Subjective theories of illness in fibroid and endometriosis patients: Similarities,differences,and influencing factors

Abstract

Introduction:

The aim of this study was to compare the subjective theories of illness in patients with fibroids and patients with endometriosis, and to identify potential factors influencing them.

Methodology:

Participating patients were recruited via three specialized centers for fibroids and endometriosis. To assess their subjective theories concerning the cause of their illness, we used a questionnaire based on the revised Illness Perceptions Questionnaire (IPQ-R). We also gathered and evaluated data relating to sociodemographic factors and psychological distress or possible anxieties using the Kessler Psychological Distress Scale (K10) and the Generalised Anxiety Disorder Assessment (GAD-7).

Results:

We were able to analyze data from 201 patients with fibroids and 212 patients with endometriosis. About 94.4% of the patients had one or more subjective theories concerning the cause of their illness. Both groups perceived “stress or worry” to be the most probable cause of their illness. Compared to endometriosis patients, patients with fibroids were more likely to assume “aging” and “heredity” as the cause of their illness. Endometriosis patients, on the other hand, were more likely to choose theories pertaining to the “environmental influences and immune system” category. The patients’ age, formal education, and conspicuous score values in the K10 or GAD-7 questionnaire proved to be important factors influencing their beliefs about the cause of illness.

Conclusion:

Patients perceive stress and psychological strain as possible causes for their illness. It might be beneficial to take this information into account in conversations between doctors and patients and when drawing up psychosomatic-gynecological treatment plans.

Keywords

Illness perception subjective theories of illness uterine fibroids IPQ-R K10 GAD-7 endometriosis medical treatment

Introduction

According to Leventhal’s “Common-Sense-Model of Illness Representation,” subjective illness theories comprise all personal considerations regarding the identity, cause, consequences, timeline, and controllability of an illness.^1,2 It is believed that most patients form a unique subjective theory of illness during the course of their disease.³ These theories are dynamic concepts and adapt to changes in the patients’ lives and are influenced by personal, sociodemographic as well as illness-specific factors.^4–8 Normally, these theories are not discussed during medical consultations, but during the last decades researchers were able to show that they can have a considerable impact on the health behavior of patients, both positive and negative, especially regarding adherence to therapy.^4,9,10

Previous research on subjective theories of illness in gynecology has mainly focused on malignant diseases.¹¹ Very few studies are available internationally on subjective theories of illness in patients with fibroids or endometriosis, even though, fibroids and endometriosis are the most common benign chronic proliferative illness in gynecology.^12–16 Moreover, Symptoms related to fibroids and endometriosis can have a significant impact on the quality of life of the women affected.^17–20

Consequently, the objective of our own cross-sectional study was to answer two main questions: What kinds of subjective theories of illness do patients with fibroids and patients with endometriosis have? And which sociodemographic factors influence these theories?

Methodology

Study population

From June to December 2017, all first-time patients who visited one of two outpatient clinics specialized in fibroids and endometriosis at Charité-Universitätsmedizin Berlin (M.D. and S.M.) or one selected gynecological practice specialized in endometriosis (A.D.E.) in Berlin were invited to participate in the study. The inclusion criteria were: at least 18 years of age, sonographically detected fibroids or clinically and symptomatically confirmed endometriosis and sufficient knowledge of German or English to answer the questionnaire. Since medical consultations might influence the patients believes about an illness, we only included patients at their first consultation of a specialized doctor in fibroids and endometriosis.⁶ To differentiate between subjective theories of illness in patients with fibroids and endometriosis, women affected by both fibroids and endometriosis were excluded from this study. The number of cases necessary for the study was estimated based on the occurrence of genetic predisposition as suspected cause of illness in patients with fibroids in the study of David et al.¹⁴ since genetic predisposition is a known risk factor for both fibroids and endometriosis that has been verified in literature.^21,22 67.3% of patients in the cohort of David et al.¹⁴ believed a genetic predisposition was the cause of their fibroids. Our hypothesis was that this figure would be lower in patients with endometriosis and therefore allowed for 15% lower prevalence in this group. It was thus estimated that we would need to interview at least 182 women in each the endometriosis and the fibroids group, with a power of 80%. Taking into account an expected drop-out rate of 10%, we determined a final number of 200 patients to be interviewed per group.

Questionnaire set

A German language questionnaire consisting of 69 items was employed to survey the subjective theories of illness. The “cause” section of the revised Illness Perception Questionnaire (IPQ-R) provided the basis for the questionnaire, to which we added the items “fate” and “influence of (a) god,” following Barnes et al.²³ and Moss-Morris et al.²⁴ The patients were asked to assess each item of the IPQ-R relating to possible causes of their illness using a five-point Likert scale (“strongly disagree” to “strongly agree”). The isolated use of only one section of the IPQ-R was endorsed by its originator.

We also recorded numerous factors which are believed to potentially influence the subjective theories of illness, such as various sociodemographic factors, the type of disorder as well as the self-assessed level of knowledge about the illness.^5,6 In addition, we recorded whether patients had an unfulfilled desire to have children in order to investigate possible effects on the subjective theories of illness. The Kessler Psychological Distress Scale questionnaire (K10) and the Generalized Anxiety Disorder 7 questionnaire (GAD-7) were used to identify possible anxiety disorders and other forms of psychological distress that might have an impact on the theories of illness.^25,26

Statistics

We relied on IBM SPSS Statistics version 25 for the statistical evaluation of the questionnaires. We performed an exploratory analysis of the data, determining statistical parameters such as median and interquartile range as well as absolute and relative prevalence. In order to assess the level of agreement for each of the IPQ-R items, we performed a dichotomization: The answers “agree” and “strongly agree” were classified as agreement, the answers “neither agree nor disagree,” “disagree,” and “strongly disagree” were not classified as agreement. For the comparison of the fibroid patients and the endometriosis patients as well as for the comparison of two groups, we used the Mann-Whitney U test for continuous data, Kendall’s tau-b coefficient for ordinal data and Fisher’s exact test for dichotomous data. The statistical significance was set at p < 0.05.

We performed the factor analysis for both groups together and limited the number of factors to four. We then established four scales, which were subjected to reliability analysis for internal consistency. In order to compare the scales and the single items for fibroid and endometriosis patients, we performed a multivariate analysis comprising several confounding variables (age, migration background, formal education, and self-assessed level of knowledge about the illness). Linear regressions were used to calculate the continuous variables (scales). The ordinal single items were dichotomized (see above) and analyzed using logistic regressions.

Ethics and data protection

The study was approved by the ethics committee of the Charité-Universitätsmedizin Berlin (application number: EA4/088/17). The requirements of the Charité for good scientific practice and the Berlin Data Protection Act were both adhered to.

Results

In total, 225 patients with fibroids and 242 patients with endometriosis were invited to participate in the study, 201 fibroid and 212 endometriosis patients completed the questionnaire set (see Figure 1). Drop-out rates were similar at 10.7% for fibroid patients and 12.4% for endometriosis patients (p = 0.567). For a summary of all sociodemographic data, see Table 1.

Figure 1.

Drop-out rate among patients with fibroids and patients with endometriosis.

Table 1.

Sociodemographic characteristics of patients with fibroids and patients with endometriosis.

	Fibroids n = 201	Endometriosis n = 212	p-Value
Median age, in years	42	32	p < 0.001
Migration background, n (%)	72 (35.8)	60 (28.3)	p = 0.114
High school diploma, n (%)	142 (70.6)	147 (69.3)	p = 0.830
Working/studying, n (%)	185 (92.0)	189 (89.2)	p = 0.400
Religious affiliation, n (%)	82 (40.8)	71 (33.5)	p = 0.128

Bold font indicates statistical significance

Causal beliefs of patients with fibroids and endometriosis

About 60.2% of the participants reported having thought about the cause of their illness. Endometriosis patients were less likely to talk about these thoughts with their gynecologist than patients with fibroids (26% vs 39%) (p = 0.039). One in six endometriosis patients, as well as nearly one in eleven fibroid patients indicated that they were uncomfortable expressing their personal thoughts on the cause of illness to their physician (p = 0.127).

About 94.4% of the patients chose at least one of the 20 items of the IPQ-R as a possible cause of their illness. The three most common subjective theories of illness in patients with fibroids were “stress or worry” (58.2%), “aging” (54%), and “hereditary” (46.2%); in endometriosis patients, these were “stress and worry” (64.8%), “chance or bad luck” (51.2%), and “altered immunity” (45.8%) (see Figure 2).

Figure 2.

Patient agreement with the IPQ-R items.

Results of the factor analysis of the IPQ-R items

For the total population of patients, we were able to identify four factors that explained 54% of the variance within the data (see Table 2). “Hereditary” was the only item not clearly assignable to any of the categories. The four categories included: “psychological reasons,” “risk behavior and age,” “environmental influences and immune system,” as well as “force majeure.” The internal consistency of the categories “psychological reasons” and “environmental influences and immune system” was satisfactory (see Table 2). The internal consistency of the “risk behavior and age” category was enhanced by excluding the item “aging” (Cronbach’s α = 0.746).

Table 2.

Factor analysis of the IPQ-R listing the items and their respective factor loading.

	Factor 1	Factor 2	Factor 3	Factor 4
Category 1: “Psychological reasons” (Cronbach’s α = 0.871)
Stress and worries	0.693	−0.096	0.344	0.038
Own behavior	0.505	0.359	0.347	0.148
Own attitude	0.842	0.189	0.010	0.012
Family problems or worries cause fibroids/endometriosis	0.800	0.133	0.103	0.012
Overwork	0.688	0.105	0.274	−0.016
Own emotional state	0.852	0.096	0.176	0.042
Own personality	0.580	0.386	0.012	0.241
Category 2: “Risk behavior and age” (Cronbach’s α = 0.697)
Aging	0.028	0.466	0.239	0.001
Alcohol	0.140	0.746	0.325	−0.102
Smoking	0.179	0.735	0.221	−0.031
Accident or injury	0.138	0.741	0.057	0.085
Category 3: “Environmental influences and immune system” (Cronbach’s α = 0.711)
A germ or virus	0.050	0.137	0.692	0.011
Diet or eating habits	0.335	0.134	0.631	0.025
Poor medical care in the past	0.022	0.252	0.427	0.335
Pollution in the environment	0.240	0.175	0.660	0.159
Altered immunity	0.233	0.245	0.620	−0.102
Category 4: “Force majeure” (Cronbach’s α = 0.541)
Chance or bad luck	0.094	−0.100	0.173	0.662
Influence of (a) god	0.172	0.473	−0.033	0.485
Fate	0.110	0.163	0.155	0.755
No assignment possible
Heredity	0.082	0.077	0.164	−0.349

Bold font marks the greatest item loadings on the respective factor

Patients with endometriosis were more likely to agree to questions belonging to the category “environmental influences and immune system” than patients with fibroids (p = 0.009). Both groups showed the same agreement rate regarding the categories “psychological reasons” (p = 0.361) and “risk behavior” (p = 0.469).

Factors influencing patients’ IPQ-R responses

The results of a multivariate analysis revealed that potential influencing factors such as differences in age, migration background, self-assessed knowledge about the illness, or formal education had no effect on differences between the fibroid and the endometriosis groups. We then analyzed whether these factors had an impact on the responses regardless of the illness. We found that migration background and self-assessed knowledge did not affect the responses of patients in the overall collective. However, older patients were more likely to consider “aging” to be the cause of their illness (tau_b = +0.25; p < 0.001), while younger patients tended to attribute it more to “chance or bad luck” (tau_b = − 0.10; p = 0.010) (see Table 3).

Table 3.

Factors influencing the response behavior of patients in the IPQ-R.

	Age		Migration background		Formal education		“Good” self-assessed knowledge		Unfulfilled desire to have children		Non-specific psychological distress*		Anxiety symptoms**
	tau	p	tau	p	tau	p	tau	p	tau	p	tau	p	tau	p
Scales
Psychological reasons	−0.04	p = 0.324	+0.01	p = 0.735	−0.01	p = 0.971	−0.02	p = 0.679	+0.03	p = 0.420	+0.26	p < 0.001	+0.18	p < 0.001
Risk behavior	+0.01	p = 0.845	−0.05	p = 0.249	+0.06	p = 0.219	−0.07	p = 0.116	−0.02	p = 0.653	+0.04	p = 0.381	−0.01	p = 0.887
Environmental influences and immune system	−0.05	p = 0.160	+0.01	p = 0.796	+0.01	p = 0.739	−0.01	p = 0.758	+0.06	p = 0.172	+0.18	p < 0.001	+0.11	p = 0.009
Single items
Aging	+0.25	p < 0.001	−0.04	p = 0.361	−0.08	p = 0.073	−0.07	p = 0.133	−0.04	p = 0.359	−0.01	p = 0.884	+0.02	p = 0.624
Chance or bad luck	−0.10	p = 0.010	+0.03	p = 0.582	−0.06	p = 0.214	−0.01	p = 0.876	−0.03	p = 0.511	+0.05	p = 0.347	+0.91	p = 0.053
Influence (of a god)	+0.05	p = 0.262	+0.02	p = 0.725	+0.12	p = 0.011	−0.06	p = 0.218	+0.01	p = 0.817	+0.05	p = 0.282	−0.01	p = 0.798
Fate	−0.01	p = 0.747	−0.02	p = 0.723	+0.09	p = 0.070	−0.01	p = 0.916	+0.05	p = 0.339	+0.11	p = 0.024	+0.12	p = 0.010
Hereditary	+0.07	p = 0.052	+0.07	p = 0.146	−0.07	p = 0.122	+0.01	p = 0.898	+0.05	p = 0.265	+0.05	p = 0.270	+0.01	p = 0.890

Non-specific psychological distress: K10 score ⩾25 points.

Anxiety symptoms: GAD-7 score ⩾5 points.

Bold font indicates statistical significance

Patients with a suspected diagnosis of a (moderately) severe mental disorder based on the K10 questionnaire (K10 score ⩾25 points) and patients with anxiety symptoms according to the GAD-7 (GAD-7 score ⩾5 points) were more likely to cite “psychological reasons,” “environmental influences and immune system,” and “fate” as cause of their illness (see Table 3).

Discussion

This is the first study that analyzes subjective theories of illness in patients with endometriosis using a standardized questionnaire and also the first study comparing subjective theories of illness in patients with endometriosis and fibroids. Research groups from various disciplines have successfully compared subjective illness theories for two illnesses with certain similarities, so it seems valid and reasonable to compare subjective illness theories in patients with fibroids and patients with endometriosis, since both are benign chronic proliferative illnesses in gynecology.^27–30

As in other studies concerning patients with tumors, irritable bowel syndrome or fibroids, the proportion of patients who agreed to at least one possible subjective theory of illness when completing a standardized questionnaire such as the IPQ-R was very high (over 90%).^14,31,32

One in six patients with endometriosis and one in eleven patients with fibroids reported feeling uncomfortable sharing personal thoughts about the cause of their illness with their physician. Many patients with endometriosis have experienced a long history of suffering as well as poor communication with physicians, resulting in frequent changes of their physician, which might be holding them back from sharing their subjective theory of illness.^33,34

Among the IPQ-R questionnaire, “stress or worry” was the most commonly assumed cause of illness in both patients with fibroids and patients with endometriosis, while the latter were even more likely to perceive this as the main cause than patients with fibroids. A previous study on subjective theories of illness in fibroid patients also confirmed stress as a frequently mentioned factor.¹⁴ According to the only published study on subjective theories of illness in endometriosis patients to date, one in eight women assumed that the cause of their illness was prioritizing their career.¹⁶ Stress as a cause of illness is receiving more and more attention, and the notion of stress is now thought to be dominant in our culture.^6,7,35,36 It is no surprise that this is also reflected in patients’ subjective theories of illness. Other studies on subjective theories of illness suggest that patients assuming psychosomatic causes tend to suffer from a higher rate of depression, guilt and an increased level of perceived emotional distress.^36,37

Another commonly assumed risk factor in both groups was heredity. On the whole, patients with fibroids were more likely to attribute their illness to heredity than patients with endometriosis. According to current research, genetic factors do play a role in the development of both illnesses: Women with a positive family history of fibroids are three times more likely to develop the illness themselves.²¹ The occurrence of endometriosis in first-degree relatives increases the personal risk of also developing the illness by a factor of 3–9.²² Previous studies on the subjective illness theories of patients with fibroids confirm that patients frequently assumed “hereditary factors” to be the cause of their illness.¹⁴ When patients believe that the cause of their illness cannot be influenced, they tend to worry less about their own (deficient) behavior. Perceiving one’s illness as hereditary can thus have a relieving effect.³⁸

Patients with endometriosis were more likely to agree to questions from the category “environmental influences and immune system” than patients with fibroids. According to current research, it is likely that immunological changes play a role in the development of endometriosis.³⁹ The reason why almost one in two endometriosis patients believed that the immune system was involved in the development of their illness might be due to the fact that this knowledge is spreading among patients. According to a paper on the coverage of endometriosis in the press, endometriosis is frequently associated with autoimmune diseases and environmental pollutants in women’s magazines.⁴⁰ There has been an increase in subjective theories of illness involving environmental, nutritional and immune factors regarding other illnesses as well.^7,36 It is assumed that patients are more likely to choose subjective theories of illness relating to topics that are currently debated in society, such as environmental pollution, the immune system, or a poor diet. This becomes especially apparent when applying a questionnaire to collect data.³⁶

Being aware of the factors that influence patients’ subjective theories of illness is important when identifying groups of patients who are particularly and adversely impacted by certain theories and who might benefit from support in coming to terms with them.⁵

Age

Older patients are more likely to attribute their illness to aging than to chance. Studies relating to other medical conditions have confirmed that older people are more likely to attribute their health problems to age.^41,42

In the first study on subjective theories of illness in patients with fibroids published in 1983, 9% of patients assumed that aging might be the cause of their illness.¹⁵ In our study cohort, more than 50% assumed that there was a correlation.

Migration background

Although results from previous studies suggested that having a migration background might impact one’s subjective theory of illness, our study did not confirm this. According to some studies, patients with migration background were more likely to favor external causal attributions.^14,35,43

Psychological irregularities

Patients with test scores indicative of general psychological distress (K10) or anxiety symptoms (GAD-7) were more likely to assume psychological reasons, environmental factors and disorders of the immune system as well as “fate” as the cause of their illness. A different study on heart failure patients showed that patients with an elevated GAD-7 score favored theories that attributed the cause of their illness to psychological reasons.⁴⁴ It is conceivable that patients who believe that their illness is rooted in their psyche are more likely to blame themselves for their illness and, as a result, develop more anxieties.²⁷ Considering that these patients seem to have difficulties in coping with their illness and tend to feel guilty, they should be offered psychosocial support.^36,37

Strengths and weaknesses of the study

The study presented here is the first cross-sectional study assessing and comparing the subjective theories of illness of patients with fibroids and patients with endometriosis. The rate of patients who refused to participate in the survey was low (11.6%).

We collected the data by means of an established questionnaire (IPQ-R), which is considered to be a rather rigid survey instrument, but which ensures good comparability of the results obtained. The results presented here can only be generalized to a limited extent, as the participants were selected locally in a specialized outpatient clinic or practice.

Footnotes

Authors’ note

Parts of this manuscript are based on the first author’s dissertation.

Authorship

F.M. and M.D. researched literature and conceived the study. A.D.E., S.M., M.D., and F.M. were involved in patient recruitment. R.R. and F.M. were involved in data analysis. F.M. and M.D. wrote the first draft of the manuscript. All authors reviewed and edited the manuscript and approved the final version of the manuscript.

Ethical approval

Ethical approval for this study was obtained from the ethics committee of the Charité-Universitätsmedizin Berlin (application number: EA4/088/17).

Informed consent to participate

Written informed consent was obtained from all participants before the study.

Informed consent to publish

Written informed consent was obtained from the patients for their anonymized information to be published in this article.

Trial registration

DRKS00025093 URL: https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00025093

ORCID iD

Friederike Münch

References

Leventhal

Benyamini

Brownlee

, et al. Perceptions of health and illness: current research and applications. In: KJ

Petrie

Weinman

(eds) Illness representations: theoretical foundations. Amsterdam: Harwood Academic Publishers, 1997, pp.19–46.

Leventhal

Phillips

Burns

. The common-sense model of self-regulation (CSM): a dynamic framework for understanding illness self-management. J Behav Med 2016; 39: 935–946.

Weinman

Petrie

Moss-morris

, et al. The illness perception questionnaire: a new method for assessing the cognitive representation of illness. Psychol Health 1996; 11: 431–445.

Leventhal

Meyer

Nerenz

. The common sense representation of illness danger. In: S

Rachman

(ed.) Contributions to medical psychology. Oxford: Pergamon Press, 1980, pp.7–30.

Aalto

A-M

Heijmans

Weinman

, et al. Illness perceptions in coronary heart disease: sociodemographic, illness-related, and psychosocial correlates. J Psychosom Res 2005; 58: 393–402.

Amann

Wipplinger

. Die Relevanz subjektiver Krankheitstheorien für die Gesundheitsförderung [The relevance of subjective theories of illness for health promotion]. In: G

Amann

Wipplinger

(eds) Gesundheitsförderung - ein multidimensionales Tätigkeitsfeld (Health promotion - a multidimensional field of activity). Tübingen: DGVT-Verlag, 1998, pp.153–175.

Petrie

Weinman

. Why illness perceptions matter. Clin Med 2006; 6: 536–539.

Faltermaier

Kühnlein

Burda-Viering

. Subjektive Gesundheitstheorien: Inhalt, Dynamik und ihre Bedeutung für das Gesundheitshandeln im Alltag [Subjective theories of health: content, dynamics and their importance for health behavior in everyday life]. J Public Health 1998; 6: 309–326.

Kucukarslan

. A review of published studies of patients’ illness perceptions and medication adherence: lessons learned and future directions. Res Soc Adm Pharm 2012; 8: 371–382.

10.

Birkner

. Subjektive Krankheitstheorien im Gespräch [Subjective theories of illness in conversation]. Gesprächsforschung 2006; 7: 152–183.

11.

Kaptein

Schoones

Fischer

, et al. Illness perceptions in women with breast Cancer-a systematic literature review. Curr Breast Cancer Rep 2015; 7: 117–126.

12.

Bulun

. Uterine fibroids. N Engl J Med 2013; 369: 1344–1355.

13.

Bulun

Yilmaz

Sison

, et al. Endometriosis. Endocr Rev 2019; 40: 1048–1079.

14.

David

Alpheus

Kentenich

. Patients’ beliefs about the causes of myomas: a pilot study from a large European city. J Psychosom Obstet Gynaecol 2017; 38: 301–309.

15.

Blaxter

. The causes of disease: women talking. Soc Sci Med 1983; 17: 59–69.

16.

Orator

. The effects of endometriosis on South African women’s perceived quality of life. Masterarbeit, University of KwaZulu-Natal, KwaZulu-Natal, 2005.

17.

Chapron

Marcellin

Borghese

, et al. Rethinking mechanisms, diagnosis and management of endometriosis. Nat Rev Endocrinol 2019; 15: 666–682.

18.

Borah

Nicholson

Bradley

, et al. The impact of uterine leiomyomas: a national survey of affected women. Am J Obstet Gynecol 2013; 209: 319.e1–319.e20.

19.

Soliman

Singh

Rahal

, et al. Cross-sectional survey of the impact of endometriosis symptoms on health-related quality of life in Canadian women. J Obstet Gynaecol Can 2020; 42: 1330–1338.

20.

VAA

Thomas

Singh

, et al. A systematic review of the psychosocial impact of fibroids before and after treatment. Am J Obstet Gynecol 2020; 223: 674–708.e8.

21.

Lumbiganon

Rugpao

Phandhu-fung

, et al. Protective effect of depot-medroxyprogesterone acetate on surgically treated uterine leiomyomas: a multicentre case-control study. Br J Obstet Gynaecol 1996; 103: 909–914.

22.

Parazzini

Esposito

Tozzi

, et al. Epidemiology of endometriosis and its comorbidities. Eur J Obstet Gynecol Reprod Biol 2017; 209: 3–7.

23.

Barnes

Moss-Morris

Kaufusi

. Illness beliefs and adherence in diabetes mellitus: a comparison between Tongan and European patients. N Z Med J 2004; 117: 1–9.

24.

Moss-Morris

Weinman

Petrie

, et al. The Revised Illness Perception Questionnaire (IPQ-R). Psychol Health 2002; 17: 1–16.

25.

Kessler

Andrews

Colpe

, et al. Short screening scales to monitor population prevalences and trends in non-specific psychological distress. Psychol Med 2002; 32: 959–976.

26.

Spitzer

Kroenke

Williams

, et al. A brief measure for assessing generalized anxiety disorder: the GAD-7. Arch Intern Med 2006; 166: 1092–1097.

27.

Riedl

. Subjektive Krankheitstheorien beim Reizdarm-syndrom sowie Harn-und Analinkontinenz unter Berück-sichtigung klinischer und psychologischer Variablen [Subjective theories of disease in patients with irritable bowel syndrome and urinary and anal incontinence, taking into account clinical and psychological variables]. Dissertation, Charité - Universitätsmedizin, Berlin, 2013.

28.

Fan

Huang

Zhang

, et al. Psychometric validation of the Chinese version of the illness perception questionnaire-revised for women with stress urinary incontinence. J Obstet Gynaecol Res 2017; 43: 1305–1316.

29.

Kraft

von Georgi

Bohlmann

, et al. Laienätiologische Krankheitskonzepte und ihre mögliche Bedeutung für die Prävention [Lay concepts of disease etiology and their potential relevance to disease prevention]. Geburtshilfe Frauenheilkd 2004; 64: 504–512.

30.

Roick

Esser

Hornemann

, et al. Warum gerade ich? – Subjektive Krankheitsursachen und Zusammenhänge zu sozialen Faktoren und wahrgenommener Stigmatisierung bei Brust-, Prostata-, Darm- und Lungenkrebspatienten [Why me? - Subjective causes of disease and correlations with social factors and perceived stigmatization in patients with breast, prostate, colorectal or lung cancer]. Psychother Psychosom Med Psychol 2020; 70: 22–31.

31.

Riedl

Maass

Fliege

, et al. Subjective theories of illness and clinical and psychological outcomes in patients with irritable bowel syndrome. J Psychosom Res 2009; 67: 449–455.

32.

Förster

Taubert

. Subjektive Krankheitstheorien und Selbstregulation von Tumorpatienten [Subjective theories of disease and self-regulation in tumor patients]. Z Med Psychol 2006; 15: 117–127.

33.

Sillem

Teichmann

. Patientinnenzentrierte Aspekte der Endometriose [Patient-centered aspects of endometriosis]. Der Gynäkologe 2008; 41: 533–543.

34.

Bodden-Heidrich

Hilberink

Frommer

, et al. Qualitativ-inhaltsanalytische Studie zu pychosomatischen Aspekten der Endometriose/Qualitative research on psychosomatic aspects of endometriosis [Qualitative research on psychosomatic aspects of endometriosis]. Z Psychosom Med Psychother 1999; 45: 372–389.

35.

Bermejo

Muthny

. Laientheorien zu Krebs und Migration in Europa [Lay theories on cancer and migration in Europe]. Nervenheilkunde 2006; 25: 372–379.

36.

Faller

. Subjektive Krankheitstheorien: Determinanten oder Epiphänomene der Krankheitsverarbeitung? Eine methodenvergleichende Untersuchung an Patienten mit Bronchialkarzinom [Subjective theories of illness: determinants or epiphenomena of coping? A comparative methodological study of patients with bronchial carcinoma]. Z Psychosom Med Psychother 1993; 39: 356–374.

37.

Bittner

. Subjektive Krankheitstheorie, Krankheitsver-arbeitung und emotionales Befinden bei Patienten mit chronisch lymphatischer Leukämie [Subjective theory of illness, coping and emotional well-being in patients with chronic lymphocytic leukemia]. Dissertation, Julius-Maximilians-Universität Würzburg, Würzburg, 2005.

38.

Marteau

Weinman

. Self-regulation and the behavioural response to DNA risk information: a theoretical analysis and framework for future research. Soc Sci Med 2006; 62: 1360–1368.

39.

Crispim

PCA

Jammal

Murta

EFC

, et al. Endometriosis: what is the influence of immune cells? Immunol Invest 2021; 50: 372–388.

40.

Carpan

. Representations of endometriosis in the popular press: “The career woman’s disease”. Atlantis 2003; 27: 32–40.

41.

Wurm

Wiest

Tesch-Römer

. Theorien zu Alter(n) und Gesundheit [Theories on aging and health]. Bundesgesundheitsblatt Gesundheitsforschung Gesundheitsschutz 2010; 53: 498–503.

42.

Kauderer-Hübel

Zenz

Buchwalsky

, et al. Der Zusammenhang zwischen dem subjektiven Krankheitsbild von Herzinfarktpatienten mit Gesundheitsverhalten und Berufsaufnahme [The correlation between the subjective illness perception of heart attack patients and their health behavior and professional activity]. In: C

Bischoff

Zenz

(eds) Patientenkonzepte von Körper und Krankheit (Patient’s concepts of body and disease). Bern: Verlag Hans Huber, 1989, pp.60–74.

43.

Franz

Lujić

Koch

, et al. Subjektive Krankheitskonzepte türkischer Migranten mit psychischen Störungen ± Besonderheiten im Vergleich zu deutschen Patienten [Subjective concepts of disease in Turkish migrants with mental disorders ± particularities compared to German patients]. Psychiatr Prax 2007; 34: 332–338.

44.

Timmermans

Denollet

Pedersen

, et al. Patient-reported causes of heart failure in a large European sample. Int J Cardiol 2018; 258: 179–184.