Epidemiology of Eating Disorders

epidemiology of eating disorders for the psychiatry board exam and PRITE

In this blog, we will take a look at eating disorders including Binge Eating Disorder, Bulimia Nervosa, and Anorexia Nervosa. Let’s review the epidemiology of these disorders. This information should help you on the PRITE and quite possibly on the psychiatry board exam, so pay attention!

What is the most common eating disorder?
Binge Eating Disorder (2-25%) > Bulimia Nervosa (1-2% in women) > Anorexia Nervosa (0.5-1.0 % in women)

Which of the above disorders has the lowest female to male ratio?
Binge Eating Disorder (60% in females) – 90% of patients with either anorexia or bulimia are female

Which of the above disorders is more heritable?
Anorexia (concordance rate of 56% compared to 8-23% in Bulimia)

Is the incidence of anorexia and bulimia increasing, decreasing, or unchanging?

Patients usually have an older age of onset for this eating disorder:

Anorexia typically has an age of onset between:
13 to 20 years of age

True or false: anorexia nervosa occurs predominantly in upper economic classes.
False (earlier surveys reported this finding but more recent surveys have failed to confirm this finding. Anorexia is seen in 0.5% of adolescent girls and seems to be more common in whites, females, dysfunctional family relationships, people with a FH of anorexia, and in professions that require thinness)

Anorexia nervosa occurs _____ times more frequently in females than males.
10-20 times (4-6% of those affected are male)

Mortality rates for anorexia nervosa at 30 years after presentation for treatment are: [1%, 3%, 5%, 20%, 35% or 50%]
20% – Kaplan and Sadock give a mortality rate between 5-18 %, likely depending on time from initial presentation for treatment. They give a mortality rate after 10 years of approximately 7%. Overall it has the highest mortality rate of any psychiatric disorder.

White girls are more likely to have anorexia, characterized by ______ while black girls are more likely to have anorexia, characterized by _______.
White girls – restricting
Black girls – bingeing (and purging)

True or false: being overweight is a risk factor for black girls but not white girls for developing an eating disorder.
True – white girls that perceive themselves to be overweight are at risk of an eating disorder

Which relationship is the strongest predictor for obesity?
A. Having an obese sibling
B. Having an obese spouse
C. Having an obese same-sex male friend (male-male friendship)
D. Having an obese same-sex female friend (female-female friendship)
E. Having an obese opposite-sex friend (male-female friendship)

Answer: C – having an obese sibling or spouse are predictors of obese, but not nearly as predictable as having an obese male-male friendship. A recent study looked at relationships and risk of obesity and found that for same-sex relationships, the overall probability of obesity in one person increased by 70% if the other person became obese. When you break the relationships down, you find that the increase in risk for obesity is 100% if it is a male-male friendship and only 40% (and not significant) if it is a female-female friendship.

Who is at most risk for morbidity and mortality: restricting type of anorexia, purging type of anorexia, binging/purging type of bulimia, or binging/restricting type of bulimia?
Purging type of anorexia – complications from purging as well as starvation

What is the mortality rate of anorexia nervosa?
5% (from suicide, electrolyte imbalances, sudden death, and starvation) – a more recent article give an estimate of 0.56% per year. The Johns Hopkins source gives a mortality between 5-18%; I assume this figure is lifetime mortality. Anorexia is the psychiatric disorder with the highest mortality (10% in another source).

True or false: the majority of patients with anorexia have a poor outcome.
False – 50% have a good outcome, 25% an intermediate outcome, and 25% a poor outcome

Most common comorbid psychiatric disorder in either anorexia or bulimia:
Major depression (in over 67% of patients), followed by anxiety disorders (in about 50-66% of patients) – I believe that depression is overall the most common disorder seen in first-degree relatives of patients with anorexia too. When someone is severely underweight and/or starving, their symptoms mimic major depression, so it is difficult and not recommended to make the diagnosis of depression in a severely underweight anorexic. Need to refeed the patient to make an accurate diagnosis. Also, while anxiety disorders are common, equally common is anxiety just before or after feeding (I often give 1-2 mg of valium 30 minutes before a meal to help with this anxiety).

Patients with bulimia have the highest risk of having which of the following personality disorders? [Avoidant, Histrionic, Borderline, Schizotypal, Narcissistic]
Borderline Personality Disorder

People with anorexia nervosa binging-purging type are more likely to have which of the following comorbid conditions than those with the restrictive type? [Anxiety, Depression, Malnutrition, Substance abuse]
Substance abuse – In general, people with anorexia, restricting type tend to have comorbid disorders involving the traits of perfectionism and/or obsessiveness. OCD occurs in about 20% of these patients, while a high prevalence of OCD and OCPD characteristics has been found in first-degree relatives. Patients with bulimia and/or anorexia with the bingeing-purging subtype are clearly marked with the trait of impulsivity. About 1/3 of these patients have a substance abuse disorder and the cluster B (impulsive) personalities frequently occur. Finally, besides substance abuse, other impulsive behaviors such as cutting and suicide attempts occur quite often.

That’s all for today. Thanks for reading, and I hope this review on the epidemiology or eating disorders, including Binge Eating Disorder, Bulimia Nervosa, and Anorexia Nervosa will really help you on the PRITE and psychiatry board exam!


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