There is a marshmallow in front of you. Can you wait for twenty minutes, starring intently at the white, soft, cylindrical shaped sweet, to get another marshmallow? Or do you devour it right away, forgoing the opportunity to have two sweets?
I’d probably wait. But that’s only because I don’t like marshmallows, and would be in no rush to consume either one or two of them. What about you?
That’s the famous experiment that’s shown to many first year psychology undergrads (I, too, watched videos of little kids anxious waiting for 20 minutes, or not, in my first year psych class). It was designed to measure delayed gratification, in other words, are you able to wait, to get a reward, to delay gratification?
Leah recently asked whether studies have looked at delayed gratification in eating disorder patients. What I loved about her comment is that she included a hypothesis: “I would imagine sufferers of AN and BN would gravitate towards delayed gratification because of the mindset suffer now to be thin later. I think the opposite would hold true for BED, where sufferers binge to fill a present “emptiness,” instantly gratifying desires, while ignoring aftermath.”
So, I checked it out. I choose to search for impulsivity/impulse control instead of delayed gratification as it is a more ubiquitous term that encompasses the concept of delayed gratification. I stumble upon Samantha Waxman’s 2009 review of 12 studies on impulsivity in eating disorders. The best way to learn about a new topic is to read recent reviews: it gives you the whole picture, a nice overview of where the subfield is, what the current problems and limitations are and what questions remain.
Impulsivity is “a multidimensional concept that involves ‘an impulse, the behavioural expression of that impulse, and the situation in which both occur'”. Impulsive behaviours are “spur of the moment”, there’s no pause to consider the long-term consequences for oneself or for others. It is difficult to study such complex concepts because the result may very well depend on the way one defines “impulsive” and how one chooses to assess or screen for that trait (keep that in mind).
Dawe and Loxton (2004) identified two independent factors of impulsivity:
- reward sensitivity/discounting: inability to delay reward, “increased tendency to choose immediate small rewards over larger delayed ones” (in other words, not waiting 20 minutes to receive a second marshmallow and eating the first right away)
- rapid response/rash spontaneous impulsivity: “responding without adequate assessment of context”
What do we know about EDs and impulsivity?
Waxman provides an introduction and overview to the field:
- Impulsivity is associated with bingeing behaviours (in bulimia nervosa (BN) and anorexia nervosa – binge/purge subtype (ANBP/ANP in this paper)
- Bingeing/purging behaviours have also been associate with “self-injury, stealing, sexual promiscuity and substance abuse”
- Increased impulsivity was correlated with severity of the ED, decreased psychological functioning and Cluster B personality disorders
- Impulsive behaviours in ED patients were also associated with “distorted biochemical functioning, less effective coping strategies and poor treatment outcomes and long-term prognosis
- MIB = multi-impulsive bulimia: bulimia nervosa with the presence of at least three other typically impulsive behaviours (substance abuse, suicide attempts, self-injury, stealing, sexual promiscuity). Some researchers suggest this is a distinct subgroup within bulimia nervosa.
Waxman surveyed the literature to find studies examining EDs and impulsivity published between 1998 and 2008. She focused exclusively on studies of adults (at least 18 years old) to avoid, as she wrote “potential confounds associated with development” (ie, rebellious teenage years). Binge eating disorder was not included because it is not currently in the DSM-IV or ICD-10. Twelve studies were included in this review.
- Only 7/12 studies had control groups, and of them, only 4 had matched controls – and even then, with the exception one, only matched by age. I get that it might be hard to find controls matched for educational level, employment, socioeconomic status, marital status, etc.. but it is so important.
- All of the studies grouped non-purging and purging bulimics into one group. However, previous work by Favaro et al. (2005) suggested that purging behaviour is actually an important predictor of the “presence and number of impulsive behaviours.. those in the non-purging bulimia nervosa group showed a lowered prevalence of impulsive behaviours”. Interesting, but makes me wonder if this is actually true in the population, or perhaps that result is due to the way in which impulsivity was measured and the specific demographic studies.
- Only females were included in the statistical analyses, so these findings may not be generalizable to the male ED population.
- 7 studies (58.3%) used ONLY self-report measures to assess impulsivity: “…it is important to acknowledge that social desirability and the possibility that participants lack insight into their current behaviours challenge the accuracy of participants’ responses. As such, much of the research on impulsivity and EDs is restricted by the inherent limitations of self-report measures.”
- Others included behavioural or physiological assessments as well (computer tasks to measure responsiveness to reward to response inhibition). A major limitation here is that these: “tasks are usually administered in a relatively neutral environment, and do not take into account factors that may affect impulsivity (e.g. autonomic arousal; Enticott et al., 2006), and thus may have limited generalizability.”
- Physiological indicator used in one study was to test the suppression of cortisol (stress hormone), but this to is highly influenced by “external and internal state variables relate to stress”
Do the self-report, behavioural and physiological measures of impulsivity correlate?
Butler and Montgomery (2005) found reduced self-reported impulsiveness and venturesomeness in participants with AN, while the results on the behavioural task.. suggested fast and inaccurate, or impulsive, responding….Claes et al. (2006) found an absence of significant correlations between self-reported and behavioural measures of impulsivity across ED subtypes. One hypothesis for this lack of association is that the behavioural measures are tapping slightly different aspects of impulsivity compared to the self-report and physiological measures, which were shown to be highly correlated or… the lack of findings may reflect the differing theoretical conceptualizations of the construct itself or instead, reflect the multidimensional nature of impulsivity…
SUMMARY OF MAIN FINDINGS:
from self-reported studies:
- Binge eating groups (ANBP and BN) are more impulsive than control groups, who are more impulsive than restricting anorexics
- ANBP and BN: motor impulsiveness, inattention, stimulus-seeking, reward responsiveness and fun-seeking than controls, less self-discipline, less deliberation compared to restricting types
- ANR: less likely to engage in risk-taking and sensation-seeking behaviours
from behavioural indicators (various computer tasks)
- no consistent differences, across studies, between ED groups and controls were identified
- findings between diagnostic groups (ANBP, ANR, BN) in behavioural tests were similar to the self-reported assessments for these ED sub-type comparisons
- only BN group (not ANBP) had non-planning tendencies (cognitive measure of impulsivity)
- binge eating groups (ANBP and BN) were “associated with behavioural forms of impulsivity (i.e. urgency)
The take-home message from that appears to be that bingeing/purging behaviour is an important predictor of, and appears to be associated with impulsive behaviours, not the ED diagnosis (AN or BN).
Note: that these general trends are seen in non-Western ED populations as well. The two Nagata studies reviewed in this paper, studied Japanese ED patients and found the same trends as other studies which focused on Caucasian populations (or didn’t state the ethnicity of the patients, which is another limitation). Assessing the prevalence of multi-impulsivity (MI) in Japanese women (60 with ANR, 62 with ANBP, 114 with BNP (BN purging type) and 66 controls), Nagata found (using self-reported measures):
- 2% of ANR, 11% of ANBP and 18% of BNP met criteria for multi-impulsivity (control group: 2%)
- there was a tendency for those individuals with multi-impulsivity to exhibit these behaviours PRIOR to ED onset, whereas those with uni-impulsivity seemed to develop an ED prior to onset of impulsive symptoms
- MI was associated with childhood parental loss
- Myers et al. (2002): patients with MI were more likely to be physically, sexually and emotionally abused as children; this could lead to “the development of affective dysregulation, inadequate control of impulse behaviours”)
presence of maternal psychiatric history was found to predict impulsive behaviours in those with an ED. This variable may suggest a genetic predisposition for developing impulsive behaviours in those with an ED *OR* it may represent the lack of an adult role model during adolescence (Favaro et al., 2005).
The differences between those with and without MIB suggest meaningful differences in etiology and pathophysiology. It also is possible that MIB results from traumatic experiences, and that bingeing and purging behaviours are used to regulate affect (Wonderlich et al., 2001).
Impulsivity does NOT emerge as a consistent risk factor for the development of an eating disorder, although few prospective longitudinal studies have been done to assess this.
Waxman puts forth two possible models that explain the relationship between impulsivity and EDs:
The first model posits that impulsivity is a predisposing causal factor in the development of EDs, specifically those with bingeing/purging behaviours, in addition to the other biological, psychological and social factors known to predispose an individual to develop an ED. The second model proposes that impulsivity acts as a moderator such that it influences the expression of ED behaviour. More specifically, various biological, psychological and social factors lead to the development of AN or BN…
Given the findings from the current review, the second model seems more appropriate. For example, individuals with AN develop either the restricting or binge/purge type. Those with ANP appear to be more similar to individuals with BN, and consistently show more impulsivity than controls and those with ANR.
These models have yet to be tested empirically.
Impulsive behaviours seem to predict poorer prognosis and treatment outcome. Thus, it is important to assess impulsivity, even simply through questionnaires, in order to provide appropriate treatment. Waxman suggests that might mean “addressing the underlying impulsivity rather than only addressing the ED behaviours”.
Secondly, and I found this to be very true in my case: “Bulimic and impulsive behaviours typically occur in response to stress, with the bingeing and/or purging alleviating the distressed feelings or negative affect.” Acute stress, discomfort, a general feeling of “not-okayness” is a huge trigger for bulimic symptoms because, I (and I know others do too) find self-induce vomiting to be very anxiolytic.
Waxman suggests that clinicians assess an individual’s ability to cope with stress, and perhaps find ways, whether through exercise, therapy or pharmacological treatments, to better able to cope with stress. For me, reducing rapid-onset acute-stress which provokes almost a gut-instinct desire to engage in engage in bulimic symptoms, has been very helpful in reducing bulimic symptoms. But of course, it took years for that behaviour to become the go-to method for alleviating certain feelings and emotions; it wasn’t always this way, not for the first few years when I exclusively fell into the anorexia-restricting type category.
… although few individuals with ANR are able to restrict their eating for prolonged periods of time, previous research has suggested that many individuals experience a breakdown of this ‘hypercontrol’ and move to ANP, followed by BN (Keel, Dorer, Franko, Jackson, & Herzog, 2005). Given this finding, Butler and Montgomery (2005) suggest that levels of self-control and impulsivity can change over time, which has important implications for treatment. For example, the authors have recommended monitoring an individual’s impulsivity over time to watch for changes in presentation. The focus of this clinical intervention would be to address self-control and impulsivity without specifically having to discuss eating behaviours.
WHAT ABOUT TREATMENT?
It appears that DBT, or dialectical behavioural therapy is one of the better approaches for managing impulsive behaviours. “DBT is a skills-based approach for teaching individuals general problem-solving skills, emotional regulation strategies and distress tolerance.” Drugs can help, too. Anti-depressants seem to be helpful in reducing bingeing and purging behaviours in some.
Ah, this post is getting long. Anyway, there’s a LOT more research that needs to be done in this area, both on the basic science side and on the clinical side. I’m interested to see future studies on this topic.
Readers, do you have any thoughts on impulsivity in EDs? Was it a pre-existing trait, stable regardless of ED symptoms or does it seem to correlate with bingeing and purging systems (like it does for me)?
Do you think it is sound advice to perhaps treat aspects of impulsiveness (distress tolerance, for example) instead of treating ED symptoms directly?
Waxman, S.E. (2009). A systematic review of impulsivity in eating disorders. European Eating Disorders Review, 17 (6), 408-25 PMID: 19548249