To the best of our knowledge, the present study is the first to specifically investigate the relationship between eating behaviors and ADHD symptoms in a sample of ADHD Egyptian children. Even though eating disorders have been demonstrated to be a significant mediating factor in the relation between ADHD and overweight/obesity in adults and adolescents, very limited evidence is available when it comes to children.
Our findings are consistent with the previous studies which have related ADHD symptoms to food approach behaviors in adults. Current literature supports that adults with ADHD show a higher prevalence of abnormal eating behaviors such as binge eating in [20,21,22]. Also, our findings are consistent with few population-based studies which support the presence of an association between disturbed eating patterns and ADHD symptoms in children [23,24,25,26].
In this study, there is a higher percentage of abnormal BMI z-scores in ADHD children more than population studies, which was also reported in other previous cross-sectional studies in children [23] and in another two cohort studies [24, 26]. However, another cross-sectional study done on non-clinical samples had found no association between ADHD and BMI in children [25]. Contrarily, two studies found that patients with ADHD who were medicated, especially methylphenidate, had lower odds of obesity compared to patients without ADHD [26, 27]. This finding was confirmed by a meta-analysis, which showed that individuals medicated for ADHD were not at higher risk of obesity, signifying that ADHD pharmacological treatment might exert a protective action on the risk of obesity development [28].
To our knowledge, only three previous studies had investigated the association between ADHD and emotional eating in children [24,25,26]. We found that ADHD positively contributed to emotional eating. ADHD children were more high emotional eaters using EES score. These results concord with results from the cross-sectional study by Tong and colleagues and the cohort study by Leventakou and colleagues [24], who concluded that there was a noteworthy positive link between emotional overeating and ADHD symptoms.
Analysis of our data showed that higher Conners global index was associated with higher BMI z-score in ADHD children. These results concord with the results from two different studies conducted on preschool children and school-aged children [29, 30]. On the other hand, another recent population-based study found no significant relation between ADHD severity and BMI z-score although it concluded that ADHD upsurge the hazard of abnormal eating in children [25]. Regarding ADHD subtypes and symptom severity and their relation to BMI, we found a positive association of severity of inattentive and, to a lesser extent, combined type with higher BMI z-scores, whereas there was a negative relation with hyperactive scores. These results agreed with results from other previous studies [30, 31], whereas other studies found no correlation between BMI z-scores and inattention or hyperactivity/impulsivity symptoms [32, 33].
The current study revealed that there was a highly significant positive association between CEBQ-food approach scores and BMI z-scores, while CEBQ-food avoiding scores were associated negatively with BMI z-scores in ADHD children. This agreed with results from most of the literature [24, 34, 35]. Moreover, a recent systematic review, conducted by Kaisari and his colleagues, concluded the same results across the life span in ADHD patients [36]. Our findings indicated that higher total Emotional Eating score was associated with higher BMI z-scores in ADHD children; moreover, high emotional eaters had a positive correlation with BMI z-scores, while low emotional eaters had a negative correlation with BMI z-scores. This agreed with the only two studies examined the relationship between emotional eating and BMI z-scores in ADHD children [24, 25]. Correlation between EES-C subscales and BMI z-scores showed that higher subscale for depression (EESC-D) and unsettlement (EESC-U) were associated with higher BMI z-scores. Contrarily, the EES-C subscale for anger/anxiety/frustration (EESC-AAF) was associated with lower BMI z-scores. This agreed with results from Tong and his colleagues who found that ADHD significantly contributed to depression, and depression directly predicted emotional overeating [25].
We used multivariate linear regression analysis for the detection of higher BMI z-scores in ADHD children. Different items assessed in this study, as emotional eating assessed by Emotional Eating Scale for Children (EES-S) total score and each subscale scores (EESC-D, EESC-U, and EESC-AAF), eating behavior assessed by Child Eating Behavior Questionnaire (CEBQ) two subscales (Food approach and food avoidant) and ADHD severity assessed by Conners global index score were analyzed. This analysis revealed that only higher emotional eating detected by higher total EES-C, not its subscales could be used to predict higher BMI z-scores in ADHD children while eating behavior and ADHD severity were not found significant in this study.
We found that ADHD children with abnormal weight (either overweight or underweight) were more than the average population of the same age. Since the risk of obesity increases in people with ADHD from childhood to adulthood, a recently published review study tried to explain their comorbidity. It found that both disorders share familial risk factors as family environment and pleiotropic genes. Besides, genes that contribute to the comorbidity of ADHD and obesity may cause deficits in executive functions, which may act as a common neuropsychological pathway of both disorders. Also, prenatal environmental factors could play a key role in the development of neuropsychological characteristics associated with ADHD, and of subsequent obesity [37].
Adjustment for other risk factors suggests that ADHD is a specific risk factor for eating pathology. Searching for the mechanism for that, a systematic review analysis found that dysfunctions in the dopamine pathways of the brain have been found among both individuals who are obese and individuals with ADHD. Besides that, individuals who have ADHD symptoms and carry genetic profiles associated with greater dopamine activation in brain reward areas are more likely to engage in overeating behaviors, such as binge and emotional eating [36].
ADHD severity was associated with higher BMI z-scores, mostly in inattentive type and to a lesser extent with combined type, while hyperactive type was associated with less BMI z-scores. Deficient inhibitory control could reinforce abnormal eating behaviors that, in turn, would increase the likelihood of obesity. Inattention and poor planning might cause difficulties in adhering to regular eating patterns and dietary regimens; additionally, a lack of attention may be associated with a lack of awareness of food intake [38]. Another important factor is the hyperactive physical component of ADHD, as motor overactivity, that would intuitively be considered to decrease, rather than increase, the risk of obesity; assuming that it increases energy expenditure and weight loss. A previous study had showed that ADHD (predominantly inattentive type) children were 57% less likely to meet recommended levels of physical activity than controls [39].
ADHD children showed a positive association between CEBQ food-approach behaviors and BMI z-score, while CEBQ food-avoidant behaviors were associated negatively. Also, correlation of EES-C score and BMI z-scores in ADHD children revealed that there was a positive correlation between BMI z and EES-C total scores, as most of ADHD children with high EES have higher BMI-z, and vice versa.
Regarding ADHD types and their relation with EES-C, there were higher EES-C scores among both inattentive and combined types, but not among the hyperactive type. A speculated mechanism to explain this association is that children with ADHD may face more stress and negative emotions which increase the risk of emotional eating behaviors as a maladaptive coping mechanism as individuals involve in emotional eating mostly when they are experiencing difficulty in coping with negative emotions. Emotional eating is associated with a range of psychological problems, such as low self-esteem and feelings of inadequacy, social anxiety, and mood disorders. Children with ADHD often suffer from low social recognition, problematic peer relationship, poor academic achievement, and high concurrence with mood disorders, which may contribute to emotional eating [25]. There are many limitations to our study, as it was limited by the sample size; thus, caution should be exercised in the generalization of the results of this study, and more research should be carried out on larger samples to replicate these results. Another limitation of our study was that it was cross-sectional in nature, and although it helped identify associations, it was difficult to infer causality in relationships. A longitudinal study would help answer many questions in this area.