Eating disorders and obesity are common in ADHD.
1. ADHD and overweight/obesity/obesity
1.1. ADHD twice as common in obesity
The prevalence of ADHD is higher in people with extreme obesity than in the general population. An extremely long duration study over 33 years found that 41.4% of all males who had ADHD-C as a child developed massive obesity as adults, compared to only 21.6% of those without a childhood ADHD diagnosis. The doubling of the prevalence of obesity in ADHD sufferers has occurred (albeit at extremely different starting levels) in the USA from 21.6% without ADHD to 41.4% with ADHD as well as in Germany from 10.2% without ADHD to 22.1% with ADHD.
An Israeli cohort study found obesity to be almost twice as common in adolescents with severe ADHD as in those not affected, at 13.5%, and about 30% more common in those with mild ADHD than in those not affected.
ADHD is a significant risk factor for the development of obesity. Impulsivity in ADHD and increased BMI share genetic and neurophysiological correlates. ADHD, alcohol dependence, insomnia, and heavy smoking correlate with increased body fat.
Attention problems and hyperactivity correlated positively with food responsiveness, emotional overeating, desire to drink, and slowing down to eat. Attention problems reduced enjoyment of food. Conversely, eating behavior did not appear to be causative of ADHD. Normal overweight (below obesity/obesity) is also not thought to increase the likelihood of ADHD.
Another long-term cohort study in the USA found a linear correlation between the number of ADHD symptoms and the factors waist circumference, BMI, obesity, diastolic blood pressure and systolic blood pressure. An Israeli study also suggests this.
The comorbidity of ADHD was 58% in a study of hospitalized extremely overweight children.
Among 155 adult women in Brazil with a BMI > 39, an ADHD rate of 28.3% was found. Binge-eating, bulimia, and depression were also more common than average. The ADHD likelihood was thus 6.4-fold higher than the 4.4% prevalence expected in adults.
Similarly, the body mass index of ADHD sufferers is above average.
One study found no association of ADHD with BMI at age 9 or 13. However, children with ADHD at age 9 were significantly more likely to be overweight/obese than children without ADHD. However, this was not due to ADHD but to other child and parental factors such as female sex, low physical activity, overweight/obese parents, and prenatal smoking during pregnancy. A smaller study found no overlap between obesity and ADHD or autism spectrum disorders in 76 adolescents.
Among eating disorder sufferers, a meta-analysis found ADHD prevalence ranging from 1.6% to 18%. Comorbid ADHD was more common in the AN binge-eating/purging subtype and in the bulimia subtype than in the restrictive anorexia subtype.
Among ADHD sufferers, the meta-study found eating disorder lifetime prevalence ranged from zero to 21.8% among women with ADHD.
Massive obesity is at the same time associated with sleep apnea, shortened sleep and other sleep problems.
Conversely, sleep problems are the most common comorbidity in ADHD. See here Sleep problems in ADHD as well as Comorbidity in ADHD, there under sleep problems.
In adults without an ADHD diagnosis, daytime sleepiness correlates with the level of ADHD symptomatology.
1.2. ADHD treatment works against obesity
ADHD treatment can result in surprising weight loss success in massively obese patients. The ADHD-positive obese patients lost over 12% weight per year under typical ADHD medication.
For comparison: according to the current standard, a therapy against obesity is successful if the weight gain is not higher than 5% per year.
Other studies also enriched of a decrease in excessive BMI due to ADHD treatment in ADHD sufferers.
1.3. Obesity and addictive behavior
About half of all overweight people who have had a stomach reduction develop another addiction afterwards. This impressively proves that obesity is an addiction consequence.
That ADHD causes a massive disruption of the reward system, with the result that rewards that are more distant are significantly less interesting compared to non-affected individuals, is well known. Food can provide this instant gratification.
In ADHD, the overall addiction potential is significantly increased. This applies to legal addictive substances such as smoking, caffeine, alcohol or food as well as illegal addictive substances such as marijuana, amphetamines or cocaine.
Nicotine and caffeine are stimulants, as are typical ADHD medications.
Amphetamines, cocaine and marijuana - in specific forms - are effective as drugs.
The difference between an addictive substance and a drug is that addictive substances (including nicotine) have a rapid onset and address a very high number of the respective receptors, whereas drugs rise and fall slowly, occupy only a small portion of the receptors and therefore do not cause intoxication-like states. As with any substance; the dose makes the poison.
2. ADHD and eating disorders
Eating disorders are 3.6 times more common in girls with ADHD than in those not affected.
2.1. Binge eating twice as common
Eating disorders such as binge eating (very roughly, binge eating without vomiting) are also suspected to correlate with ADHD and contribute to weight problems.
In obese patients (BMI > 30), ADHD doubles the likelihood of adding binge eating and increases the probabilities of other eating disorders.
Among 150 adult women with a BMI > 39, an ADHD rate of 28.2% was found. Binge-eating, bulimia and depression were also more common than average.
2.2. Bulimia nervosa 6 - 8 times more common in women with ADHD
Bulimia nervosa (very roughly, binge eating with vomiting) is found in 11% to 12% of adult women with ADHD (according to DSM-III-R criteria) compared with about 1% to 3% of women without ADHD. There are no differences in men and children. Assuming a 1.5% prevalence of bulimia nervosa, this would result in an 8-fold increase in frequency for ADHD-affected women.
2.2. Anorexia 2.2 times more common in ADHD
ADHD-affected girls and women are “only” 2.2 times more likely to experience anorexia/anorexia (very roughly, vomiting without binge eating) than girls and women without ADHD.
3. ADHD and diabetes
Of 677,587 German children and adolescents, 16,833 received an ADHD diagnosis (2.5%), while 3668 were treated for type 1 diabetes mellitus with insulin (0.05%). In the subgroup of those with diabetes, 153 children (4.2%) also had an ADHD diagnosis. This suggests that ADHD sufferers have a greatly increased prevalence of type 1 diabetes and vice versa.
4. Cortisol, metabolism and body fat
Glucocorticoids (such as cortisol) have a central role in the regulation of carbohydrate metabolism by influencing gluconeogenesis.
Glucocorticoids also initiate and regulate a variety of digestive enzymes, the expression of membrane-bound transporter proteins, and proteins that are instrumental in gluconeogenesis.
Cortisol increases the success of pleasurable or compulsive activities (ingestion of sucrose, fat and drugs, or cycling races). This motivates the intake of “comfort foods”.
Cortisol systemically increases fat deposits in the abdomen. This causes
- An inhibition of catecholamines in the brainstem and
- An inhibition of CRH expression in the hypothalamus, which subsequently inhibits ACTH
Cortisol acts on adipose tissue by means of insulin
- Insulin resistance
Cortisol increases adrenaline-induced lipolysis (fat cleavage, fat digestion).
Impairment may be exacerbated by decreased ACTH levels.
It is possible that this correlation is reversed in severely overweight individuals (see below).
- While chronic stress and high glucocorticoids increase body weight gain in rats, in humans it causes either increased food intake and weight gain or decreased food intake and weight loss.
- Several studies show a correlation between cortisol stress response and waist-to-hip ratio, such that a low cortisol stress response is associated with a low waist-to-hip ratio (low waist) whereas a high cortisol stress response is associated with a high waist-to-hip ratio (high waist).
- Abnormalities of lipid metabolism (hypertriglyceridemia) that are more common in type A personality can be eliminated by ACTH administration but not by cortisol administration.
The described ACTH effect would be consistent with the present hypothesis of underreactivity of the HPA axis in type-A.
In ADHD sufferers of type A (then: ADHD-HI = with hyperactivity) a genetic predisposition or permanent stress could be
→ have led to prolonged increased CRH release,
→ which triggers CRH receptor downregulation,
→ which causes underactivation of the pituitary gland,
→ which triggers reduced ACTH release,
→ which causes decreased adrenal gland activity,
→ resulting in a reduced output of cortisol,
→ which is why, when the HPA axis is activated at the end of a stress response, only the MR but not the GR receptors are addressed,
→ which results in the HPA axis not being shut down cleanly.
Norepinephrine levels in the OFC and amygdala correlate with activation of the HPA axis in healthy individuals. In contrast, this correlation is inverted in severely overweight people.
The endocrine stress responses of noradrenaline and cortisol run in parallel. Thus, in ADHD-HI (with hyperactivity), not only the cortisol stress response but also the noradrenaline stress response is reduced.
- Obesity is characterized by high oxidative stress and inflammation. Inflammation is inhibited by cortisol. A low cortisol stress response results in reduced inhibition of inflammation.
5. Links between ADHD and eating disorders
5.1. Emotional dysregulation and impulsivity
An important link between eating disorders (especially binge eating) and ADHD appears to be the symptoms of emotional dysregulation and impulsivity.
Both ADHD and obesity are characterized by deviations in dopamine balance. While disturbed eating behavior correlated with increased plasma dopamine levels in women, blood dopamine levels were reduced in men with eating disorders.