009), isolating the subtype of impulsivity most reliably associated with overeating would enhance our understanding of the individual risk factors positively associated with the development of obesity.

The concept of “willpower” is a critical area of addiction based psychological

investigations. Mischel (1974) originally investigated delay of gratification tasks, and how a 4-year old child‟s ability to control the urge to eat one marshmallow in the laboratory in preference for 2 marshmallows after a 15 minute time delay, could relate to better long term planning and goal achievement later in life. Mischel began his original investigation into delay-of-gratification tests with a group of preschool children and subsequent longitudinal demonstrated that 4-year olds who were able to withstand temptation for eating the 1 marshmallow were also more attention, had better

concentration, exhibit greater self control, and also score higher on the SAT and perceived as more interpersonally competent by parents and peers (Mischel, Shoda, &

Rodriguez, 1989). Data also confirmed that children who waited for 2 marshmallows were less likely to subsequently use drugs (Ayduk, 2000).

Impulsive choice, or inability to perform in delay-of-gratification tasks would fit within Evenden‟s definition of Reward Reactive Impulsivity, and is also associated with abuse of cigarettes (S. H. Mitchell, 2004), marijuana (Kollins, 2003), alcohol (J. M. Mitchell, Fields, D'Esposito, & Boettiger, 2005), and cocaine (Coffey, Gudleski, Saladin, &

Brady, 2003). It has been shown that adolescents who were more impulsive (defined as a pervasive choice for Small Soon versus Large Later rewards) were less likely to achieve abstinence from a smoking cessation program compared to adolescents who were less impulsive (Krishnan-Sarin, et al., 2007). In terms of eating behaviour literature, obese women are also significantly more impulsive on tasks that assess preference for Small Soon versus Large Later rewards (Weller, et al., 2008)and what is most directly relevant to the theme of this thesis, is that lean women who self report high TFEQ-D scores are also significantly more impulsive on a measure of delay

discounting than those with low TFEQ-D scores (M. R. Yeomans, Leitch, & Mobini, 2008).

A relatively new tool to investigate Reward Reactivity, is the Balloon Analogue Risk Task (C. W. Lejuez, et al., 2002). This is a laboratory performance measure of

impulsivity that simulates real-life risk taking situations as participants are rewarded by their election to continue clicking on a balloon (each click represents a theoretical monetary value), or save the money they have accrued. The larger the balloon, the more money it is theoretically worth but so too is the possibility that all money will be lost with one explosion thus jeopardizing the participants greater goal of gaining as much money as possible. Participants do not have any knowledge or strategy to win money on this game, as the task is set to a Variable Ratio schedule, with balloons popping at random. As with real life situations, risk is rewarded until a certain point. When one balloon explodes, the participant is presented with another opportunity to pump up the next balloon, until the task is finished.

Greater explosions on the BART have been associated with self-report and real world measures of riskiness; for example, ever-smoking adolescents (those who have smoked even one puff) compared to never smoking adolescents were significantly more

impulsive and reported significantly higher sensation seeking scores (C. W. Lejuez, et al., 2002). Performance on the BART has been reported with self-reported addictive, health and safety risk behaviours in young adults and adolescence beyond those that would be accounted for demographics (C. W. Lejuez, et al., 2003; C. W. Lejuez, et al., 2002).

A key question then is whether the BART measures Reward Reactivity or Response Inhibition in relation to Evendon‟s classification. Although there are arguments that both elements of impulsivity could contribute to poor performance on this task, overall is seems likely that the BART will be more sensitive to Inhibition Impulsivity, as Balloon Explosions are a product of a participants‟ inability to stop inflating the balloon, rather than a myopia for future outcomes in the form of preference for Small rewards Soon in contrast to Large rewards Later. In this way, the BART does not fit within the parameters of impulsivity prescribed by the terms of Reward Reactivity; an adaptive strategy on this task would be to pump the balloon as much as possible, thus if

a participant ascribes to a “Large Later” type of rationale, they will be deemed as impulsive (by virtue accruing more balloon explosions). As such, those participants who are able to control their clicks to the balloon with pauses and consideration for the size of the balloon in relation to likelihood for its explosion, are more likely to succeed in this task. As such, the ability to control responding is the key variable in this task, which would mean it is a task of Inhibition impulsivity.

The simple distinction of Reward Reactive versus Inhibition subtypes of impulsivity has significant bearing determining animals that are at risk for habitual compulsive

consumption of drugs to those who merely experiment but do not develop a life threatening addiction. For example, recent findings have demonstrated that impulsive animals, who fit within Evenden‟s classification of Inhibition subtype as opposed to Reward Reactive, are more vulnerable to habitual consumption of drugs (Belin, 2009).

The finding that animals that could be categorized into a specific province of impulsive behaviour, Inhibition Impulsivity, and also had a significantly greater propensity for developing an addiction to cocaine demonstrates the utility of refining the hypothesis that “impulsivity” is generally associated with addictive behaviour. The following section is devoted to several animal studies which also demonstrate the value of classifying the impulsivity construct.