First-degree relatives of those with anorexia have roughly 12 times the risk of developing anorexia. Association studies have been performed, studying 128 different polymorphisms related to 43 genes including genes involved in regulation of eating behavior, motivation and reward mechanics, personality traits and emotion. Consistent associations have been identified for polymorphisms associated with agouti-related peptide, brain derived neurotrophic factor, catechol-o-methyl transferase, SK3 and opioid receptor delta-1. Epigenetic modifications, such as DNA methylation, may contribute to the development or maintenance of anorexia nervosa, though clinical research in this area is in its infancy.A 2019 study found a genetic relationship with mental disorders, such as schizophrenia, obsessive–compulsive disorder, anxiety disorder and depression; and metabolic functioning with a negative correlation with fat mass, type 2 diabetes and leptin.One gene that has been linked to anorexia might be of particular interest. This gene codes for a protein called the estrogen related receptor alpha (ERRalpha). In some tissues, this gene alters the ability of estrogen and estrogen receptors to interact with DNA and change the function of cells. Since estrogen has potent effects upon appetite and feeding, any genetic abnormality in the estrogen signaling pathway could contribute to the symptoms of anorexia and explain why anorexia typically appears in young women just after the onset of puberty. Environmental
Obstetric complications: prenatal and perinatal complications may factor into the development of anorexia nervosa, such as preterm birth, maternal anemia, diabetes mellitus, preeclampsia, placental infarction, and neonatal heart abnormalities.
Cardiac complications can be life-threatening, but the heart muscle generally improves with weight gain, and the heart normalizes in size over weeks to months, with recovery. Atrophy of the heart muscle is a marker of the severity of the disease, and while it is reversible with treatment and refeeding, it is possible that it may cause permanent, microscopic changes to the heart muscle that increase the risk of sudden cardiac death. Individuals with anorexia nervosa may experience chest pain or palpitations; these can be a result of mitral valve prolapse. Mitral valve prolapse occurs because the size of the heart muscle decreases while the tissue of the mitral valve remains the same size. Studies have shown rates of mitral valve prolapse of around 20 percent in those with anorexia nervosa, while the rate in the general population is estimated at 2–4 percent. It has been suggested that there is an association between mitral valve prolapse and sudden cardiac death, but it has not been proven to be causative, either in patients with anorexia nervosa or in the general population. Relapse
Rates of relapse after treatment range from 9–52% with many studies reporting a relapse rate of at least 25%. Relapse occurs in approximately a third of people in hospital, and is greatest in the first six to eighteen months after release from an institution. Epidemiology
Anorexia is estimated to occur in 0.9% to 4.3% of women and 0.2% to 0.3% of men in Western countries at some point in their life.