What is comorbidity?
A comorbidity is any coexisting health condition, which can also be described as coexisting or co-occurring conditions. Comorbidities can sometimes interact with each other, but they can also exist entirely independently.
Comorbidities are often chronic conditions and can include physical and mental health issues. It’s possible to have several comorbidities at the same time, which is sometimes known as multimorbidity. (1)
What’s the difference between comorbidity and complication?
Comorbidities are co-existing conditions that develop independently of one another. They can share the same risk factors but don't directly cause one another. For example, anorexia nervosa may increase your risk of developing anxiety and depression.
A complication is a medical condition that develops from another condition or from treatment for another disorder.
What causes comorbidities?
While some comorbidities occur together at random, others are connected via shared behavioral, genetic, and/or environmental risk factors. Comorbidities can be connected through: (1)
- Overlapping risk factors
- Chance occurrence between two conditions
- One disorder results from complications from another
- A third condition causes both comorbidities.
Comorbidities of eating disorders
In a nationally representative survey of people with eating disorders, the following percentages met the criteria for a co-occurring disorder (2):
- 56% of those with anorexia nervosa
- 79% with binge eating disorder
- 95% with bulimia nervosa
What physical comorbid conditions are common with eating disorders?
The medical comorbidities associated range from mild to severe and potentially life-threatening, with complications affecting all body systems, including the reproductive, cardiac, metabolic, and gastrointestinal systems. (3) These comorbidities can place people with eating disorders at increased risk of medical instability and death, as well as impact treatment and recovery.
Studies indicate there is a high rate of comorbidity between eating disorders and functional gastrointestinal (GI) disorders including anorectal, esophageal, and bowel disorders. There is a suggestion that this could be the result of structural changes, for example, findings from a review study indicate that structural changes in the GI tract of those with anorexia nervosa impacted their ability to swallow and absorb nutrients. (3)
The comorbidity between eating disorders and chronic GI disorders can lead to eating disorders being misdiagnosed, particularly in adolescents, due to the crossover of symptoms.
Metabolic Syndrome and diabetes
Metabolic syndrome refers to a group of factors that increase the risk for diabetes, heart disease, stroke, and other related conditions. Binge eating behaviors exhibited in binge eating disorder and bulimia nervosa have been linked to increased rates of metabolic syndrome.
While type 1 diabetes is considered a risk factor for eating disorder development, those with binge eating disorder and bulimia nervosa have an increased risk of type 2 diabetes. Furthermore, research indicates that binge eating disorder is the most prevalent eating disorder in those with type 2 diabetes. (3) Another study has found that binge eating disorder has a significant effect on metabolic abnormalities including poor glycaemic control and higher levels of cholesterol.
When it comes to cardiovascular issues and eating disorders, anorexia nervosa has been the focus of the majority of research, given the increased risk of cardiac failure due to electrolyte imbalances, severe malnutrition, and dehydration. (3)
A review found that over 80% of people experience cardiovascular issues shortly following the development of anorexia nervosa, including bradycardia (slow heart rate), hypotension (low blood pressure), arrhythmia, cardiac arrest, and pericardial effusion (a build-up of fluid around the heart). (3)
Infertility and increased rates of reproductive health issues are strongly associated with eating disorders, including poor birth outcomes, gestational diabetes, increased cesarean deliveries, complications during childbirth, and miscarriages. (3)
Menstrual irregularities are also common in those with eating disorders. While amenorrhea (loss of periods) is common in those with anorexia nervosa, irregular periods may be more prevalent in those with bulimia nervosa. Menstrual irregularities in those l with binge eating disorder are likely to develop as a result of polycystic ovarian syndrome, for which they are more at risk. (3)
Other physical comorbidities
Other physical comorbidities of eating disorders include, but are not limited to (3,4)
- Joint pain
- Bone issues, including osteoporosis and osteopenia
- Oral health problems, including tooth erosion and gum disease
- Impaired cognitive function
What psychological disorders commonly co-occur with eating disorders?
Many studies have demonstrated the high rate of comorbid psychological disorders in those with eating disorders. For example, a recent study of women with eating disorders found that 94% of the participants had a co-occurring mood disorder and 92% were struggling with a depressive disorder. (2)
A narrative review of European studies found that the most frequent co-occurring mental disorders are anxiety disorders (more than 50% of those with eating disorders), mood disorders (more than 40%), self-harm behaviors (around 10%), and substance use disorders (more than 4%). (5)
It’s worth mentioning that studies into the psychiatric comorbidity in eating disorders show a wide variability. For example, studies that researched the prevalence of co-existing personality disorders with eating disorders range from 27% to 93% (5)
Co-occurring mental health conditions can be challenging for eating disorder recovery, which at times can lead to misdiagnosis, unsuitable and inadequate treatment, and relapse.
Common psychological comorbidities of eating disorders
Anxiety disorders - such as generalized anxiety disorder, panic disorder, separation anxiety, and specific phobias, amongst others - are believed to be the most common co-occurring psychological disorder with eating disorders. Research indicates that anxiety disorders affect approximately:
- >47% of those with anorexia nervosa
- >65% of those with binge eating disorder
- >80% of those with bulimia nervosa
The risk factors for eating disorders and anxiety disorders are similar. Both disorders typically affect individuals with neurotic and/or perfectionist tendencies, as well as those that struggle with rigidity in their behaviors and beliefs. (6)
Depression and other mood disorders (such as bipolar disorder) often coexist with eating disorders. Mood disorders can occur as a result of malnutrition and the impact of eating disorders, develop as an ineffective method of coping with their disordered eating, or both. (6) While figures vary, research estimates that mood disorders affect:
- >40% of those with anorexia nervosa
- >45% of those with binge eating disorder
- >70% of those with bulimia nervosa
Obsessive-compulsive disorder (OCD)
The traits that put a person at risk of developing an eating disorder also increase the risk for the development of OCD. These traits include perfectionism, rigidity, and meticulousness, as well as difficulty coping with the stress caused by changes. (6)
Eating disorders often involve both compulsive behaviors and obsessive beliefs when it comes to food. Research suggests that those with eating disorders have significantly higher rates of co-occurring OCD. (7)
Borderline personality disorder (BPD)
BPD affects anywhere between 14 to 53% of people with an eating disorder. Both disorders share some similar characteristics including struggling with emotional regulation, distress tolerance, and interpersonal effectiveness skills. Also, individuals with BPD may engage in behaviors to avoid perceived or real rejection, with some of these being disordered eating behaviors.
Self-harming behaviors are common in those with eating disorders, with some studies indicating that over 61% of people with an eating disorder diagnosis report engaging in self-injury behaviors. (6)
Self-harming in people with eating disorders typically develop as a maladaptive coping mechanism for uncomfortable feeling and emotions. By contrast, in some, the disordered eating behaviors themselves are intended to be self-harm.
Other psychological comorbidities
Additional psychological comorbidities of eating disorders include: (3,6)
- Post-traumatic stress disorder
- Substance use disorder, including alcoholism
- Trichotillomania (a compulsive need to pull out one’s hair)
- Psychosis and schizophrenia
- Body dysmorphic disorder
Treating the person as a whole
No matter the diagnosis, research shows that the rates of long-term recovery are better if co-occurring conditions are treated simultaneously with the eating disorder. If co-existing conditions are not treated together by a multidisciplinary team that communicates with one another, root issues are not addressed.
It’s like picking the leaves from a weed, without tackling and destroying the root. The leaves simply grow back, just like the disordered eating behaviors return. Therefore eating disorders and their comorbidities must be treated together. A person needs to be treated as a whole entity.
So what does treating the whole person look like? It involves a multidisciplinary care team of experts which may include physicians, psychiatrists, nutritionists, and care partners that can deliver: (8)
- Early identification of comorbidities
- A treatment plan customized to the individual
- Collaboration between clinical, medical, and support staff
- Inclusion of the family in healing relationships
- Focus on the individual’s autonomy over their recovery
Coexisting conditions can make a person feel hopeless and even shameful. Treating the comorbidities alongside the eating disorder with compassion can help a person feel real hope for a full recovery.