Attention deficit hyperactivity disorder (ADHD), characterized by inattention, hyperactivity, and impulsivity, is a common childhood disorder. ADHD can often persist into adolescence and adulthood. The prevalence of ADHD is thought to be between 6-7% among children and adolescents and ~5% among adults (Willcutt, 2012).
Increasingly, evidence from multiple studies has pointed to comorbidity between ADHD and eating disorders (EDs). For example, one study found that young females with ADHD were 5.6 times more likely to develop clinical (i.e., diagnosable according to DSM-5) or subthreshold (i.e., sub-clinical) bulimia nervosa (BN) (Biederman et al., 2007). Another study found that found that 21% of female inpatients at an ED unit had six or more ADHD symptoms (Yates et al., 2009).
However, most previous studies are limited by the fact that they assessed comorbidity between ADHD and EDs among patients. This limits our ability to generalize these findings to community samples, where many may experience symptoms of the disorders at subthreshold levels. Moreover, most studies focused on bingeing/purging behaviours and did not investigate differences between ADHD subtypes.
In the current study, Jennifer Bleck and colleagues sought to expand upon a previous study (published in 2013) and address the following questions:
- Do clinical/subclinical ADHD and clinical/subclinical EDs co-occur in a nationally representative sample?
- Does the relationship differ by type of disordered eating behavior and or ADHD subtype?
Using data from the National Longitudinal Study of Adolescent Health, Bleck et al. analysed data from 12,262 participants (51% females). EDs were assessed when participants ranged from 18 to 27 years (average age was 21.8 years). The majority of participants were Caucasian (67%), 15% were African-American, 11% were Hispanic, and 4% were Asian.
SUMMARY OF MAIN RESULTS
- 5.5% reported having been told by a health care provider that they had ADHD
- 2.1% reported having been told that they have an ED
Among those who were not told they had an ED or ADHD (i.e., excluding the above 827 participants):
- 3.9% reported inattentive ADHD behaviours
- 8.5% reported hyperactive/impulsive ADHD behaviours
- 7.1% reported bingeing and/or purging behaviours
- 14.3% reported restricting behaviours
WHAT ABOUT COMORBIDITY BETWEEN ADHD and EDs?
Bleck and colleagues found that 4.2% of those who reported clinical ADHD also reported clinical EDs, compared to 2.0% of those without ADHD. Overall, those with clinically diagnosed ADHD were ~4 times more likely to engage in clinical-level restrictive and bingeing and/or purging behaviours.
Among those who reported ADHD behaviours but were not diagnosed with ADHD, between 10.6-11.7% also reported subthreshold bingeing and/or purging behaviours, compared to ~6-7% among those without ADHD symptoms. Conversely, there were no differences in subthreshold restrictive eating behaviours between those with subthreshold ADHD and those without. There were no differences between inattentive and hyperactive/impulsive ADHD subtypes.
The image below summarizes the main findings:
Findings from the current study suggest that those with clinical ADHD are more likely to experience (a) clinical EDs, (b) clinical-level binge and/or purge eating behaviors, and (c) clinical- level restrictive eating behaviors. On the other hand, those with subclinical ADHD are more likely to experience subclinical binge and/or purge eating behaviors while there was no evidence to suggest a relationship between subclinical ADHD and subclinical restrictive behavior.
WHAT DO THESE FINDINGS MEAN?
Since this was a cross-sectional study, we can’t make any conclusions about the nature of the relationship between ADHD and EDs. Thus far, we just know that there’s an association. There are, however, theories about how the two may be linked:
One theory states that the poor planning and difficulty monitoring one’s behavior manifestations of ADHD may lead to overeating, while another states that ADHD patients may be inattentive to internal signs of hunger and forget to eat when engaging in interesting activities leading to binge eating when less stimulated. An alternative explanation suggests that binge eating is a compensatory mechanism to help control the frustration associated with attention and organizational difficulties.
Not knowing much about ADHD, it is difficult for me to assess how plausible those theories sound. Although, to me, they sound a bit too simplistic. Importantly, the aforementioned theories are not mutually exclusive — it could very well be that all three (or more!) possible causes lead to disordered eating behaviours among individuals with ADHD.
As always, the results must be interpreted with the study’s limitations in mind. Here are the main two:
- All disordered eating behaviours were self-reported and retrospective. Moreover, participants were asked to report on disordered eating behaviours within the previous week only, likely undercounting the amount of individuals engaging in those behaviours.
- An individual was categorized as having clinical-level ADHD if he/she reported being told by a health professional that he/she had ADHD, but the questionnaire did not assess who made the diagnosis and how the diagnosis was made (i.e., was it made using appropriate procedures). (A similar issue is true for the way individuals with clinical-level EDs were categorized as well).
TAKE-HOME MESSAGE FOR CLINICIANS & PARENTS
As findings from this paper suggest, a substantial portion of individuals with clinical-level and subthreshold ADHD exhibit disordered eating behaviours. Consequently, clinicians and parents should be aware of the increased prevalence of clinical and sub-clinical eating disorders among individuals with ADHD, especially bingeing and/or purging, and be particularly vigilant about assessing and/or monitoring children and adolescents diagnosed with ADHD for disordered eating behaviours.
For those of you with ADHD and EDs, what do you think of the findings and what do you think may be behind the association between ADHD and EDs? How do you feel your ADHD and ED relate and/or interact, if at all?
Bleck, J., DeBate, R., & Olivardia, R. (2014). The Comorbidity of ADHD and Eating Disorders in a Nationally Representative Sample The Journal of Behavioral Health Services & Research DOI: 10.1007/s11414-014-9422-y