CD: Almost half of the total questionnaires (52.2%, 522 of 1000) were returned. Since six questionnaires were excluded due to missing data, a total of 516 questionnaires were usable for further analyses. Of these, 213 (41.3%) of the respondents indicated that the CD diagnosis was made by duodenal biopsy, 37 (7.2%) by serological tests (CD-specific antibodies), 34 (6.6%) by stool tests (transglutaminase antibodies), and 232 (45.0%) by duodenal biopsy plus serological tests. The 445 patients reporting a biopsy-proven CD were included for further analysis. HADS data were available from 441 patients. Patients who took part in the survey did not differ from those who did not send back the questionnaires in terms of age, sex and geographical region of Germany.
IBD: The total response rate was 63.4% (550/868). Of the 550 returned questionnaires, 128 were excluded from analysis due to colo- or ileostoma (n = 59), uncertain diagnosis (n = 16), impossibility of calculation of GIBDI because of missing data (n = 51), missing HADS data (n = 6) or missing declaration of consent (n = 2). Patients with moderate (n = 40) and severe (n = 10) disease activity were excluded from comparison. The IBD group thus consisted of 366 patients; 50% were females. To ensure a sex-matched comparison with CDs, 131 randomly selected male patients were excluded from analysis. Of the 235 included for comparison, 138 (56.3%) patients were in remission, 107 (43.7%) patients had a slight disease activity.
To check for a possible selection bias, the data of responders were compared to the known structural data on all outpatients of the Tübingen outpatient clinic (place of residence, diagnosis, gender, age, duration of disease, age at disease onset, number of consultations in 2000). No indication of systematic selection effect was found in respondents vs non-respondents. Likewise, there was no difference in terms of gender and age in patients from the departments of the Saarland University Clinics who did and did not participate. There were no significant differences in the demographic variables and HADS scores of the patients included in and excluded from comparison.
GP: The initial sample consisted of 2952 subjects of whom 2037 (69.0%, n = 1142 women) fully participated. Forty-five subjects < 18 years were excluded. Thus the GP sample consisted of 1992 adult persons. Of these, 441 GPs (persons of GP) (346 women, 95 men) were randomly selected for comparison. There were no significant differences in the demographic variables and HADS scores of the persons included in and excluded from comparison.
Medical and demographic data of the celiac sample
The sample consisted of 78.5% women. The most frequently self-reported CD-associated diseases were dermatitis herpetiformis Duhring (n = 45, 9.3%) and autoimmune thyroiditis (n = 25, 5.6%). Type 1 diabetes mellitus was reported by 2 patients (0.5%). There were no gender differences in the demographic and medical variables assessed. The level of anxiety (P = 0.0002) and the frequency of a probable anxiety disorder (P = 0.01) were higher in female than in male CDs (Table ).
Demographic data of the celiac disease sample with gender comparison
Predictors of anxiety and depression in CD
Anxiety was significantly predicted only by female gender (R2 = 0.07, P = 0.01). Depression was not significantly predicted by any of the medical and sociodemographic variables tested.
Predictors of a probable anxiety and depressive disorder
Because only in 2/8 patients with CD and diabetes mellitus type 1 an anxiety or depressive disorder was diagnosed, this variable was not entered into the regression analysis.
Anxiety disorder: The model correctly classified 84.8% of the patients. Only female sex (OR = 3.6, 95% CI: 1.3-9.4, P = 0.001) was associated with a probable anxiety disorder. Living alone (OR = 0.45, 95% CI: 0.20-0.99, P = 0.05) was associated with a reduced risk of a probable anxiety disorder. The omnibus test of the model coefficient was significant (χ2 = 20.2, P = 0.009). The level of significance in the Hosmer Lemeshow test was P = 0.5 (χ2 = 6.9) above the predefined P-value of 0.05, thus confirming the adequacy of the model.
Depressive disorder: None of the variables tested was significantly associated with a probable depressive disorder. The omnibus test of the model coefficient was not significant (χ2 = 13.5, P = 0.10).
Comparison with GP and patients with chronic IBD
In the CD sample, there were more patients of a higher social class than in the IBD sample (χ2 = 14.0, P = 0.006). There were no differences between the samples in the other variables tested (Table ).
Comparisons of patients with celiac disease with patients with inflammatory bowel disease in remission or having slight disease activity and with subjects of the general population
The level of anxiety in CDs (6.7 ± 4.0) and IBDs (6.9 ± 3.7) was higher than that seen in GPs (4.6 ± 3.6) (all P < 0.001). After adjusting for social class there was no significant difference in the anxiety level between CDs and IBDs (F = 1.3, P = 0.3).
The level of depression in CDs (4.1 ± 3.6), IBDs (4.6 ± 3.4) and GPs (4.2 ± 3.8) did not differ (P = 0.3). After adjusting social class index, IBDs reported higher depression than CDs (F = 3.9, P = 0.02).
The frequency of a probable anxiety disorder was higher in CDs (15.4%) and IBDs (14.0%) than in GPs (5.7%) (all P < 0.001). There was no difference in the frequency of a probable depressive disorder between the three groups (P = 0.1).