Eating disorders - Causes

Causes
It is not known with certainty what causes eating disorders. It can be due to a combination of biological, psychological or environmental causes.

Biological

 * Genetic: Numerous studies have been undertaken that show a possible genetic predisposition toward eating disorders.
 * Biochemical:Eating behavior is a complex process controlled by the neuroendocrine system of which the Hypothalamus-pituitary-adrenal-axis (HPA axis) is a major component. Dysregulation of the HPA-axis has been associated with eating disorders, such as irregularities in the manufacture, amount or transmission of certain neurotransmitters, hormones or neuropeptides.
 * serotonin: a neurotransmitter involved in depression also has an inhibitory affect on eating behavior
 * norepinephrine is both a neurotransmitter and a hormone; abnormalities in either capacity may affect eating behavior
 * dopamine:which in addition to being a precursor of norepinephrine and epinephrine is also a neurotransmitter which regulates the rewarding property of food
 * leptin and ghrelin; leptin is a hormone produced primarily by the fat cells in the body it has an inhibitory effect on appetite by inducing a feeling of saiety. Ghrelin is an appetite inducing hormone produced in the stomach and the upper portion of the small intestine. Circulating levels of both hormones are an important factor in weight control. While often associated with obesity both hormones and their respective effects have been implicated in the pathophysiology of anorexia nervosa and bulimia nervosa.
 * immune system:studies have shown that a majority of patients with anorexia and bulimia nervosa have elevated levels of autoantibodies that affect hormones and neuropeptides that regulate appetite control and the stress response. There may be a direct correlation between autoantibody levels and associated psychological traits.
 * infection:PANDAS, is an abbreviation for Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections. Children with PANDAS "have Obsessive Compulsive Disorder (OCD) and/or tic disorders such as Tourette's Syndrome, and in whom symptoms worsen following infections such as "Strep throat" and Scarlet Fever." (NIMH) There is a possibility that PANDAS may be a precipitating factor in the development of Anorexia nervosa in some cases, (PANDAS AN).
 * lesions:studies have shown that lesions to the right frontal lobe or temporal lobe can cause the pathological symptoms of an eating disorder
 * tumors:tumors in various regions of the brain have been implicated in the development of abnormal eating patterns.
 * brain calcification: a study highlights a case in which prior calcification of the right thalumus may have contributed to development of anorexia nervosa.
 * somatosensory homunculus; is the representation of the body located in the somatosensory cortex, first described by renowned neurosurgeon Wilder Penfield. The illustration was originally termed "Penfield's Homunculus", homunculus meaning little man. "In normal development this representation should adapt as the body goes through its pubertal growth spurt. However, in AN it is hypothesized that there is a lack of plasticity in this area, which may result in impairments of sensory processing and distortion of body image". (Bryan Lask, also proposed by VS Ramachandran)
 * Obstetric complications. There have been studies done which show maternal smoking, obstetric and perinatal complications such as maternal anemia, very pre-term birth      (32<wks.), being born small for gestational age,  neonatal cardiac problems, preeclampsia, placental infarction and sustaining a cephalhematoma at birth increase the risk factor for developing either anorexia nervosa or bulimia nervosa. Some of this developmental risk as in the case of placental infarction, maternal anemia and cardiac problems may cause intrauterine hypoxia, umbilical cord occlusion or cord prolapse may cause ischemia, resulting in cerebral injury, the prefrontal cortex in the fetus and neonate is highly susceptible to damage as a result of oxygen deprivation this has been shown to contribute to executive dysfunction, ADHD, and may affect personality traits associated with both eating disorders and comorbid disorders such as impulsivity, mental rigidity and obsessionality. The problem of perinatal brain injury, in terms of the costs to society and to the affected individuals and their families, is extraordinary." (Yafeng Dong, PhD)

Psychological
Eating disorders are classified as Axis I disorders in the Diagnostic and Statistical Manual of Mental Health Disorders (DSM-IV). Published by The American Psychiatric Association. There are various other psychological issues that may factor into eating disorders, some fulfill the criteria for a separate Axis I diagnosis or a personality disorder which is coded Axis II  and thus are considered comorbid to the diagnosed eating disorder. Axis II disorders are subtyped into 3 "clusters", A, B and C.The causality between personality disorders and eating disorders has yet to be fully established. Some people have a previous disorder which may increase their vulnerability to developing an eating disorder. Some develop them afterwards. The severity and type of eating disorder symptoms have been shown to affect comorbidity. The DSM-IV should not be used by laypersons to diagnose themselves, even when used by professionals there has been considerable controversy over the diagnostic criteria used for various diagnoses, including eating disorders. There has been controversy over various editions of the DSM including the latest edition DSM-V due in May 2013.

Personality traits
There are various childhood personality traits associated with the development of eating disorders. During adolescence these traits may become intensified due to a variety of physiological and cultural influences such as the hormonal changes associated with puberty, stress related to the approaching demands of maturity and socio-cultural influences and perceived expectations, especially in areas that concern body image. Many personality traits have a genetic component and are highly heritable. Maladaptive levels of certain traits may be acquired as a result of anoxic or traumatic brain injury, neurodegenerative diseases such as Parkinson's disease, neurotoxicity such as lead exposure, bacterial infection such as Lyme disease or viral infection such as Toxoplasma gondii as well as hormonal influences. While studies are still continuing via the use of various imaging techniques such as fMRI; these traits have been shown to originate in various regions of the brain such as the amygdala and the prefrontal cortex  Disorders in the prefrontal cortex and the executive functioning system have have been shown to affect eating behavior.

Child maltreatment
Child abuse which encompasses physical, psychological and sexual abuse, as well as neglect has been shown by innumerable studies to be a precipitating factor in a wide variety of psychiatric disorders including eating disorders. Children who are subjugated to abuse may develop a disordered eating pattern in an effort to gain some sense of control or for a sense of comfort. Or they may be in an environment where the diet is unhealthful or insufficient.

Child abuse and neglect can cause profound changes in both the physiological structure and the neurochemistry of the developing brain. Children who as wards of the state were placed in orphanages or foster homes are especially susceptible to developing a disordered eating pattern. In a study done in New Zealand 25% of the study subjects in foster care exhibited an eating disorder. (Tarren-Sweeney M. 2006) An unstable home environment is detrimental to the emotional well-being of children, even in the absence of blatant abuse or neglect the stress of an unstable home can contribute to the development of an eating disorder.

Social isolation
Social isolation has been shown to have a deleterious effect on an individuals' physical and emotional well-being. Those that are socially isolated have a higher mortality rate in general as compared to individuals that have established social relationships. This effect on mortality is markedly increased in those with pre-existing medical or psychiatric conditions, this has been especially noted in cases of coronary heart disease. "The magnitude of risk associated with social isolation is comparable with that of cigarette smoking and other major biomedical and psychosocial risk factors." ( Brummett et al.)

Social isolation can be inherently stressful, depressing and anxiety provoking. In an attempt to ameliorate these distressful feelings an individual may engage in emotional eating in which food serves as a source of comfort. The loneliness of social isolation and the inherent stressors thus associated have been implicated as triggering factors in binge eating as well.

Parental influence
Parental influence has been shown to be an intrinsic component in developing the eating behaviors of children. This influence is manifested and shaped by a variety of diverse factors such as familial genetic predisposition, dietary choices as dictated by cultural or ethnic preferences, the parents' own body shape and eating patterns, the degree of involvement and expectations of their children's eating behavior as well as the interpersonal relationship of parent and child. This is in addition to the general psychosocial climate of the home and the presence or absence of a nurturing stable environment. It has been shown that maladaptive parental behavior has an important role in the development of eating disorders. As to the more subtle aspects of parental influence it has been shown that eating patterns are established in early childhood and that children should be allowed to decide when their appetite is satisfied as early as the age of two. A direct link has been proven between obesity and parental pressure to eat more.

Coercive tactics in regard to diet have not been proven to be efficacious in controlling a child's eating behavior. Affection and attention have been shown to affect the degree of a childs' finickiness and their acceptance of a more varied diet.

Peer pressure
In various studies such as one conducted by The McKnight Investigators, peer pressure was shown to be a significant contributor to body image concerns and attitudes toward eating among subjects in their teens and early twenties.

Eleanor Mackey and co-author, Annette M. La Greca of the University of Miami, studied 236 teen girls from public high schools in southeast Florida. "Teen girls' concerns about their own weight, about how they appear to others and their perceptions that their peers want them to be thin are significantly related to weight-control behavior," says psychologist Eleanor Mackey of the Children's National Medical Center in Washington and lead author of the study. "Those are really important."

Dieting among adolescents was also reported to being influenced by peer behavior. With many of those individuals on a diet reporting that their friends also were dieting. The number of friends dieting and the number of friends who pressured them to diet also played a significant role in their own choices.

Cultural pressure
There is a cultural emphasis on thinness which is especially pervasive in western society. There is an unrealistic stereotype of what constitutes beauty and the ideal body type as portrayed by the media, fashion and entertainment industries."The cultural pressure on women to be thin is an important predisposing factor for the development of eating disorders" (Bryan Lask, PhD)

Eating disorders in men
There has been an increasing rate of males suffering from various eating disorders including anorexia nervosa. There is a perceived stigma attached, as eating disorders are generally viewed as primarily affecting women. Among men the rates of eating disorders are higher in the gay and bi-sexual communities (Feldman & Meyer, 2007), yet it also affects heterosexual men. Despite the perceived stigma, some high profile male celebrities have publicised their struggles with eating disorders such as actor Dennis Quaid, who struggled with what he called "manorexia" for which he sought treatment. Quaid said his problems began when he went on a diet to lose forty pounds to play Doc Holliday in the movie "Wyatt Earp" in 1994. Billy Bob Thornton has also struggled with anorexia, once losing 59 lbs.Thomas Holbrook, M.D., is Clinical Director of the Eating Disorders Program at Rogers Memorial Hospital in Oconomowoc, Wisconsin despite being a psychiatrist specializing in eating disorders, he suffered from anorexia nervosa with compulsive exercising. At one time the 6-ft.-tall psychiatrist weighed just 135 lbs. "I was terrified," he says, "of being fat." His story has been chronicled in various publications including USA Today and People Magazine.