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Risk factors for bulimia nervosa: A controlled study of parental psychiatric illness and divorce
Addictive
Pergamon
Behaviors, Vol. 19. No. 6. pp. 667-675. 1994 Copyright 0 1994 Elsevier Science Ltd Printed in the USA. All rights reserved
0306-4603194 $6.00 + .Ml
0306-4603(94)E0052-M
RISK FACTORS FOR BULIMIA NERVOSA: A CONTROLLED STUDY OF PARENTAL PSYCHIATRIC ILLNESS AND DIVORCE CHRISTINE
E. BOUMANN University
and WILLIAM
of Iowa College
R. YATES
of Medicine
Abstract - Twenty five women with normal-weight bulimia nervosa were compared with 25 age- and weight-matched women without bulimia nervosa on measures of parental psychiatric illness. Case and control probands, as well as their parents, completed the Family History Research Diagnostic Criteria (FH-RDC) interview and a battery of self-report instruments. Case probands and controls were divided into two groups based on evidence for parental psychiatric illness. The assignment of parental psychiatric illness was made by (a) a positive parental history of alcoholism or depression from the FH-RDC; or (b) evidence of parental major depression, alcoholism, or personality disorder from the self-report measures. Parental psychiatric illness occurred significantly more frequently for case probands compared to the control probands (64% vs. 24%, odds ratio = 5.6, 95% Cl = 1.7-19.2). Parental psychiatric illness was also associated with parental divorce (Fisher’s exact p = ,023) and a trend toward lower ratings of paternal but not maternal relationship by case probands. This study suggests parental psychiatric illness may be a risk factor for bulimia nervosa and may contribute to environmental effects through increased rates of divorce and impaired paternal relationships.
Bulimia nervosa, a psychiatric disorder of unknown etiology, is characterized by uncontrolled binge eating episodes in combination with drastic methods of weight control including self-induced vomiting, use of diet pills and laxatives, rigorous exercise, and periodic fasts. Various studies estimate that 1% to 4% of American women are affected with the disorder (Fairburn & Beglin, 1990; Pope, Champoux, & Hudson. 1987; Schotte & Stunkard, 1987: Thelen, McLaughlin, Pruitt, & Smith, 1987). The majority of individuals afflicted with bulimia nervosa are female. Studies investigating two university populations have found 89.5% of those displaying symptoms of bulimia nervosa to be female and 10.5% male (Halmi, Falk, & Schwartz, 1981; Stangler & Printz, 1980). As the awareness, interest, and understanding of the symptomatology and treatment of bulimia nervosa has increased, research has shifted towards the identification of risk factors or markers for individuals who may later develop bulimia nervosa. Family studies have been useful for examining the relationship of bulimia nervosa to major affective disorders and other psychiatric disorders. A series of family studies of psychiatric illness have been completed in bulimia nervosa (Carney, Yates & Cizadlo, 1990; Hudson, Pope, Jonas, & Yurgelun-Todd, 1983; Kasset et al., 1989; Hudson, Pope, Jonas, Yurgelan-Todd, & Frankenburg, 1987; Keck et al., 1990; Logue, Crowe, & Bean, 1989; Stern et al., 1984). The majority of family studies of bulimia nervosa have found increased risk of psychopathology among relatives of case probands compared to control probands. This risk has been primarily linked to major depressive disorder. However, the increased rate of familial psychopathology has not been universally noted (Stern et al., 1984). This research was completed in the Department of Psychiatry, University Iowa City, IA 52242 and was supported by a departmental research grant. Requests for reprints should be sent to William R. Yates, MD, Psychiatry Hawkins Drive #2887 JPP, lowa City, IA 52242.1057. 667
of Iowa College Administration,
of Medicine, UIHC,
200
668
C. E. BOUMANN
and W. R. YATES
Twin studies provide an additional strategy to evaluate genetic and environmental effects for specific psychiatric disorders. Walters et al., (1992) examined the link between major depression and bulimia nervosa in 1,033 twin pairs. This study found common genetic factors contributing to both disorders but some unique genetic and environmental risk factors for each condition. A recent large twin study examined the role of genetic and environmental factors in bulimia nervosa (Kendler et al., 1991). The best-fitting inheritance model suggested familial aggregation was due soley to genetic factors with a heritability of 55%. Other risk factors identified included birth after 1960, low paternal care, a history of wide weight fluctuation, dieting or frequent exercise, a slim ideal body image, low self-esteem, an external locus of control, and high levels of neuroticism. Strober (1991) reviewed the family and genetic studies of eating disorders. Current evidence supports familial aggregration of both anorexia nervosa and bulimia nervosa. Inherited personality traits may increase vulnerability to eating disorders. The significance and role of the family environment in the etiology of bulimia nervosa are less clear. Subjects with bulimia have reported poor marital relationships between their parents as well as poor relationship with their parents (Dolan. Lieberman, Evans, & Lacey, 1990). Increased rates of early parental loss or divorce in families with eating-disordered probands has been found in one family study (Logue et al., 1989). Other studies have been unable to consistently link family environmental findings in bulimia nervosa. Palmer, Oppenheimer, and Marshall (1988) found the familial interactions and relationships so widely varied in families with an individual with bulimia that no significant commonalities existed among them. To further study the role of parental psychiatric illness in bulimia nervosa, we conducted a controlled family study. We limited the family study to parents to case probands to allow for evaluation of possible interactions between familial psychopathology, divorce, and parental relationships. We hypothesized that parental psychiatric illness is a risk factor for bulimia nervosa. We also hypothesized that parental psychiatric illness will be associated with disturbed family relationships and increased severity of bulimia in the proband members. METHODS
The methods for this study have been previously described (Carney, Yates, & Cizaldo, 1990; Yates, 1992). Briefly, 25 women ranging in age from 18 to 43 and meeting DSM-III-R criteria for bulimia nervosa were identified. Subjects had no current or previous history for anorexia nervosa, and were of normal weight (85 130% for height). Cases were recruited through the University of Iowa Hospitals and Clinics Eating Disorders Clinic and through an advertisement for a family study of bulimia nervosa. The case probands were age- and weight-matched with a control group of 25 women without bulimia nervosa also recruited through advertisement.
Proband lifetime history of psychiatric disorders was obtained by administration of the Structured Clinical Interview for Diagnosis (SCID) (Spitzer & Williams, 1987). Probands also completed a battery of self-report instruments including the Eating Disorders Inventory (EDI; (Garner, Olmsted. & Polivy, 1983), the Beck Depression
Parental
risk factors
in bulimia
669
Inventory (BDI; (Beck, 1975), the Brief Michigan Alcohol Screening Test (MAST; (Selzer, 1971), the Personality Disorder Questionnaire-Revised (PDQ-R: (Hyler, Skodol, Kellman, Oldham, & Rosnick, 1990), the Binge Scale (Hawkins & Clement, 1980) and the Restraint Scale (Herman & Po!ivy, 1980; Lowe, 1984). The Diagnostic Survey for Eating Disorders-Revised (DSED-R) was completed by each case proband (Johnson, 1985). This instrument includes a quality-of-relationship rating for relationships with parents. Case probands rated the quality of their relationships with each parent as part of the Life Adjustment Rating Scale. This scale uses a single Likert rating for each parent. Subjects are asked to circle the response that identifies the quality of their relationship with various family members and friends. Quality rating anchor points are identified in the following manner: 1 = terrible, 2 = poor, 3 = fair, 4 = good, 5 = excellent. The control group was asked to complete a packet of self-report instruments which included the lifetime version of the Instrument to Diagnose Depression (IDD-L; (Zimmerman & Coryell, 1988), the Dieting and Eating Behavior Questionnaire, Binge Scale, Restraint Scale, the PDQ-R, and the EDI. The Instrument to Diagnose Depression is an instrument that identifies DSM-III-R (American Psychiatric Association, 1987) criteria for major depression. Current and lifetime diagnoses of major depression can be made with this instrument. Case and control probands also completed the family psychiatric history interview known as the Family History Research Diagnostic Criteria (FH-RDC; (Endicott. Andreasen, & Spitzer, 1978; Zimmerman, Coryell, Pfohl, & Stangl, 1988). This instrument (FH-RDC) generates specific criteria to aid in diagnosing family members for psychiatric illness. For example, the following criteria are needed to positively identify a family member for alcoholism (both A and B are required): A. A problem with drinking not limited to an isolated incident. B. At least one alcohol-related problem in the following areas: 1. Legal, i.e., public intoxication, driving while intoxicated, 2. medical, i.e., cirrhosis, delirium tremens, 3. marital or family problems, 4. occupational, 5. received treatment for alcoholism, 6. social problems, i.e., fighting or losing friends. Family member intervie~~~lassessmc~t~t Attempts were made to contact one parent for each proband by phone. Case and control parents contacted by phone were told they had been identified to participate in a study of diet, mood, and behavior. Parents were not told of the study focus on bulimia nervosa or routinely told they were identified based on their daughter’s participation. Contact parents were interviewed about family history of psychiatric illness using the FH-RDC interview. Both parents received a packet of self-report questionnaires including the PDQ-R, IDD-L, MAST, and Dieting and Eating Behavior Questionnaire. Family members failing to return questionnaires were sent second packets to encourage compliance. The overall return rates for family members of cases and controls were similar (60.8% vs. 60.4%). Direct information via the phone interview or by self-report instruments was available for 37 of 49 mothers and 27 of 47 fathers. When family history information was combined with phone and self-
670
C. E. BOUMANN
and W. R. YATES
report measures, a total of 94% of the case family parents and 98% of the control family parents could be rated for presence of psychiatric illness. All probands and controls were divided into two groups: those with evidence of parental psychiatric illness and those without evidence of parental psychiatric illness. Parents of case subjects and control subjects were defined as having a psychiatric illness in the event of any of the following: (I) Research diagnostic criteria for lifetime alcoholism or depression obtained from either the proband family history interview or parental phone interview (2) lifetime DSM-IIIR criteria for major depressive disorder from the self-report Instrument to Diagnose Depression, (3) a selfreport MAST score of greater than 5 for lifetime alcoholism (4) current evidence of any DSM-IIIR personality disorder as determined from the PDQ-R. The PDQ-R requires self-report of individual DSM-III-R personality disorder criteria as well as self-report of impairment and distress related to the personality disorder.
Statisticrrl
analysis
Two group comparisons were made between: (1) case and control probands. (2) case probands with parental psychiatric illness and case probands without parental psychiatric illness. Statistics tests included unpaired t-tests for continuous measures, calculation of odds ratios, 95% confidence intervals, and Fisher’s Exact test for categorical comparisons. The 95% confidence interval for odds ratios can be used as a test of statistical significance. An odds ratio estimate is considered significant when the lower 95% confidence figure exceeds one. A probability level of alpha = .05 was chosen to indicate statistical significance. A probability level of between .05 and .I0 was considered evidence of a statistical trend.
R E S U I. T S
Table I outlines the information (obtained from the self-report instruments and the FH-RDC) used to classify the parents with psychiatric illness. Significantly more case probands were defined with parental psychiatric illness than control probands. Sixteen individuals (64%) in the case proband group were classified with at least one parent with psychiatric illness, while only six control probands (24%) had at least one parent with psychiatric illness (odds ratio = 5.6, 95% confidence interval = 1.7 to 19.2). Table 2 presents the rates of parental psychiatric illness for parents of case and control probands. Twenty two of fifty case parents met criteria for at least one psychiatric disorder compared to only seven control parents. Both major depression and personality disorder were found significantly more frequently in the parents of probands with bulimia nervosa. Ten percent of the case parents were rated as having alcoholism compared to 4% of the control parents. This difference was not statistically significant. Parental divorce was noted in 28% of the families of case probands compared to 5% of the families of control probands (odds ratio = 9.3, 95% Cl = I. I 82.8). Unpaired t-tests were used to evaluate the differences between case probands with and without parental psychiatric illness on the Binge Scale, Restraint Scale, Eating Disorder Inventory Subscales, Life Adjustment Ratings, Total PDQ-R scores, Beck
ID
25 21 18 22 23 30
20 20 21 19 43 21 20 I8 25 26 21 22 36 23 23 25
psychiatric
-
FH-RDCIIDD
IDD
IDD
Depression
+
_ _
i _
+
+
IDD
FH-RDC
B
FH-RDC FH-RDCIMAST
FH-RDC
FH-RDC
PDQ-R
PDQ-R
PDQ-R
IDD
FH-RDC FH-RDCIIDD
FH-RDCIIDD
IDD IDD FH-RDCIIDD FH-RDC
IDD
PDQ-R
PDQ-R
Personality
illness for case and control
+ _ FH-RDC
FH-RDCIMAST
Alcohol
Father
of parental
FH-RDC
IDD
IDD IDD
Depression
identification
+
+
_
+ _
Parental divorce
I. Instrument
IDD = Diagnosis made from Instrument to Diagnose Depression. FH-RDC = Diagnosis made from Family History-Research Diagnostic Criteria. MAST = Diagnosis made from Michigan Alcoholism Screening Test. PDQ-R = Diagnosis made from Personality Diagnosis Questionnaire-Revised. a Father commited suicide prior to study.
Bulimia 1 2 3 4 9 II 12 13 14 I.5 16 18 I9 22 24 25 Control I 2 IO II I7 24
Family
Proband age
Table
-
FH-RDC
Alcohol
Mother
families
PDQ-R
PDQ-R
PDQ-R
PDQ-R
PDQ-R
PDQ-R
Personality
672
C. E. BOUMANN
Table
2. Rates
of parental
Bulimic
based
on 29 bulimic
psychiatric
parents
and 34 control
illness and divorce
Control
44% 28% 28% 10% 28%
Any psychiatric disorder Major depression Personality disorder” Alcoholism Divorce a Rates
parents
and W. R. YATES
parents
Odds
4.8 3.5 6. I 2.7 4.9
14% 10% 6% 4% 4% parents
completing
ratio
95% Cl (1.8-12.8) (1.2-10.6) ( I .?-32.6) (514.5) (1.1-42.8)
PDQ-R.
Depression scores, and MAST scores. In general, case probands with parental psychiatric illness scored higher than those without psychiatric illness when differences were found. Restraint scale scores were significantly higher for case probands with parental illness (8.9 vs. 5.8, t = 2.79, p = .Oll). Case probands with parental psychiatric illness also showed a trend toward higher scores on the Binge scale (14.9 vs. 11.7, c = 1.80, p = .085) and on the Bulimia subscale of the ED1 (9.0 vs. 5.4, p = .078). There was no evidence of an effect of parental psychiatric illness with measures of current proband psychopathology as measured by the PDQ-R, BDI or MAST scores. Parental psychiatric illness was associated with a trend towared lowered ratings of paternal relationship quality (3.0 vs. 3.9. f = 1.93, p = .068). This relationship appeared to be influenced by a higher rate of divorce among parents with psychiatric illness. Case probands with parental psychiatric illness were more likely to report parental divorce than case probands without parental psychiatric illness (44% vs. O%, Fisher’s Exact p = .023). Parental divorce was associated with lower ratings for the quality of the paternal relationship (divorced = 2.4 vs. nondivorced = 3.7, I = 3.2, p = .005) but not with lower ratings for the quality of the maternal relationship (divorced = 3.7 vs. nondivorced = 3.8, t = ,065, p = .95).
D I S C U S S I 0
N
This study supports parental psychiatric illness as a risk factor for normal-weight bulimia nervosa in women. The existence of parental psychiatric illness may be linked to important family environment variables and may be linked to some psychometric measures used to examine bulimia. Parental psychiatric illness was associated with high rates of divorce in families to probands with bulimia nervosa. Parental psychiatric illness and divorce were also associated with a trend toward lower rating of paternal relationships but not with maternal relationships. Case probands were more likely to have parent with a lifetime history of major depression or a personality disorder. Major depression and personality disorder often occur together in one individual. In this study of parents, personality disorder was assigned in I1 parents of the combined sample. Six of these parents did not have evidence of depression by self-report or family history interview methods. In a previous dimensional personality study of personality in bulimia nervosa, we found that only histrionic and obsessional traits were elevated in parents of probands with bulimia nervosa. However, using a categorical diagnosis of personality in this analy-
Parental
risk factors
in bulimia
673
sis, a significant odds ratio for any personality disorder in parents of probands with bulimia nervosa was found. Future family studies of bulimia nervosa should include an assessment of personality in addition to measures of mood disorders. Few studies of divorce rates in parents of individuals with bulimia nervosa exist. Dolan et al. (1990) found a insignificant divorce rate difference in a study of 50 probands with bulimia nervosa. The rate estimate for divorce in the Dolan case sample was 12% compared to a control rate of 7.5%. However, our divorce rate estimates in this sample are very similar to the rates found in study of 30 probands with either anorexia nervosa or bulimia nervosa (Logue et al., 1989). This study found a rate of combined early parental loss or divorce of 30% for eating disorder probands compared to 5% for normal controls. When we add the early suicide death of one case proband father, our rate of combined early parental loss through death or divorce is 32% for the case group compared to 4% for the control group. The divorce rate in our control group seems small compared to national divorce rates but is consistent with rates in Dolan et al. (1990) and Logue et al., (1989) studies of divorce in control groups. Case probands reported lower quality of relationships with their fathers. Previous work has suggested a role for disturbed maternal relationships in the vulnerability for eating disorders (Strober & Humphrey, 1987). We found no difference in ratings of maternal relationship quality in case probands compared to control probands. Our findings are consistent with the large twin study of Kendler et al. (1991). No maternal-child relationship abnormalites were noted in the Kendler study. Interestingly, Kendler did find low ratings of paternal care from the Parental Bonding Instrument (Parker, 1979) in probands with bulimia nervosa consistent with our finding of lower paternal quality of relationship ratings. Disturbed interpersonal relationships with males other than fathers has also been correlated with symptoms of bulimia in a female college sample (Thelen, Kanakis, & Farmer, 1993). Several limitations in the current study are important to note. The proband and parent sample size is relatively small. Small sample sizes can result in limited power to detect true differences in rates between cases and controls. Additionally, small sample sizes are vulnerable to other methodological confounds in recruitment and assessment. Using a clinical sample supplemented by recruitment by advertisement produces a risk of recruitment bias in our sample. Multiple statistical comparisons can increase the likelihood of a Type I statistical error (identifying a statistical finding by chance rather than true association). Indirect measures of assessment such as self-report and family history methods are inferior to direct interview assessment of all members in a family study. However, the instruments and methods used in the current study, except for the Life Adjustments Rating Scale, do have evidence of reliability and validity. Indirect methods do have the advantage of lower costs and fewer problems with interrater reliability issues. One additional limitation of the family study method of familial risk factors is the inability to determine the cause and effect relationship of identified risk factors. We were unable to assess the chronology of important identified variables. It is possible that identified psychiatric illnesses resulted from parental divorce rather than contributing to parental divorce. It is also possible that some psychiatric symptoms noted in parents are a response to the distress produced by having a daughter with bulimia. Retrospective family studies are limited in determining causal effects. Despite these limitations, our study supports a role for parental psychiatric illness
674
C. E. BOUMANN
and W. R. YATES
in the vulnerability to bulimia nervosa. This vulnerability may be carried through both a genetic and an environmental mechanism. Family history factors need attention in the clinical assessment of patients with bulimia nervosa. The effect of parental divorce on patients with bulimia nervosa should be ascertained. Quality of relationships with parents should be evaluated for women with bulimia, in the clinical setting. These environmental factors may be clinically important in understanding the pathway to bulimia and providing guidelines for important issues in psychotherapy treatment.
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Schotte, D. E.. & Stunkard, A. J. (1987). Bulimia vs bulimic behaviors on a college campus. Journul of rhr American Medical Association, 258, 1213-1215. Seizer, M. L. (1971). The Michigan Alcohol Screening Test: The quest for a new diagnostic instrument. Americun Journal ofPsgchiatrq, 127(12). 1653-1658. Spitzer, R. L., &Williams, J. B. W. (1987). Structured clinical interview for DSM-III-R (4/l/87 version). New York: New York Biometrics Research Department, New York State Psychiatric Institute. Stangler, R. S., & Printz. A. M. (1980). DSM-III: Psychiatric diagnosis in a university population. American Journal of Psychiatry, 137, 937-940. Stern, L. S.. Dixon, N.. Nemzer, E.. Lake, M. D., Sanaone, R. A.. Smeltzer, D. J.. Lantz. S.. & Schrier. S. (1984). Affective disorder in the families of women with normal weight bulimia. Americun Jo~rrtul ofPsychiatry. 141, 1224-1227. Strober. M. (1991). Family-genetic studies of eating disorders. Jorrr-mr/ of Clinicul P.syc,hiarry. 52, lO(Suppl.). 9-12. Strober M., & Humphrey L. L. (1987). Familial contributions to the etiology and course of anorexia nervosa and bulimia. Joumcrl of Consulting und Clinical Psyc~hology, 55. 654-659. Thelen, M. H., Kanakis, D. M. Farmer, J. (1993). Bulimia and interpersonal relationships: An extension of a longitudinal study. Addicfiue Behuuior~. 18. 145-150. Thelen, M. H.. McLaughlin, L., Pruitt, J.. & Smith, M. (1987). Bulimia: prevalence and component factors in college women. Journal ofPsychosomufic Research, 31, 73-78. Walters, E. E., Neale. M. C.. Eaves, 1,. J., Heath, A. C., Kessler, R. C., 81 Kendler, K. S. (1992). Bulimia nervosa and major depression: A study of common genetic and environmental factors. Psychological Medicine. 22, 617-622. Yates, W. R. (1992). Weight factors in normal weight bulimia nervosa: A controlled family study. Internationul Jo~trnul ofEufing Disorders. 11, 227-234. Zimmerman, M., & Coryell, W. (1988). The validity of a self-report questionnaire for diagnosing major depression. Archives of‘Generu/ Psychiutry. 45, 738-741. Zimmerman, M. Coryell. W.. Pfohl. B., & Stangl, D. (1988). The reliability of the family history method for psychiatric diagnosis. Archives of Generul Psychiatry. 45. 320-327.
Pergamon
Behaviors, Vol. 19. No. 6. pp. 667-675. 1994 Copyright 0 1994 Elsevier Science Ltd Printed in the USA. All rights reserved
0306-4603194 $6.00 + .Ml
0306-4603(94)E0052-M
RISK FACTORS FOR BULIMIA NERVOSA: A CONTROLLED STUDY OF PARENTAL PSYCHIATRIC ILLNESS AND DIVORCE CHRISTINE
E. BOUMANN University
and WILLIAM
of Iowa College
R. YATES
of Medicine
Abstract - Twenty five women with normal-weight bulimia nervosa were compared with 25 age- and weight-matched women without bulimia nervosa on measures of parental psychiatric illness. Case and control probands, as well as their parents, completed the Family History Research Diagnostic Criteria (FH-RDC) interview and a battery of self-report instruments. Case probands and controls were divided into two groups based on evidence for parental psychiatric illness. The assignment of parental psychiatric illness was made by (a) a positive parental history of alcoholism or depression from the FH-RDC; or (b) evidence of parental major depression, alcoholism, or personality disorder from the self-report measures. Parental psychiatric illness occurred significantly more frequently for case probands compared to the control probands (64% vs. 24%, odds ratio = 5.6, 95% Cl = 1.7-19.2). Parental psychiatric illness was also associated with parental divorce (Fisher’s exact p = ,023) and a trend toward lower ratings of paternal but not maternal relationship by case probands. This study suggests parental psychiatric illness may be a risk factor for bulimia nervosa and may contribute to environmental effects through increased rates of divorce and impaired paternal relationships.
Bulimia nervosa, a psychiatric disorder of unknown etiology, is characterized by uncontrolled binge eating episodes in combination with drastic methods of weight control including self-induced vomiting, use of diet pills and laxatives, rigorous exercise, and periodic fasts. Various studies estimate that 1% to 4% of American women are affected with the disorder (Fairburn & Beglin, 1990; Pope, Champoux, & Hudson. 1987; Schotte & Stunkard, 1987: Thelen, McLaughlin, Pruitt, & Smith, 1987). The majority of individuals afflicted with bulimia nervosa are female. Studies investigating two university populations have found 89.5% of those displaying symptoms of bulimia nervosa to be female and 10.5% male (Halmi, Falk, & Schwartz, 1981; Stangler & Printz, 1980). As the awareness, interest, and understanding of the symptomatology and treatment of bulimia nervosa has increased, research has shifted towards the identification of risk factors or markers for individuals who may later develop bulimia nervosa. Family studies have been useful for examining the relationship of bulimia nervosa to major affective disorders and other psychiatric disorders. A series of family studies of psychiatric illness have been completed in bulimia nervosa (Carney, Yates & Cizadlo, 1990; Hudson, Pope, Jonas, & Yurgelun-Todd, 1983; Kasset et al., 1989; Hudson, Pope, Jonas, Yurgelan-Todd, & Frankenburg, 1987; Keck et al., 1990; Logue, Crowe, & Bean, 1989; Stern et al., 1984). The majority of family studies of bulimia nervosa have found increased risk of psychopathology among relatives of case probands compared to control probands. This risk has been primarily linked to major depressive disorder. However, the increased rate of familial psychopathology has not been universally noted (Stern et al., 1984). This research was completed in the Department of Psychiatry, University Iowa City, IA 52242 and was supported by a departmental research grant. Requests for reprints should be sent to William R. Yates, MD, Psychiatry Hawkins Drive #2887 JPP, lowa City, IA 52242.1057. 667
of Iowa College Administration,
of Medicine, UIHC,
200
668
C. E. BOUMANN
and W. R. YATES
Twin studies provide an additional strategy to evaluate genetic and environmental effects for specific psychiatric disorders. Walters et al., (1992) examined the link between major depression and bulimia nervosa in 1,033 twin pairs. This study found common genetic factors contributing to both disorders but some unique genetic and environmental risk factors for each condition. A recent large twin study examined the role of genetic and environmental factors in bulimia nervosa (Kendler et al., 1991). The best-fitting inheritance model suggested familial aggregation was due soley to genetic factors with a heritability of 55%. Other risk factors identified included birth after 1960, low paternal care, a history of wide weight fluctuation, dieting or frequent exercise, a slim ideal body image, low self-esteem, an external locus of control, and high levels of neuroticism. Strober (1991) reviewed the family and genetic studies of eating disorders. Current evidence supports familial aggregration of both anorexia nervosa and bulimia nervosa. Inherited personality traits may increase vulnerability to eating disorders. The significance and role of the family environment in the etiology of bulimia nervosa are less clear. Subjects with bulimia have reported poor marital relationships between their parents as well as poor relationship with their parents (Dolan. Lieberman, Evans, & Lacey, 1990). Increased rates of early parental loss or divorce in families with eating-disordered probands has been found in one family study (Logue et al., 1989). Other studies have been unable to consistently link family environmental findings in bulimia nervosa. Palmer, Oppenheimer, and Marshall (1988) found the familial interactions and relationships so widely varied in families with an individual with bulimia that no significant commonalities existed among them. To further study the role of parental psychiatric illness in bulimia nervosa, we conducted a controlled family study. We limited the family study to parents to case probands to allow for evaluation of possible interactions between familial psychopathology, divorce, and parental relationships. We hypothesized that parental psychiatric illness is a risk factor for bulimia nervosa. We also hypothesized that parental psychiatric illness will be associated with disturbed family relationships and increased severity of bulimia in the proband members. METHODS
The methods for this study have been previously described (Carney, Yates, & Cizaldo, 1990; Yates, 1992). Briefly, 25 women ranging in age from 18 to 43 and meeting DSM-III-R criteria for bulimia nervosa were identified. Subjects had no current or previous history for anorexia nervosa, and were of normal weight (85 130% for height). Cases were recruited through the University of Iowa Hospitals and Clinics Eating Disorders Clinic and through an advertisement for a family study of bulimia nervosa. The case probands were age- and weight-matched with a control group of 25 women without bulimia nervosa also recruited through advertisement.
Proband lifetime history of psychiatric disorders was obtained by administration of the Structured Clinical Interview for Diagnosis (SCID) (Spitzer & Williams, 1987). Probands also completed a battery of self-report instruments including the Eating Disorders Inventory (EDI; (Garner, Olmsted. & Polivy, 1983), the Beck Depression
Parental
risk factors
in bulimia
669
Inventory (BDI; (Beck, 1975), the Brief Michigan Alcohol Screening Test (MAST; (Selzer, 1971), the Personality Disorder Questionnaire-Revised (PDQ-R: (Hyler, Skodol, Kellman, Oldham, & Rosnick, 1990), the Binge Scale (Hawkins & Clement, 1980) and the Restraint Scale (Herman & Po!ivy, 1980; Lowe, 1984). The Diagnostic Survey for Eating Disorders-Revised (DSED-R) was completed by each case proband (Johnson, 1985). This instrument includes a quality-of-relationship rating for relationships with parents. Case probands rated the quality of their relationships with each parent as part of the Life Adjustment Rating Scale. This scale uses a single Likert rating for each parent. Subjects are asked to circle the response that identifies the quality of their relationship with various family members and friends. Quality rating anchor points are identified in the following manner: 1 = terrible, 2 = poor, 3 = fair, 4 = good, 5 = excellent. The control group was asked to complete a packet of self-report instruments which included the lifetime version of the Instrument to Diagnose Depression (IDD-L; (Zimmerman & Coryell, 1988), the Dieting and Eating Behavior Questionnaire, Binge Scale, Restraint Scale, the PDQ-R, and the EDI. The Instrument to Diagnose Depression is an instrument that identifies DSM-III-R (American Psychiatric Association, 1987) criteria for major depression. Current and lifetime diagnoses of major depression can be made with this instrument. Case and control probands also completed the family psychiatric history interview known as the Family History Research Diagnostic Criteria (FH-RDC; (Endicott. Andreasen, & Spitzer, 1978; Zimmerman, Coryell, Pfohl, & Stangl, 1988). This instrument (FH-RDC) generates specific criteria to aid in diagnosing family members for psychiatric illness. For example, the following criteria are needed to positively identify a family member for alcoholism (both A and B are required): A. A problem with drinking not limited to an isolated incident. B. At least one alcohol-related problem in the following areas: 1. Legal, i.e., public intoxication, driving while intoxicated, 2. medical, i.e., cirrhosis, delirium tremens, 3. marital or family problems, 4. occupational, 5. received treatment for alcoholism, 6. social problems, i.e., fighting or losing friends. Family member intervie~~~lassessmc~t~t Attempts were made to contact one parent for each proband by phone. Case and control parents contacted by phone were told they had been identified to participate in a study of diet, mood, and behavior. Parents were not told of the study focus on bulimia nervosa or routinely told they were identified based on their daughter’s participation. Contact parents were interviewed about family history of psychiatric illness using the FH-RDC interview. Both parents received a packet of self-report questionnaires including the PDQ-R, IDD-L, MAST, and Dieting and Eating Behavior Questionnaire. Family members failing to return questionnaires were sent second packets to encourage compliance. The overall return rates for family members of cases and controls were similar (60.8% vs. 60.4%). Direct information via the phone interview or by self-report instruments was available for 37 of 49 mothers and 27 of 47 fathers. When family history information was combined with phone and self-
670
C. E. BOUMANN
and W. R. YATES
report measures, a total of 94% of the case family parents and 98% of the control family parents could be rated for presence of psychiatric illness. All probands and controls were divided into two groups: those with evidence of parental psychiatric illness and those without evidence of parental psychiatric illness. Parents of case subjects and control subjects were defined as having a psychiatric illness in the event of any of the following: (I) Research diagnostic criteria for lifetime alcoholism or depression obtained from either the proband family history interview or parental phone interview (2) lifetime DSM-IIIR criteria for major depressive disorder from the self-report Instrument to Diagnose Depression, (3) a selfreport MAST score of greater than 5 for lifetime alcoholism (4) current evidence of any DSM-IIIR personality disorder as determined from the PDQ-R. The PDQ-R requires self-report of individual DSM-III-R personality disorder criteria as well as self-report of impairment and distress related to the personality disorder.
Statisticrrl
analysis
Two group comparisons were made between: (1) case and control probands. (2) case probands with parental psychiatric illness and case probands without parental psychiatric illness. Statistics tests included unpaired t-tests for continuous measures, calculation of odds ratios, 95% confidence intervals, and Fisher’s Exact test for categorical comparisons. The 95% confidence interval for odds ratios can be used as a test of statistical significance. An odds ratio estimate is considered significant when the lower 95% confidence figure exceeds one. A probability level of alpha = .05 was chosen to indicate statistical significance. A probability level of between .05 and .I0 was considered evidence of a statistical trend.
R E S U I. T S
Table I outlines the information (obtained from the self-report instruments and the FH-RDC) used to classify the parents with psychiatric illness. Significantly more case probands were defined with parental psychiatric illness than control probands. Sixteen individuals (64%) in the case proband group were classified with at least one parent with psychiatric illness, while only six control probands (24%) had at least one parent with psychiatric illness (odds ratio = 5.6, 95% confidence interval = 1.7 to 19.2). Table 2 presents the rates of parental psychiatric illness for parents of case and control probands. Twenty two of fifty case parents met criteria for at least one psychiatric disorder compared to only seven control parents. Both major depression and personality disorder were found significantly more frequently in the parents of probands with bulimia nervosa. Ten percent of the case parents were rated as having alcoholism compared to 4% of the control parents. This difference was not statistically significant. Parental divorce was noted in 28% of the families of case probands compared to 5% of the families of control probands (odds ratio = 9.3, 95% Cl = I. I 82.8). Unpaired t-tests were used to evaluate the differences between case probands with and without parental psychiatric illness on the Binge Scale, Restraint Scale, Eating Disorder Inventory Subscales, Life Adjustment Ratings, Total PDQ-R scores, Beck
ID
25 21 18 22 23 30
20 20 21 19 43 21 20 I8 25 26 21 22 36 23 23 25
psychiatric
-
FH-RDCIIDD
IDD
IDD
Depression
+
_ _
i _
+
+
IDD
FH-RDC
B
FH-RDC FH-RDCIMAST
FH-RDC
FH-RDC
PDQ-R
PDQ-R
PDQ-R
IDD
FH-RDC FH-RDCIIDD
FH-RDCIIDD
IDD IDD FH-RDCIIDD FH-RDC
IDD
PDQ-R
PDQ-R
Personality
illness for case and control
+ _ FH-RDC
FH-RDCIMAST
Alcohol
Father
of parental
FH-RDC
IDD
IDD IDD
Depression
identification
+
+
_
+ _
Parental divorce
I. Instrument
IDD = Diagnosis made from Instrument to Diagnose Depression. FH-RDC = Diagnosis made from Family History-Research Diagnostic Criteria. MAST = Diagnosis made from Michigan Alcoholism Screening Test. PDQ-R = Diagnosis made from Personality Diagnosis Questionnaire-Revised. a Father commited suicide prior to study.
Bulimia 1 2 3 4 9 II 12 13 14 I.5 16 18 I9 22 24 25 Control I 2 IO II I7 24
Family
Proband age
Table
-
FH-RDC
Alcohol
Mother
families
PDQ-R
PDQ-R
PDQ-R
PDQ-R
PDQ-R
PDQ-R
Personality
672
C. E. BOUMANN
Table
2. Rates
of parental
Bulimic
based
on 29 bulimic
psychiatric
parents
and 34 control
illness and divorce
Control
44% 28% 28% 10% 28%
Any psychiatric disorder Major depression Personality disorder” Alcoholism Divorce a Rates
parents
and W. R. YATES
parents
Odds
4.8 3.5 6. I 2.7 4.9
14% 10% 6% 4% 4% parents
completing
ratio
95% Cl (1.8-12.8) (1.2-10.6) ( I .?-32.6) (514.5) (1.1-42.8)
PDQ-R.
Depression scores, and MAST scores. In general, case probands with parental psychiatric illness scored higher than those without psychiatric illness when differences were found. Restraint scale scores were significantly higher for case probands with parental illness (8.9 vs. 5.8, t = 2.79, p = .Oll). Case probands with parental psychiatric illness also showed a trend toward higher scores on the Binge scale (14.9 vs. 11.7, c = 1.80, p = .085) and on the Bulimia subscale of the ED1 (9.0 vs. 5.4, p = .078). There was no evidence of an effect of parental psychiatric illness with measures of current proband psychopathology as measured by the PDQ-R, BDI or MAST scores. Parental psychiatric illness was associated with a trend towared lowered ratings of paternal relationship quality (3.0 vs. 3.9. f = 1.93, p = .068). This relationship appeared to be influenced by a higher rate of divorce among parents with psychiatric illness. Case probands with parental psychiatric illness were more likely to report parental divorce than case probands without parental psychiatric illness (44% vs. O%, Fisher’s Exact p = .023). Parental divorce was associated with lower ratings for the quality of the paternal relationship (divorced = 2.4 vs. nondivorced = 3.7, I = 3.2, p = .005) but not with lower ratings for the quality of the maternal relationship (divorced = 3.7 vs. nondivorced = 3.8, t = ,065, p = .95).
D I S C U S S I 0
N
This study supports parental psychiatric illness as a risk factor for normal-weight bulimia nervosa in women. The existence of parental psychiatric illness may be linked to important family environment variables and may be linked to some psychometric measures used to examine bulimia. Parental psychiatric illness was associated with high rates of divorce in families to probands with bulimia nervosa. Parental psychiatric illness and divorce were also associated with a trend toward lower rating of paternal relationships but not with maternal relationships. Case probands were more likely to have parent with a lifetime history of major depression or a personality disorder. Major depression and personality disorder often occur together in one individual. In this study of parents, personality disorder was assigned in I1 parents of the combined sample. Six of these parents did not have evidence of depression by self-report or family history interview methods. In a previous dimensional personality study of personality in bulimia nervosa, we found that only histrionic and obsessional traits were elevated in parents of probands with bulimia nervosa. However, using a categorical diagnosis of personality in this analy-
Parental
risk factors
in bulimia
673
sis, a significant odds ratio for any personality disorder in parents of probands with bulimia nervosa was found. Future family studies of bulimia nervosa should include an assessment of personality in addition to measures of mood disorders. Few studies of divorce rates in parents of individuals with bulimia nervosa exist. Dolan et al. (1990) found a insignificant divorce rate difference in a study of 50 probands with bulimia nervosa. The rate estimate for divorce in the Dolan case sample was 12% compared to a control rate of 7.5%. However, our divorce rate estimates in this sample are very similar to the rates found in study of 30 probands with either anorexia nervosa or bulimia nervosa (Logue et al., 1989). This study found a rate of combined early parental loss or divorce of 30% for eating disorder probands compared to 5% for normal controls. When we add the early suicide death of one case proband father, our rate of combined early parental loss through death or divorce is 32% for the case group compared to 4% for the control group. The divorce rate in our control group seems small compared to national divorce rates but is consistent with rates in Dolan et al. (1990) and Logue et al., (1989) studies of divorce in control groups. Case probands reported lower quality of relationships with their fathers. Previous work has suggested a role for disturbed maternal relationships in the vulnerability for eating disorders (Strober & Humphrey, 1987). We found no difference in ratings of maternal relationship quality in case probands compared to control probands. Our findings are consistent with the large twin study of Kendler et al. (1991). No maternal-child relationship abnormalites were noted in the Kendler study. Interestingly, Kendler did find low ratings of paternal care from the Parental Bonding Instrument (Parker, 1979) in probands with bulimia nervosa consistent with our finding of lower paternal quality of relationship ratings. Disturbed interpersonal relationships with males other than fathers has also been correlated with symptoms of bulimia in a female college sample (Thelen, Kanakis, & Farmer, 1993). Several limitations in the current study are important to note. The proband and parent sample size is relatively small. Small sample sizes can result in limited power to detect true differences in rates between cases and controls. Additionally, small sample sizes are vulnerable to other methodological confounds in recruitment and assessment. Using a clinical sample supplemented by recruitment by advertisement produces a risk of recruitment bias in our sample. Multiple statistical comparisons can increase the likelihood of a Type I statistical error (identifying a statistical finding by chance rather than true association). Indirect measures of assessment such as self-report and family history methods are inferior to direct interview assessment of all members in a family study. However, the instruments and methods used in the current study, except for the Life Adjustments Rating Scale, do have evidence of reliability and validity. Indirect methods do have the advantage of lower costs and fewer problems with interrater reliability issues. One additional limitation of the family study method of familial risk factors is the inability to determine the cause and effect relationship of identified risk factors. We were unable to assess the chronology of important identified variables. It is possible that identified psychiatric illnesses resulted from parental divorce rather than contributing to parental divorce. It is also possible that some psychiatric symptoms noted in parents are a response to the distress produced by having a daughter with bulimia. Retrospective family studies are limited in determining causal effects. Despite these limitations, our study supports a role for parental psychiatric illness
674
C. E. BOUMANN
and W. R. YATES
in the vulnerability to bulimia nervosa. This vulnerability may be carried through both a genetic and an environmental mechanism. Family history factors need attention in the clinical assessment of patients with bulimia nervosa. The effect of parental divorce on patients with bulimia nervosa should be ascertained. Quality of relationships with parents should be evaluated for women with bulimia, in the clinical setting. These environmental factors may be clinically important in understanding the pathway to bulimia and providing guidelines for important issues in psychotherapy treatment.
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