Session 9: Etiology of Bulimia Nervosa
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Analyse etiologies (in terms of biological,
cognitive and sociocultural factors) of Bulimia
Nervosa
Kendler et al (1991)
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Aim: to investigate risk factors and genetic
inheritance in bulimia nervosa
Procedure:
 Sample of 2,163 female twins
 One of twins in each pair had developed bulimia
 Longitudinal study
 Researchers conducted interviews with twins to see if
other twin would develop bulimia
 Compared to see if concordance rates higher with
monozygotic twins (MZ) than dizygotic twins (DZ)
Kendler et al (1991)
 Results: concordance rates of bulimia with
twins
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MZ Twins
DZ Twins
23%
9%
Results indicate a heritability of 55% but this
leaves 45% for other factors
Evaluation Kendler et al (1991)
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Study was a natural experiment therefore researchers
did not manipulate any extraneous variables and there
was no control condition so it is not possible to
establish cause and effect relationship
Questionnable whether twins are representative of
general population-perhaps some aspect of being a
twin puts people more/less at risk of developing a
disorder
All women so cannot be generalised to men
Study does not take into account environmental factors.
It could be that twins grow up in same environment/are
exposed to same environmental risk factors such as a
dysfunctional environment
Genetic vulnerability may predispose an individual but
other factors may trigger disorder. Very important to
study environmental factors too.
Because of highly secretive nature of bulimia, self
reporting may not be best method of data collection
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Other twin studies also demonstrate higher
concordance rate of bulimia in MZ twins than DZ
twins, but rates vary from 23%-83%
Strober (2000) found that first degree relatives of
women with bulimia are 10 times more likely than
average to develop disoder themselves
These differences in findings could be attributed
to both the method of data collection and varying
definitions of the disorder
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Because of highly secretive nature of disorder self
report has not always led to reliable data
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Its possible that some of these familial links could
be due to some shared aspect of environment
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Serotonin is a neurotransmitter associated with
mood, hunger and sleep
Serotonin appears to play a role in bulimia
Increased serotonin levels stimulate the medial
hypothalamus and decrease food intake
Carraso (2000) found lower levels of serotonin in
bulimic patients
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Smith et al (1990) found that when serotonin
levels were reduced in recovered bulimic
patients, they engaged in cognitive patterns
related to eating disorders, such as feeling fat
Body-image distortion hypothesis (Bruch, 1962)
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Bruch (1962) claimed many patients with eating disorders
suffer from the cognitive delusion that they are
overweight.
Research has demonstrated that many ED sufferers
overestimate their body size
However, these studies have also shown that degree of
distortion varies considerably with contextual factors
including the precise nature of instructions given to
subject
Nonetheless, it appears that at least some reports given by
patients demonstrate that they evaluate their own body
size, they are influenced by emotional appraisal rather
than their perceptual experience
Body-image distortion hypothesis
In a reformulation of body-image distortion
hypothesis, Slade and Brodie (1994) suggest that
those who suffer from an ED are in fact uncertain
about the size and shape of their body, and that
when compelled to make a judgment they err on
the side of reporting an overestimation of their
body size.
Body-image distortion hypothesis
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There seems to be a gender difference in perception of body image
Provides anecdotal support for B.I.D hypothesis as there are also gender
differences in prevalence of bulimia
Fallon and Rozin (1985)
 Aim: To compare gender differences in body image and desired body
shape
Procedure:
 475 US undergraduate of both sexes
 Showed 9 pictures of different body shapes from very thin to very heavy
 Asked participants to indicate:
◦ Body shape most similar to their own
◦ Ideal body shape
◦ Body shape of opposite sex they would be most attracted to
Body-image distortion hypothesis
Fallon and Rozin (1985)
Results:
 Women consistently indicated that their current body shape was
heavier than the most attractive body shape
 Their ideal body shape was much thinner than the one they had
chosen for their own body shape
 Men chose similar figures for all three body shapes
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Researchers concluded that men’s perceptions helped them stay
satisfied with body shape whereas women’s perceptions put
pressure on them to lose weight.
These sex differences could probably be linked to a higher
prevalence of dieting, anorexia and bulimia among US women.
Role of Cognitive Disinhibition
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In addition to perceptual distortions, Polivy and
Herman have looked at the role of cognitive
disinhibition
This occurs because of dichotomous thinking- an all
or nothing approach to judging oneself
Bulimics follow very strict dieting rules in order to
reach the weight that they feel is ideal
When they break their own rules, they tend to binge
eat
Thoughts about eating (cognitions) act to release all
dietry restrictions (disinhibiton)
Role of Cognitive Disinhibition
Polivy and Herman (1985)
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Asked dieters and non-dieters to take part in a
taste test
Before taking part in test, they were given a
chocolate milkshake
After drinking milkshake, they were given 3 types
of ice cream to sample
Told they could eat as much as they liked
Role of Cognitive Disinhibition
Polivy and Herman (1985)
Results
Dieters ate significantly more than non-dieters
Study raises interesting questions: if 3/4
women diet at some point in their lives but
only 1/33 suffer from bulimia, why do we not
see more bulimia?
Weight related schemata model
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Fairburn (1997) suggested people with eating
disorders had distorted weight related schemas
and low self-esteem
Distorted beliefs and attitudes towards body
shape and weight develop partly because of the
high status given to looking thin and attractive
Individuals strive to control body weight to stay
thin and they base self worth on being thin i.e.
they have a weight related self schema that
distorts the way they percieve and interpret their
experiences
Weight related schemata model
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For some people, their concerns and
prioritisation of weight control may reflect a
wider lack of self-esteem and a vulnerability to
cultural messages about body weight
They think they will feel better if they lose weight
but this obsession with weight control may lead
to depression and intensified feelings of low self
esteem because weight control is their main way
of maintaining self worth
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Cognitive explanations of bulimia that
patients suffer from perceptual distortions
and maladaptive cognitive patterns are more
descriptive than explanatory
It does not explain how these distortions
arise in the first place
It is very difficult to establish cause and effect
since disordered eating patterns may result in
distorted thinking rather than vice versa
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Perceptions of the perfect body are influenced by
cultural ideals
In the West, images of the ideal body shape for
women have changed over the years from an
hourglass shape to a slimmer shape.
In the 1950s female sex symbols had much
larger bodies compared with those of the present
day
Celebrities represent an ideal that people
compare themselves to, so they establish
standards for how we should look whether they
intend to or not
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People constantly compare themselves to
other people and their self esteem is affected
by this
Thanks to the media, we have become
accustomed to extremely rigid uniforms of
beauty
Television, billboards and magazines expose
us to “beautiful people” all the time, making
exceptional good looks seem real, normal
and attainable
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Standards of beauty have in fact become
increasingly difficult to attain, particulalry for
women.
The current media ideal of thinness for
women is achieveable by less that 5% of the
female poplulation
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Many eating disorders begin when a young
women who is not substantially overweight
comes to believe that she needs to go on a
diet
Aspects of the woman’s personal history,
biological make-up and thought processes
may contribute to dissatisfaction with body
weight, but the desire to be thin is often
powerfully influenced by media images and
messages
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The media both reflects and helps to shape a
strong cultural pressure towards thinness
The rise in the incidence of eating disorders
which has become evident in recent years
throughout Europe, and in the US and Japan
is frequently attributed to an increase in
cultural emphasis on thinness as an ideal
boyd shape
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The representation of the ideal female as thin is also
apparent in coverage of children’s fashion and in the
design of dolls so even very young girls are subjected
to distorted models of ideal body shape.
Sanders and Bazalgette (1993)
Analysed the body shape of 3 of most popular dolls
available for young girls (Barbie, Sindy and Little
Mermaid)
Measured height, hips, bust and waist.
Then transformed measurements to apply to a real
woman of average height
Relative to real women all dolls had tiny hips and
waists and greatly exagerrated leg lengths
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Distorted ideas about what is normal and
acceptable mean that many women, even
children become dissatisfied with their own
shape even though it is within the healthy
range.
Waddle and Marsland (1990) report that by
the age of 12, body shape can be a major
criterion in self evaluation and the evaluation
of others and that many people have
prejudices against overweight people.
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Men, too are beginning to come under pressure.
The ideal “worked out” male figure that appears
in many commericals produces a strong demand
to mirror the ideal
In 1993, a MORI survey of adult males in UK
found that:
1/3 of men had been on a diet
2/3 of men believed a change in shape would
make them more sexually attractive
It remains to be seen whether the growing
emphasis on an ideal male shape will lead to an
increase in the number of men who suffer from
EDs
Levine et al (1990)
 Aim: to investigate relationship between
sociocultural factors and eating attitudes and
behaviours
Procedure:
 USA, 385 girls aged 10-14 years
 Answered questions about eating behaviour,
body satisfaction, concern with being thin,
parents’ and peers’ attitudes, and magazines
with regard to weight management techniques
and the importance of being thin
Levine et al (1990)
Results
 Majority of respondents said they received clear
messages from fashion magazines, peers and family
members that its important to stay thin
 Also reported the same sources encouraged dieting
or other methods to keep a slender figure
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Study found 2 important factors in drive for thinness
and disturbed patterns of eating:
1.
2.
Reading magazines containing information about ideal body
shapes and weight management
Weight related teasing or criticism from family
Levine et al (1990)
Conclusions
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The results indicate that body dissatisfaction and
weight concerns reflect sociocultural ideals of a
female role and raises the possibility that some
adolescent girls live in a subculture of intense
weight and body image concern that places them
at risk for disordered eating behaviour such as
bulimia nervosa
Jaeger et al (2002)
Aim: to conduct a cross cultural investigation of the
relationship between body dissatisfaction and the
development of bulimia to see if there were cross
cultural differences in vulnerability to bulimia
Procedure:
 Cross cultural sample of 1751 female medical and
nursing students from 12 nations including western
and non-western countries
 This was a natural experiment as the IV (culture)
could not be controlled by experimenter
Jaeger et al (2002)
Procedure:
 Self report method used to obtain data on body
disatisfaction, self esteem and dieting behaviour
 Participants’ BMI (height and weight) was taken
 Participants saw a series of 10 body silhouettes,
designed to be as culture neutral as possible in
order to measure body dissatisfaction
Jaeger et al (2002)
Results
 Significant differences between cultures were found
 Most extreme body dissatisfaction found in
Mediterranean countries followed by northern
European countries
 Countries in process of weternisation showed an
intermediate amount of body dissatisfaction
 Non-western countries showed lowest levels of
dissatisfaction
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Body dissatisfaction was found to be most important
factor in dieting behaviour in most countries
Jaeger et al (2002)
Conclusions
 The significant differences between cultures support
the explanation that bulimia is due to “idealised”
body images portrayed in media which encourage
disorted views and consequently, body dissatisfaction
and dieting.
 Western countries are more exposed to these images
and show higher body dissatisfaction
 Implications are that explanations of disorder must
be considered at a macro-level (society) rather than
origninating solely within individual (micro-level)
Jaeger et al (2002)
Jaeger et al (2002)
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Study was a natural experiment and uses culture as a
variable but it is impossible to establish cause and effect
ere as “culture” is not a controlled variable. Causation
cannot be inferred.
Ignores the role of genetic factors in causing bulimia, even
though heredity certainly plays a part in development of
disorder
It is not easy to separate nature/nuture but it is
oversimplified and reductionist to consider only one
explanation
Participants were all medical or nursing students. Such
reltively well-educaated groups do not form representative
samples and it is not at all clear that other groups in each
country would have similar levels of disatisfaction
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The causes of bulimia appear to be
multifaceted
Research suggests that bulimia develops due
to a complex interaction from a range of
factors including biological, cognitive and
sociocultural