Is the Relationship Between ADHD Symptoms and Binge Eating Mediated by Impulsivity?

Abstract

Objective: Individuals with ADHD may be at risk of developing binge eating disorder (BED). Impulsivity correlates with both BED and ADHD; however, more research is needed to explore whether impulsivity plays an underlying role in the observed relationship between ADHD and BED. Method: Questionnaires were used to assess ADHD and BED symptoms. Multiple questionnaires and a behavioral task were used to assess impulsivity in undiagnosed undergraduate participants (n = 50). Results: Expected correlations were found among ADHD symptoms, BED tendencies, and measures of impulsivity with the exception of impulsivity on the behavioral task and BED symptoms; however, none of the measures of impulsivity were found to be significant mediators between ADHD and BED symptoms. Conclusion: Although impulsivity may play an important role in the interrelationship of ADHD and binge eating, other factors may also be critical in the development of this comorbidity. Investigation of this research question in clinical samples is needed.

Keywords

binge eating disorder ADHD impulsivity

Binge eating disorder (BED) is characterized by excessive caloric consumption to the point of physical discomfort, and a lack of control over the consumption (Kupfer & Regier, 2013). For this reason, individuals with binge eating tendencies typically exhibit both the psychological consequences of low self-esteem and depression as well as the physiological consequences of obesity, heart disease, and diabetes (de Zwaan, 2001). Previously, BED was included in the Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV; American Psychiatric Association, 1994) as a subcategory of eating disorder−not otherwise specified (ED-NOS; de Zwaan, 2001); however, the disorder is now included as a third main category of eating disorder in DSM-5 (Kupfer & Regier, 2013).

A variety of psychological constructs have been proposed as factors related to binge eating tendencies (de Zwaan, 2001). Constructs that have been well studied include body dissatisfaction (Jackson, Grilo, & Masheb, 2000) and depression (Linde et al., 2004). However, other proposed constructs have not been tested as thoroughly. For instance, impulsivity may play a crucial role in binge eating, although this relationship is not fully understood. Past research has conceptualized impulsivity as action or behavior that is executed without appropriate forethought, inappropriate for the situation, or immoderately risky (Evenden, 1999). Impulsivity can be a part of typical everyday life, but can also take a pathological form and interfere with functioning (see Moeller, Barratt, Dougherty, Schmitz, & Swann, 2001, for a review). Impulsivity has been proposed as a contributing factor for BED as binge eating may be related to difficulties inhibiting strong urges (Nasser, Gluck, & Geliebter, 2004).

In a small preliminary study, Nasser et al. (2004) found that high levels of impulsivity correlated with BED by use of the laboratory test meal paradigm. In this study, participants were given a Boost drink to consume, and the amount of consumption was measured to examine eating-related impulsivity. Participants with BED scored higher on a questionnaire measure of impulsivity and were more likely to display behaviors consistent with the clinical criteria of BED (Nasser et al., 2004). While this study concluded that impulsivity relates to binge eating, further research is still necessary to better understand this relationship.

ADHD has been found to be comorbid with eating pathology and BED specifically at rates suggesting shared risk factors (Cortese, Bernardina, & Mouren, 2007). Previous research has examined the relationship between ADHD and different eating disorders. Biederman et al. (2007) found that adolescent girls with ADHD have a significantly higher risk of developing bulimia nervosa, an eating disorder correlated with impulsivity, than other eating disorders (Biederman et al., 2007). In addition, in a longitudinal study, Mikami, Hinshaw, Patterson, and Lee (2008) found that impulsivity best predicted eating pathology in girls with ADHD. Also, other research has found that women with bulimia nervosa are more likely to also experience ADHD symptoms than controls, and that these women showed more impulsivity than individuals with only bulimia and experienced even greater disordered eating (Seitz et al., 2013). In females, ADHD predicted impulsivity-related bingeing and purging eating behavior, and did not predict control-related restrictive behavior (Bleck & DeBate, 2013). The present study aims to empirically examine the role of impulsivity in the ADHD–binge eating relationship.

As ADHD is potentially comorbid with eating disorders, and presence of ADHD could exacerbate eating pathology and make treatment of these disorders even more difficult, fully understanding this relationship is highly important (Cortese et al., 2007). The purpose of the present study was to examine the extent to which impulsivity could account for the relationship between ADHD symptoms and binge eating tendencies in a non-clinical sample. As ADHD symptoms have a dimensional structure in the population (Marcus & Barry, 2011), we focused this initial investigation on examining the relationships among these constructs in an undiagnosed sample. Importantly, impulsivity was measured using multiple methods including three questionnaire measures and a laboratory task and we used bootstrap analyses to test the indirect effect of ADHD symptoms on binge eating via impulsivity (Hayes, 2013). We hypothesized that impulsivity would be a significant mediator of the ADHD–binge eating relationship.

Methods

Participants

Fifty undergraduate students were recruited from a small, private liberal arts university in the Mid-Atlantic Region. Participants ranged in age from 18 to 22 (M = 19.2) and varied in self-reported race and ethnicity: Caucasian, 65.3%, Asian and Asian American, 20.4%, African American, 10.2%, and Hispanic, 4.1% of the sample. Participants were mostly female (n = 36) and the majority of participants fell into the normal classification of body mass index (BMI) with BMI ranging from 17.0 to 33.9 (M = 22.4).

Measures

Descriptive statistics and internal consistency (Cronbach’s α) appear in Table 1.

Table 1.

Descriptive Statistics and Correlations Between ADHD Symptoms, Binge Eating Symptoms, and Measures of Impulsivity.

Measure	1	2	3	4	5	n	M	SD
1. Binge Eating Scale	α = .89					50	11.4	7.03
2. BAARS-IV ADHD symptoms	.37**	α = .86				50	31.7	7.7
2. BAARS-IV ADHD symptoms	.009
3. Barratt impulsiveness	.26	.66**	α = .79			50	48.2	11.4
3. Barratt impulsiveness	.067	<.001
4. Impulsiveness questionnaire	.25	.40**	.48**	α = .63		50	12.6	3.4
4. Impulsiveness questionnaire	.086	.004	<.001
5. BDEFS	.26	.67**	.52**	.33*	α = .87	50	35.5	8.46
5. BDEFS	.066	<.001	<.001	.020
6. Go/No-Go commission	−.02	.38*	.24	.30	.27	39	34.8	21.2
6. Go/No-Go commission	.914	.018	.142	.065	.095

Note. Correlations are Pearson correlations (r) with significance values beneath. Values on the diagonal are Cronbach’s α (internal consistency). BAARS = Barkley Adult ADHD Rating Scale; BDEFS = Barkley Deficits in Executive Functioning, Self-Restraint.

p < .05. **p < .01.

Impulsivity

Because varying theoretical models of impulsivity have been proposed and because of the potential utility of examining impulsivity using multiple methods (Moeller et al., 2001), we measured impulsivity using three different questionnaires and a behavioral task.

Barratt Impulsiveness Scale (BIS-11)

This questionnaire is a widely used measure of self-reported impulsive personality traits (Patton, Stanford, & Barratt, 1995). It is comprised of 30 items that yield six first-order and three second-order impulsiveness factors. We used the total score as opposed to scores on the individual subscales because this had the strongest correlation with ADHD symptoms. Participants rated their agreement with a series of statements on a 7-point Likert-type scale. An example item is “I act without thinking.”

Impulsiveness Questionnaire (I₇)

This self-report questionnaire also assessed impulsiveness, but focused on emotional aspects of impulsivity to a greater extent than the BIS-11 (Eysenck, Pearson, Easting, & Allsopp, 1985). We used the 25-item version of this questionnaire; each item required a response of “yes” or “no” as to whether participants agreed with certain statements. A sample statement is “I buy things impulsively.”

Barkley Deficits in Executive Functioning, Self-Restraint subscale (BDEFS)

The BDEFS (Barkley, 2011b) assesses self-reported deficits in executive function in daily life. The four-item Self-Restraint subscale from the BDEFS was used for the present study. Participants were asked to convey the frequency of self-restraint problems experienced in the past 6 months on a 4-point Likert-type scale. An example item is “Unable to inhibit my reactions or responses to events.”

Letters Go/No-Go task

This computerized continuous performance task, programmed in Eprime 1.0 and downloaded from a website providing free computerized tasks for research (www.sacklerinstitute.org/cornell/assays_and_tools), is a behavioral measure of impulsivity (Casey et al., 2007). Participants responded to repeated presentations of a visual stimulus (all letters except “X”) by pressing the space bar, and inhibited response following a distinctive, infrequent stimulus (letter “X”). The proportion of commission errors was used to index impulsivity.

Binge eating tendencies

We used the Binge Eating Scale (BES; Gormally, Black, Daston, & Rardin, 1982) to measure self-reported binge eating behaviors and cognitive and emotional responses to those behaviors associated with the BED category of ED-NOS in DSM-IV. The questionnaire presented grouped statements of three to four items. Each group contains statements that assess different levels of one aspect of binge eating tendencies. Participants indicated which statement in each group they most identified with.

ADHD symptoms

Participants completed the Barkley Adult ADHD Rating Scale (BAARS-IV; Barkley, 2011a), which assesses symptoms of ADHD over the past 6 months. Participants reported the frequency of each DSM-IV symptom on a 4-point Likert-type scale.

Procedure

All procedures were reviewed and approved by the Institutional Review Board (IRB) at the University of Richmond. Participants were recruited through a campus-wide email event notification system. Participants completed informed consent procedures and signed the IRB-approved consent form. Then, participants completed the study questionnaires via Qualtrics web-based survey software. Following the questionnaires, the participants completed the Letters Go/No-Go task on a desktop computer. The procedure lasted between 45 and 60 min, and participants were debriefed and compensated US$10.00 for their participation.

Results

Plan of Analysis

Descriptive statistics and correlations among all measures are reported in Table 1. Distribution of each measure was examined to assess whether it was suitable for parametric analysis and bivariate correlations were used to determine whether it was reasonable to conduct mediation analysis. Given significant correlations of ADHD symptoms with impulsivity measures and BED symptoms and marginally significant correlation between binge eating symptoms and impulsivity, we conducted bootstrap mediation analyses using the modeling tool PROCESS for SPSS (Hayes, 2013). This tool creates bias-corrected confidence intervals for the indirect effect of an independent variable on a dependent variable via a proposed mediator using bootstrap analysis. The statistical test for this method of mediation analysis is whether the 95% confidence interval around the estimate of the indirect effects include zero. Four simple mediation models were tested with ADHD symptoms as the predictor, binge eating tendencies as the dependent variable, and each of the four measures of impulsivity as the proposed mediator. Models were tested separately for men and women to determine whether any effects were dependent on gender. Results did not differ by gender and so results for all participants combined are reported.

Correlations

Out of 50 participants, 44 had complete data available for all measures. Six participants were unable to complete the Go/No-Go task due to technical difficulties. Go/No-Go data from an additional five participants had questionable validity because omission error scores were outliers (omission error cutoff of 34 or more). When we conducted analyses using the Go/No-Go task with these five participants included versus excluded, the results did not change; however, we present the analyses excluding participants with questionable validity. Bivariate correlations (Table 1) revealed that ADHD symptoms were significantly correlated with binge eating symptoms and with measures of impulsivity (e.g., BIS: r = .66, p < .001). Correlations between binge eating symptoms and self-reported impulsivity approached significance (e.g., BIS: r = .26, p = .067). Binge eating symptoms did not correlate significantly with Go/No-Go commission errors.

Mediation Analyses

Mediator: BIS

With impulsivity as measured by the BIS in the model as a mediator (see Figure 1, top panel), the direct effect of ADHD symptoms on binge eating tendencies was marginally significant (B = .31, p = .065). Although ADHD symptoms predicted BIS impulsivity (B = .98, p < .001), BIS was not significantly associated with binge eating (B = .02, p = .849) when controlling for the effect of ADHD symptoms. A bias-corrected confidence interval for the indirect effect (.02) based on 10,000 bootstrap samples included zero (−.248 to .294), indicating that impulsivity as measured by the BIS was not a mediator of the relationship between ADHD symptoms and binge eating tendencies.

Figure 1.

Top Panel: Impulsivity as measured by the Barratt Impulsivity Scale as a mediator of the relationship between ADHD symptoms and BED symptoms. Bottom Panel: Impulsivity as measured by percent commission errors on the Letters Go/No-Go task as a mediator of the relationship between ADHD symptoms and BED symptoms.

Mediator: I₇

With impulsivity as measured by the I₇ Impulsivity Questionnaire in the model as a mediator, the direct effect of ADHD symptoms on binge eating tendencies was significant (B = .29, p = .04). Although ADHD symptoms predicted I₇ impulsivity (B = .18, p = .004), I₇ was not significantly associated with binge eating (B = .24, p = .427) when controlling for the effect of ADHD symptoms. A bias-corrected bootstrap confidence interval for the indirect effect (.04) based on 10,000 bootstrap samples included zero (−.084 to .180), indicating that impulsivity as measured by the I₇ was not a mediator of the relationship between ADHD symptoms and binge eating tendencies.

Mediator: BDEFS

With impulsivity as measured by the BDEFS in the model as a mediator, the direct effect of ADHD symptoms on binge eating tendencies was marginally significant (B = .31, p = .067). Although ADHD symptoms predicted BDEFS (B = .19, p < .001), BDEFS was not significantly associated with binge eating (B = .11, p = .851) when controlling for ADHD symptoms. A bias-corrected bootstrap confidence interval for the indirect effect (.02) based on 10,000 bootstrap samples included zero (−.196 to .227), indicating that impulsivity as measured by the BDEFS was not a mediator of the relationship between ADHD symptoms and binge eating tendencies.

Mediator: Go/No-Go commission errors

With impulsivity as measured by Go/No-Go percent commission errors in the model as a mediator (see Figure 1, bottom panel), the direct effect of ADHD symptoms on binge eating tendencies was significant (B = .38, p = .017). Although ADHD symptoms predicted Go/No-Go commission errors (B = .009, p = .018), Go/No-Go percent commission errors were not significantly associated with binge eating (B = −6.83, p = .302) when controlling for the effect of ADHD symptoms. A bias-corrected bootstrap confidence interval for the indirect effect (−.06) based on 10,000 bootstrap samples included zero (−.251 to .032), indicating that impulsivity as measured by Go/No-Go commission errors was not a mediator of the relationship between ADHD symptoms and binge eating tendencies.

Discussion

Although ADHD symptoms were positively correlated with binge eating tendencies and all measures of impulsivity, none of the measures of impulsivity we tested was a significant mediator between ADHD and binge eating symptoms. Using a powerful method of testing mediation—bootstrap analysis of the indirect effect—and multiple measures of impulsivity, the observed relationship between ADHD and BEDs symptoms in this sample could not be explained by impulsivity. Although the correlation between ADHD symptoms and binge eating symptoms we obtained in our sample is consistent with past evidence that individuals with ADHD may be more likely to develop impulsivity-related eating disorders than control-related eating disorders (Bleck & DeBate, 2013; Mikami et al., 2008), it indicates that impulsivity alone may not entirely explain the connection between these two disorders.

Thus, other factors in addition to impulsivity may account for the observed relationship between ADHD and BED. Previous research has suggested that ADHD may be linked to anxiety, depression, and emotion regulation problems (Casey et al., 2007). While BED is still an emerging area of research, preliminary studies have found that binge eating is also related to these constructs (Jackson et al., 2000). Thus, future studies could investigate whether anxiety, depression, or emotion regulation mediates the relationship between ADHD and BED. For example, emotion regulation correlates with ADHD and may also relate to BED as binge eating tendencies may provide a sense of comfort or alleviation of distress, and a learned pattern may develop between emotional distress and binge eating. Future research could study clinical populations; compare participants in different age, BMI, or demographic ranges; and, perhaps most importantly, study other potential mediators such as internalizing disorders or emotion regulation.

This study is a preliminary investigation into the role of impulsivity in explaining the relationship between ADHD and binge eating and has several limitations. The main limitation is that our sample was non-clinical. Although we used self-report measures that have been used with non-clinical populations in past studies and found a reasonable amount of variance on these scales, we did not study individuals with clinical diagnoses. While we assessed impulsivity using multiple methods, ADHD and binge eating symptoms were only assessed using self-report. Future research should be conducted using a clinical sample. In addition, a study in a more diverse non-clinical sample would also be important in seeking to replicate our results. Also, different age groups should be compared to find the critical period for individuals managing both disorders such that optimal intervention programs can be designed based on age.

Understanding the relationship between ADHD and BED is important for people struggling with both disorders. Previous research has demonstrated that there may be correlation between ADHD and BED (Cortese et al., 2007; Mikami et al., 2008), and the present study provides support for this finding. While the present study also provides evidence that ADHD symptoms and binge eating symptoms are positively correlated with impulsivity (Casey et al., 2007; Nasser et al., 2004), the present study did not find that impulsivity was a significant mediator of the relationship between ADHD and BED, suggesting that other factors may be important to understanding this relationship. Future research about mechanisms underlying the observed relationship between ADHD and BED will help build the most effective possible interventions and may inform strategies for children with ADHD to prevent binge eating patterns before they form.

Footnotes

Acknowledgements

Our sincere thanks to Leah Doghramji and Caroline Smith for their assistance with data collection on this project.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This research was supported by an undergraduate research grant from the School of Arts and Sciences at the University of Richmond awarded to the first author.

Author Biographies

Kylie M. Steadman recently graduated magna cum laude from the University of Richmond with a Bachelor of Science degree in Psychology. The present study is based on her research for her senior honors thesis. Her primary research interests include binge eating disorder and its related factors, and dieting and motivation.

Laura E. Knouse is an Assistant Professor of Psychology at the University of Richmond. She received her PhD from the University of North Carolina at Greensboro and completed her post-doctoral fellowship at Massachusetts General Hospital and Harvard Medical School. Her research interests include many aspects of ADHD in adults including cognition and metacognition, the development of comorbidity, and cognitive-behavioral treatment approaches.

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