Anorexia nervosa and bulimia nervosa were previously thought to have been caused by socio-cultural factors. Nevertheless, recent studies suggest that these conditions are influenced by genes in particular people. Although it has shown good progress, molecular genetics studies of these conditions are in there initial stages. In this article, you will come across evaluations of families, twins and study of genes at molecular level that proposes that genes have significant influence on eating abnormalities and provide extra areas which future studies can focus.
People with anorexia or bulimia have unusual behaviors, shapes and body weights. Despite being very emaciated, those suffering from anorexia are extremely fearful about gaining weight. Bulimia usually occurs after a period of fasting, when one binge eats uncontrollably and then tries to offset excess calories after overeating. They try to get rid of the surplus calories by forcing themselves to vomit, skipping meals, taking excessive laxative drugs, diuretic drugs or enemas. Extremely low body weight doesn’t indicate bulimia. However, 25% to 30% of bulimia patients have a history of anorexia. Most people with anorexia and bulimia have issues with their weight and bodyshape and suffer from depression and anxiety.
Studies suggest that social, biological and developmental factors influence the causes of these conditions. Nevertheless, the nature of these factors is not clearly understood. The way a certain culture perceives a thin person influences the study of mental disorder of people with these eating conditions. However, they are not likely to be enough to influence the development of these conditions. Although most people who diet are usually found in developed countries, approximately only 0.3 to 0.7 percent of females and 1.7 to 2.5 percent of males in these countries suffer from anorexia and bulimia. Besides, anorexia has been described to have existed since the mid 19th century, thus other factors apart from current culture contribute to the causes of the condition. Furthermore, disorders have similar symptoms and effects on certain genders and affect people at the same specific age, and thus they show the probability of some biological vulnerability. The Western perception of slimness may contribute to abnormal eating behaviors such as dieting, which may eventually lead to an eating disorder.
Recent genetic studies on behaviors indicate that the biological vulnerability might be natural. This article focuses on this recent research and recommends the areas that future studies may cover.
Studies on Families: Family researches give the first data concerning the impact of genes on a condition by determining if it mostly affects people who have biological relations. According to controlled family researches, more relatives of women with bulimia and anorexia have eating disorders than the relatives of women who don’t have the two conditions. The largest and most systematic research indicates that the rate of occurrence of anorexia and bulimia amongst relatives of people with eating disorders has increased by 7 to 12 times. This indicates that both disorders are hereditary. Nevertheless, since close relatives have similar genes and live in the same environment, it is difficult for these studies to distinguish between genetic and environmental impacts on vulnerability. The respective impact of genes and environment can be differentiated by conducting systematic studies on twins.
Twin Studies: Twin studies compare the similar features of a disorder or a characteristic in identical and fraternal twins, thus differentiating between the impact of genes from the influence of the environment. Identical twins share all of their genes similarity from their parents or relatives while fraternal twins share just half of their genes. Therefore, genetic impact is evident due to the correlations of identical twins which are double the correlations of the fraternal twins. Generally, the high correlations in identical twins as compared to fraternal twins are found to be the same in anorexia and bulimia disorders. It is estimated that genetic factors accounts for around 58 to 76 percent variance in anorexia and 54 to 83 percent variance in bulimia. These studies show that these traits are moderately transmitted by hereditary factors but the estimates have wide confidence intervals. The remaining liability variance in both anorexia and bulimia seems to be caused by special environmental factors instead of common environmental factors.
Symptoms for eating disorders also seem to be genetic. Twin studies show that approximately 46 to 72 percent of binge eating, forced vomits, and dieting habits are genetic. Similarly some behaviors such as negative attitude towards one’s body, concerns about eating and weight indicates that they are approximately 32 to 72 genetic. The findings indicate that anorexia, bulimia and behaviors that cause or relate to eating disorders have a notable genetic component.
Differences in Development: In making the above conclusions, it should be noted that the effects of genes seems to be different during the various stages of adolescence. This issue has been evaluated by Minnesota Tin Family in recent to twin studies which compared the impact of genes on eating perceptions and habits of samples of 680 twins who were 11 years old and 602 twins who were 17 years old. The samples were based on a population. Initially, these studies indicated the absence of genetic impact on weight concern scores and general eating disorders in twins aged 11 years. On the other hand, genetic factors could account for a variance of 52 to 57 percent in these perceptions and habits in older twins. Although the effects were not very serious, the studies showed a high genetic influence across the age for scores indicating body discontent. The researchers hypothesized that the findings. The authors speculated that these findings may as a result of active disorder causal genes during adolescence.
During a follow-up research, the 11-year-old twin sample was divided into prepubescent and post-pubertal group to evaluate the influence of adolescence on the genetic aspect of these characteristics and behaviors. According to the findings, the results were same as those that were given by the first research. The variance in general eating disorder and weight concerns scores in prepubescent twins had zero percent influence by genetic factors. However, genetic factors accounted for a variance of 26 to 35 in twins who were grouped as post-pubertal. Despite the small sample size of post-pubertal group sample, the two researches had the same pattern of twin correlations which suggested that adolescence contributed to the earlier noted dramatic differences across ages. The high genetic nature in same-age post-pubertal as compared to same-age pre-pubertal twins is a strong indication of possible increased ability of eating pathology to be transmitted genetically. This activation of genetic transmission is possibly caused by ovarian hormones. Apart from showing the developmental differences in the hereditary impacts, these findings are vital in indicating the possible function of ovarian hormones in the genetic transmission of these conditions.
Data explained in this article has helped in the determining the function of genes in eating pathology development. The most thorough studies have estimates which show that a variance of more than 50 percent in liability to eating abnormalities and abnormal eating behaviors are influenced by additive effects of genes. The rest of the variance seems to be caused by special effects of environment. The increased estimates show that the studies that will indentify the particular genes that account for this huge variance are required Studies on twins and family indicate that various characteristics that are transmitted through by genes and mostly co-occur with anorexia and bulimia may be shared similarly through genes. Developmental twin studies are starting to explain why eating disorders develop so quickly. Further study is needed to support our view of the influence of adolescence in activating the effects of genes on eating disorders.
- People with anorexia or bulimia demonstrate unusual behavior and unhealthy body weight
- Most people with anorexia and bulimia have issues with their weight and body shape and suffer from depression and anxiety
- Recent genetic studies on behaviors indicate that biological vulnerability might be natural