Eating disorders and memory
Many memory impairments exist as a result from or cause of eating disorders. Eating disorders are characterized by abnormal and disturbed eating patterns that affect the lives of the individuals who worry about their weight to the extreme. These abnormal eating patterns involve either inadequate or excessive food intake, affecting the individual's physical and mental health.
In regard to mental health, individuals with eating disorders appear to have impairments in executive functioning, visual-spatial ability, divided and sustained attention, verbal functioning, learning, and memory. Some memory impairments found in individuals with ED, are due to nutritional deficiencies, as well as various cognitive and attentional biases. Neurobiological differences have been found in individuals with ED compared to healthy individuals, and these differences are reflected in specific memory impairments. There are certain treatments and effects of treatments, aimed at these ED-specific memory impairments. Animal research and areas of future research in relation to ED and memory, are also integral to understanding the effects of ED on memory. There are three particular diagnoses of eating disorders that have been linked to memory impairments: anorexia nervosa, bulimia nervosa, and binge eating disorder.
Memory impairments
Memory biases
Individuals with eating disorders show increased tendencies to direct their attention toward irregular eating-related thought processing and attentional bias compared to non-ED individuals. Studies have suggested a strong link between eating disorders and information processing, such as attention and memory. All types of eating disorders consistently display attentional biases towards disorder-related stimuli specific to their ED. Examples of disorder-related stimuli include food, shape, weight, and size. This heightened attention to disorder-related stimuli leads to higher levels of encoding, consolidation and retrieval of this information, acting as a potential cause for the mental maintenance of the disorder.Individuals with eating disorders display several memory and attentional biases to food, shape, weight and size. Specific memory biases include:
- Directed-forgetting: individuals with eating disorders, particularly anorexia nervosa, display more difficulty in forgetting information or cues related to body, shape, and food than those without eating disorders. This leads to greater availability of such memories, facilitating the maintenance of the eating disorder.
- Schema-related: display maladaptive perceptions of food, shape, weight and self that lead to obsessive attention on and enhanced memory for these items, leading to maintaining the eating disorder thought and eating behaviour. Memories for these items are more easily encoded and retrieved compared to other information. Most of the research in this area has been on individuals with anorexia nervosa. Cued recall tasks, recognition tasks and Stroop task tests are used to study these effects. Some studies have shown contradictory results to ED individuals' heightened attention and enhanced memory, however the difference could be attributed to an anxiety-induced response and avoidance behaviour. This could cause impairments in the individuals' ability to remember the information learned, and suggests that more research needs to be done in this area to better understand the relationship between schema-related biases and ED's.
- Selective memory bias: studies have been done on individuals with bulimia nervosa, suggesting selective memory bias exists for positive and negative weight-related items compared to emotional items. Biases towards food-related items were also found, a common finding in individuals with depression.
Explicit memory
In another study, AN participants were found to have less ability to concentrate in the presence of explicit distractors, as well as to have a conscious cognitive bias towards illness-related words. These explicit biases were associated with a longer duration of the illness. A different study characterized AN patients as having trouble integrating positive and negative experiences and that the length of the illness also affected these symptoms and reinforced these impairments. The results of these studies suggest that there are clear differences in the explicit cognitive processing of stimuli between AN individuals and healthy controls and that the length of the illness can affect the extent of these memory biases.
A different study showed that currently ill AN patients had problems with immediate and delayed verbal recall; these disadvantages were also found in weight-restored AN individuals. There was no difference between healthy controls and AN patients in working memory, just memory function. This study demonstrates that there are not only memory biases found in AN individuals but memory impairments as well.
Autobiographical memory deficits have been found in individuals with AN. One study found that AN patients with a history of sexual abuse had impairments in their autobiographical memory characterized by their increased general memory recall. Another study found that anorexic patients are characterized by an overgeneralization of both positive and negative autobiographical memories, which positively correlates with the duration of the illness. The impairment of both positive and negative memories suggests a general impairment in the access to emotional memories. Therefore anorexic patients are more prone to suppress or control not only negative but also positive affect. One hypothesis suggests that these more general memories are what allow these patients to reduce the impact of a negative event.
In one study, participants were exposed to television commercials that were neutral, food-related or body-related. Recall and recognition tests were carried out to test for an explicit memory bias. When compared to healthy controls, BN patients had less recall and recognition for body-related stimuli. This suggests that BN individuals avoid encoding/processing stimuli related to body image and have a selective memory bias.
Obese individuals with binge eating disorders have been compared with obese controls to see if there are different explicit memory biases between these two groups of people. It was found that both groups showed a bias towards negative words, but individuals with BED retrieved positive words less often. This demonstrates an explicit memory bias in which individuals with BED avoid encoding or pay less attention to positive words and focus their conscious attention almost exclusively on negative words. This is similar to the selective memory bias mentioned above.
Implicit memory
It was once thought that individuals with eating disorders had different implicit memory biases and attitudes towards food, depending on the type of eating disorder. BED was associated with a positive evaluation of food, and anorexia and bulimia were associated with a negative evaluation of food. This turns out not to be the case. There were no implicit differences in affective attitudes towards foods between high and low-restraint eaters. This suggests that regardless of the type of eating disorder, individuals with eating disorders view food in similar ways and attitudes towards food.Focusing on obesity, it has been found that obese individuals have more negative attitudes towards high-fat foods than a normal weight control group. It has also been found that children, particularly obese children, were faster at pushing a positive key than a negative key for food. These different attitudes towards food at different ages could represent different stages in the development of obesity. Future research could be done to explore these effects found in obesity and determine if similar effects are seen in individuals with binge eating disorder and perhaps also in individuals with anorexia and bulimia.
Other
A study on the effects of priming combined event-related potential and behavioural reactions, and investigated explicit and implicit associations between shape, weight, and self-evaluations. This was done by means of shape/weight related priming sentences and target words. ERP, reaction times, and subject ratings were collected and priming effects were analyzed. Results showed that there were stronger affective priming effects in patients with AN and BN compared to healthy controls, showing that eating disorder patients associate shape/weight concerns not only with appearance, but also nonappearance-related self-evaluation domains of interpersonal relationships and also with achievement and performance.Social cognition is the understanding and action in interpersonal situations, and include cognitive processes involved in how people perceive and interpret information about themselves, others, and social situations. The dysfunction of social control may play a role in eating disorders. Women with ED have been shown to have lower levels of negative affect attribution compared to healthy controls, which suggests that they learn to expect others to be unavailable and insensitive to their needs. In addition, these patients were less successful at correctly encoding cause-effect relations in a social contexts and it has been suggested that their capacity to mentalize experiences is impaired. In addition to impairments in social cognition, it has been found that individuals with ED have an inability to recognize, label, and respond to different emotional states, and are impaired in visual recognition tasks.
Dementia is a disorder characterized by multiple deficits in cognition, including memory impairments. Patients with various forms of dementia have impairments in their activities of daily living including eating, and eating disorders have been found in patients with dementia. Patients with frontotemporal dementia tend to have an eating disorder where they have food cravings and difficulty controlling the amount and type of food eaten but their memory and spatial functioning is not affected. Meanwhile, patients with Alzheimer's disease, do not have this impairment, but their memory and spatial loss is negatively affected. Similar findings were shown where patients with fronto variant-frontotemporal dementia show more severe and frequent symptoms of eating disorders than patients with AD. ED in patients with dementia have been tracked back to lesions in the frontal subcortical circuits including the anterior cingulate circuit, and data suggests that ED seem to be distinctive features of behavioural syndromes in groups of patients with fvFTD.