The present study revealed that 30% of a sample of patients enrolled in a weight loss program reported symptoms consistent with ADHD. Relative to their counterparts screening negative, patients screening positive for ADHD lost less weight following a structured behavioral weight loss program, were half as likely to lose clinically significant weight (at least 5% of weight), consumed fast food more often, were more likely to eat in response to negative moods, perceived weight loss skills as more difficult, and reported lower eating self-efficacy. These patients also reported nearly 5 times as many short-lived weight loss attempts (i.e., lasting less than 3 days) and twice the number of sustained weight loss attempts (i.e., lasting more than 3 days) as their counterparts without symptoms, although the latter was not statistically significant. In spite of these differences, ADHD-positive patients were not more likely to skip meals and they did not report less frequent physical activity.
The finding that 30% of patients reported symptoms of ADHD is consistent with previous studies of obese clinic samples. Fleming and colleagues (15
) administered standardized measures of ADHD to 75 consecutive patients (BMI ≥ 35) referred for non-surgical treatment of obesity in a Canadian weight loss clinic (15
). On the Conner's Adult ADHD Rating Scale (29
), 30.7% of their sample showed clinical elevations on the ADHD Index subscale. Because childhood symptoms are necessary for the diagnosis of ADHD in adulthood, they administered the Wender Utah Rating Scale and 38.6% of the sample met criteria. Overall, 26.7% of their sample reported symptoms consistent with a diagnosis of ADHD in both childhood and adulthood. Inattentive symptoms, but not hyperactive symptoms of ADHD, were most frequently reported. Similar findings were reported in a study by Altfas (14
), where medical charts of 215 weight loss clinic patients were reviewed retrospectively to investigate the prevalence of ADHD and to test the association between ADHD diagnosis and weight loss following treatment. To be diagnosed with ADHD, patients had to report 6 or more DSM-IV inattentive symptoms as well as report symptoms starting prior to 12 years old in semi-structured clinical interviews of DSM-IV diagnostic criteria. The prevalence of ADHD was 27.4%, six times higher than what has been observed in the general population, i.e., 4.4% (14
). Among those with class III obesity, 42.6% met criteria for ADHD. All patients with the ADHD diagnosis had inattentive sub-type; none had the hyperactive-impulsive sub-type. Patients with ADHD also had a significantly higher baseline BMI than those without ADHD (mean = 39.6 vs. 34.2 kg/m2
) and lost just over half of the weight (mean = 3.34%) of their counterparts without ADHD (mean = 5.59%). Although ADHD-positive participants in the present study were not heavier at baseline, as in Altfas (14
), they lost just over half of the weight as their counterparts without ADHD symptoms.
Adults screening positive for ADHD appear to have greater difficulty losing weight in spite of more frequent attempts to do so. In the present study, ADHD-positive participants reported an average of 10 short-lived weight loss attempts (i.e., lasting less than 3 days) in the previous year compared to about 2 short-lived attempts as reported by ADHD-negative participants. Deficits in working memory and persistence, which can manifest in poor follow through with intentions, plans, and goals (9
) may be a factor. When combined with a greater tendency toward impulsivity, this might result in greater vulnerability to the lure of fad diets and greater reactivity to external cues to overeat, which could lead to diet relapse. Emotional reactivity may also be a factor. ADHD-positive participants reported a greater tendency to eat in response to negative moods including sadness, boredom, tiredness, anger, and anxiety.
ADHD-positive participants rated weight loss skills as more challenging than their ADHD-negative counterparts. Weight loss skills such as tracking calories, keeping a diet diary, planning meals ahead of time, and other skills require a degree of conscientiousness, memory, and organizational skills, areas that are often deficient in ADHD (9
). Additional guidance and support around applying these skills to weight management may be indicated for adults with ADHD.
Referral for evaluation and treatment of ADHD should be a consideration for adults with signs of ADHD who present for weight loss treatment. A recent clinical observational study found that severely obese patients with ADHD who received pharmacological treatment for their ADHD had a 12% weight loss over 466 days of medication relative to a 2% weight gain in ADHD controls who refused or discontinued medication (30
). Weight loss might be enhanced further if pharmacological treatment for ADHD is supplemented with a behavioral weight loss program. Randomized trials are needed to evaluate the use of ADHD medication and the combination of medication and behavioral treatment on weight loss in this population.
The present study has a number of limitations, with the most important being that self-report data was collected after participants completed the treatment program which means that responses on non-trait variables were likely impacted by the program. Data for self-efficacy, diet habits, physical activity, and perceived difficulty reflect how participants were feeling following, not prior to, the structured weight loss program. Responses to the ASRS were not likely impacted as items refer to stable patterns of behavior experienced by participants. However, the ASRS was used to predict outcomes from weight treatment that occurred previous to the ASRS being administered, where typically predictors are assessed prior to the outcome they are being used to predict.
Second, the ASRS does not diagnose ADHD but rather is a screener for ADHD symptoms in adults (18
). Scores of 4 or greater on the ASRS have been shown to be highly predictive of ADHD diagnosis (18
). The ASRS is a quick and simple screening tool that is more feasible than diagnostic interviews in medical settings such as a weight loss clinic where assessment time is very limited. Whether symptoms are a function of an underlying medical or other psychiatric condition is not possible to discern, and the ASRS does not assess childhood symptoms. For these reasons, the ASRS likely errs toward over-estimating ADHD. Two studies have reported similar rates of ADHD in samples that included all enrolled patients and used more intensive assessment of ADHD diagnosis (e.g., (14
)). Weight loss clinics that incorporate the ASRS into their pre-treatment evaluation should interpret scores cautiously and refer positive screens for more comprehensive diagnostic assessment. Although depression is highly co-morbid with obesity and ADHD, in the present study, individuals with ADHD symptoms were not more likely to be depressed (p = .34).
A third limitation is that reports of past behavior might be less accurate among adults with symptoms of ADHD given that they might have greater difficulty recalling past behavior (e.g., number of weight loss attempts in the past year). To explore this phenomenon, participants were asked to rate the accuracy of their weight loss history recall on a scale of 1 to 10. ASRS-positive participants rated themselves significantly less accurate at recalling their history (mean = 4.9, sd= 2.6) than ASRS-negative participants (mean = 6.8, sd=1.9; p=.003). As such, this variable was entered as a covariate in the model of relevant items. Fourth, although all patients were approached after completing the program, the sample does not include all patients only the 40% who agreed to participate in the study. Although the focus of the study on ADHD was not mentioned in study materials, individuals volunteering to participate may not have been representative of the entire population of people who participated in the weight loss program. Finally, the sample size was fairly small, limiting power to answer some of the questions of interest. Nevertheless, our findings suggest that future research of the impact of ADHD on weight loss and related behaviors on larger samples is merited.
The association between ADHD and risk for obesity is now well-established. Our findings and others strongly suggest that ADHD may be a risk factor for treatment resistant obesity. Further research is needed to clearly establish this as well as the mechanisms of weight treatment failure in these individuals. Assessment of ADHD using screening devices such as the ASRS is recommended in clinical settings to identify patients who may benefit from ADHD assessment and treatment and who might require extra support around attention-related challenges during their weight loss attempt. Controlling ADHD symptoms might be a necessary first step to addressing weight control in this population.