The current study assessed the ADHD symptoms level in ED patients and ascertained differences among ED subtypes. Moreover, we evaluated the association among the severity of ADHD symptoms and eating disorder symptomatology, general psychopathology and personality.
ADHD symptoms level in ED subtypes
Our findings support the hypothesis that the ADHD symptoms level in ED patients differs between subtypes. In accordance with previous studies [14, 15], our results showed a high frequency of ADHD symptomatology in ED patients. In line with other authors [4, 11, 32], our findings showed that the more impulsive groups (namely BN, BED and EDNOS subtypes) presented a higher ADHD symptoms level compared to the AN group. The underlying reduced impulse control, a common characteristic of bingeing ED subtypes, might be a shared characteristic with the ADHD population . Accordingly, Pagoto et al.  found that poor inhibitory control, associated with deficits in executive functions, may be the main cause of overconsumption, eating without hunger and binge eating patterns. Another possible explanation for this high comorbidity between bulimic disorders (BD) and ADHD is that both disorders share common genetic risk factors. Several polymorphisms of genes and neurotrophic factors have been associated with BN  and with ADHD across life span . In the same line, genetic variants of the serotonergic system have been found to be related with BD and ADHD [36–38]. Finally, cognitive features such as rigidity and perfectionism observed in AN patients [8, 39] might explain the lower prevalence of ADHD symptoms in this sample. According to this hypothesis clinical reports document perseverative and rigid thinking styles in patients with AN [40, 41].
Association between ADHD, ED and general psychopathology
Our second hypothesis, that the severity of ADHD symptoms is associated with severity in ED symptoms and greater general psychopathology, was supported by our findings. Our results showed a positive association between the frequency of binge eating episodes and ADHD symptoms in the total sample, as well as in the BN, BED and EDNOS group. These findings are in agreement with previous research  and suggest that inattention and impulsivity may trigger eating disorders, especially binge eating behaviours. However, these findings are not consistent with a previous study  which found that ADHD severity symptoms were not related to the severity of ED symptoms.
Regarding eating symptomatology, our results showed associations between ADHD symptoms and EDI-2 scores. In the total sample, a positive association was found between the EDI-2 total score, the Interoceptive awareness subscale and ADHD symptomatology, which may suggest that an altered Interoceptive awareness combined with the EDI-2 total and with a poorer self directive personality, increases comorbid psychopathology, which is also associated with ADHD symptoms .
Another emergent finding was that perfectionism and ADHD symptomatology presented a negative association, i.e. the lower the perfectionism of a subject, the higher the number of ADHD symptoms. This finding goes along with the ED literature, since a perfectionism pattern and a disposition towards over-control are much more related to restrictive ED behaviors such as presented in anorexia, than the binge eating/purging conducts presented in binge eating/purging EDs .
Additionally, previous studies in ADHD literature reported that obsessive-compulsive and hostility are frequently found in ADHD patients [2, 36]. Correspondingly, both features are also present in patients with eating disorders and are positively associated with the increasing of the severity of the disorder. In our study we found a positive relation between Hostility and obsessive-compulsive patterns and ADHD symptoms, which re-iterates that both disorders have similar comorbid psychopathologies .
Personality traits and ADHD
As we know from research, adult ADHD patients share the same spectrum of personality traits as ED patients. Subjects meeting the ADHD diagnosis showed, in comparison with community subjects, higher scores on Neuroticism-Anxiety, Impulsive-Sensation Seeking and Aggression-Hostility in the Zuckerman Kuhlman Personality Questionnaire (ZKPQ) . Our results showed that ADHD symptomatology was associated with some personality scales, ADHD symptoms showed a positive association with Novelty Seeking and a negative association with Self-Directedness. These results are in line with other studies that have found specific links between Novelty Seeking and impulsivity/hyperactivity on one hand, and low Self-Directedness and inattention on the other hand [45, 46]. The negative association between ADHD symptoms and Self-Directedness may represent global lack of personal and social maturity and may reflect deficits in effortful control and executive functioning , but also to poorer outcome [45, 47].
In the AN group, the ADHD symptomatology was associated with high Cooperativeness and lower Reward Dependence and Self-Directedness. This personality profile has been described in the literature as the "maladaptative" profile and generally presented with the highest values for ED symptomatology and impulsive behaviors .
The present study should be evaluated within the context of several limitations. First, only female patients were included, so future studies should also considerer male ED patients. Second, compared to the binge/purge ED group, the AN group was rather small, which could have hidden some interesting findings. Further studies should include more AN patients to compare both the restrictive versus the binge/purging subtypes. Thirdly, this study is limited by the lack of information regarding psychiatric co-morbidity (mainly affective, anxiety and personality disorders). Finally, we assessed the frequency of adult ADHD symptoms by means of a self-rating screening instrument, which might contribute to an overestimation of ADHD symptoms and might explain the elevated prevalence of ADHD symptomatology in the study sample. In the same way, the presence of childhood ADHD was not assessed, which would have been a prerequisite for an ADHD diagnosis in adulthood. Then future studies focusing on the prevalence of ADHD, rather than the frequency of its symptomatology, should be conducted in ED patients. Personality functioning was also based on self-report measures. Thus, future studies might also include performance-based or neuropsychological tasks (i.e. Stroop task or CPT-II test) in order to shed some light on the impulsive behaviour characterizing both binge/purge ED patients and ADHD patients.