While these three diagnostic categories encompass a lot of the people with an eating disorder, there are also quite a number of people who present with an eating disorder but don’t quite meet the criteria required for one of those three diagnoses.
Such people would instead be classified under the broader Other Specified Feeding or Eating Disorder (OSFED), because they present with clinically significant eating disorder symptoms and functional impairment but do not meet criteria for one of the three stand-alone eating disorders.
One subtype of OSFED to emerge from the latest Diagnostic and Statically Manual for Mental Disorders (DSM-5) is purging disorder.
What is Purging Disorder?
Purging disorder is characterized by repeated episodes of purging in the absence of binge eating in individuals who are not underweight. 1Keel, P. K. (2019). Purging disorder: Recent advances and future challenges. Current opinion in psychiatry, 32(6), 518
Let’s break down this definition a little further.
Purging in this context means the forceful evacuation of matter from the body.
It can take a number of different forms, the most common being self-induced vomiting.
Using laxatives, diuretics, or other medications are also forms of purging.
Binge eating, a core feature of binge-eating disorder and bulimia nervosa, refers to eating a large amount of food in a discrete period, accompanied by a sense of loss of control.
This is different from overeating, which involves eating slightly more than usual but still feeling in control.
Underweight in the context of purging disorder is defined as an adult body mass index < 18.5kg/m2 or, for younger people, a BMI < 5th percentile for age and sex.
Confusing Purging Disorder with Anorexia and Bulimia Nervosa
Although there are key similarities between purging disorder, anorexia nervosa, and bulimia nervosa, there are also important differences that need to be understood.
The main feature that distinguishes purging disorder from anorexia nervosa is the criterion related to body weight.
People with anorexia nervosa are considered underweight, whereas people with purging disorder are not underweight.
The main feature that distinguishes purging disorder from bulimia nervosa is the binge eating behaviour.
People with bulimia nervosa engage in repeated episodes of binge eating, and their purging behaviour is usually practiced to eliminate those calories consumed during the binge. In contrast, people with purging disorder do not binge, otherwise they would be classified with bulimia nervosa. Instead, they purge regularly after eating, in the absence of a binge.
This means that purging disorder falls somewhere in between bulimia nervosa and anorexia nervosa.
A recent meta-analysis of purging disorder also found some other important differences (and similarities) between purging disorder and anorexia and bulimia nervosa2Smith, K. E., Crowther, J. H., & Lavender, J. M. (2017). A review of purging disorder through meta-analysis. Journal of abnormal psychology, 126(5), 565
Compared to anorexia nervosa, purging disorder:
- Reported a later age of illness onset
- Responded to treatment much better
- Hadn’t sought treatment as much in the past
- Purged more frequently and severely
- Engaged in fewer subjective binge episodes
- Had higher levels of dietary restraint
- Reported higher levels of substance abuse and self-esteem
Similar to anorexia nervosa, purging disorder had a comparable duration of illness, and comparable levels of suicidality, depression, anxiety, perfectionism, and body dissatisfaction.
Compared to bulimia nervosa, purging disorder had:
- A later age of onset
- Better treatment outcomes
- Lower depression, impulsivity, and perfectionism
- Higher self-esteem
- Lower frequency of purging
- Lower body dissatisfaction
Similar to bulimia nervosa, purging disorder had a comparable duration of illness, treatment history, suicidality, substance use, anxiety, dietary restraint levels, and subjective binge eating frequencies.
A growing amount of research is being conducted to better understand the epidemiology of purging disorder. Let’s take a look at some of the important statistics related to purging disorder below.
- In one follow-up study of 9,031 US girls aged 9-15 years, the lifetime prevalence of purging disorder was 6.2%. 3Glazer KB, Sonneville KR, Micali N, Swanson SA, Crosby R, Horton NJ, et al. The Course of Eating Disorders Involving Bingeing and Purging Among Adolescent Girls: Prevalence, Stability, and Transitions. J Adolesc Health. 2019 2;64(2):165–71.
- The point prevalence of purging disorder by age group in this study was as follows:
- 0.4% in girls 9-12 years
- 1.9% in girls 13-15 years
- 2.5% in girls at 16-18 years
- 2.5% in women at 19-22 years
- 2.5% in women 23-27 years
- 1.3% in women 28 years or older
- In 5,072 Australian adolescent girls and boys, the prevalence of purging disorder was 3.2% 4Mitchison D, Mond J, Bussey K, Griffiths S, Trompeter N, Lonergan A, et al. DSM-5 full syndrome, other specified, and unspecified eating disorders in Australian adolescents: prevalence and clinical significance. Psychol Med. 2019 5 2:1–10
- Around 36% of people with purging disorder are male5Hay P, Mitchison D, Collado AEL, Gonzalez-Chica DA, Stocks N, Touyz S. Burden and health-related quality of life of eating disorders, including Avoidant/Restrictive Food Intake Disorder (ARFID), in the Australian population. J Eat Disord. 2017;5:21[ref].
- Among outpatient samples, anorexia nervosa outnumbers purging disorder 7:1 and bulimia nervosa outnumbers purging disorder 6:1[ref]Vo M, Accurso EC, Goldschmidt AB, Le Grange D. The Impact of DSM-5 on Eating Disorder Diagnoses. Int J Eat Disord. 2017 5;50(5):578–81
- Among inpatient samples, the anorexia nervosa – purging disorder ratio is 17:1 and the bulimia nervosa – purging disorder ratio is 10:16Nakai Y, Nin K, Noma S, Teramukai S, Fujikawa K, Wonderlich SA. Changing profile of eating disorders between 1963 and 2004 in a Japanese sample. Int J Eat Disord. 2018.
Causes of Purging Disorder
The precise causes of purging disorder are as yet unclear.
However, there have been some follow-up studies that have identified possible risk factors for purging disorder.
The risk factors that have been identified include:
- Childhood overweight
- Body dissatisfaction
- More frequent dieting
- More positive thinness expectancies
- Elevated emotional distress
Consequences of Purging Disorder
The consequences of purging disorder can be quite severe, and they resemble the consequences experienced among people with bulimia nervosa.
The adverse consequences usually occur as a result of the frequent purging behaviours practiced, but restrictive eating patterns can also contribute to some of these side-effects.
- Electrolyte imbalance
- Erosion of tooth enamel
- Oesophagus damage
- Loss of menstruation for females
- Stomach rupture
- Peptic ulcers
- Gum disease
- Cardiac arrest
- Depressed mood
- Anxious symptoms
- Substance use and abuse
- Suicidal thinking/self-help behaviour
- Low self-esteem
- Sexual dysfunction
- Interpersonal withdrawal
- Feelings of isolation
How do we Treat Purging Disorder?
Unfortunately, research on the treatment of purging disorder is very limited, so we do not yet have a strong understanding of what does and does not work for this population.
Some small studies have shown that interventions based on cognitive-behavioural principles may help people with purging disorder, but there is insufficient evidence as of yet to make any strong conclusions 7Riesco N, Aguera Z, Granero R, Jimenez-Murcia S, Menchon JM, Fernandez-Aranda F. Other Specified Feeding or Eating Disorders (OSFED): Clinical heterogeneity and cognitive-behavioral therapy outcome. Eur Psychiatry. 2018 10;54:109–16.
We urgently need more rigorous research to understand what the best treatment approach is for purging disorder.