Introduction
Psychiatric comorbidity, most commonly measured as severity of anxiety and depression symptoms, has been found to be associated with IBS symptom severity. However, available studies have rarely assessed the importance of formal psychiatric diagnoses on disease burden in IBS. In this analysis from a pan-European project (DISCOvERIE) focusing on the relevance of comorbid mental (anxiety, depression) and/or somatic (fibromyalgia, chronic fatigue syndrome) diagnoses in patients with IBS, we aimed to assess whether presence of psychiatric diagnoses according to the DSM-5 criteria has an impact on overall symptom severity in IBS.
Aims & Methods
We included patients with IBS according to the Rome IV criteria from nine different European centers. Exclusion criteria included the presence of severe psychiatric disease (i.e. bipolar disorder, schizophrenia, autism spectrum disorder, schizoaffective disorder, or organic psychiatric disorder demanding psychopharmacotherapy, psychiatric day-care or inpatient treatment). The patients underwent The Mini International Neuropsychiatric Interview (MINI) to diagnose major psychiatric diagnoses (a total of 17). Fibromyalgia and chronic fatigue were diagnosed by current diagnostic criteria. They also filled in questionnaires assessing Severity of IBS symptoms (IBS-SSS), depression (PHQ-9), anxiety (GAD-7), somatic symptoms (PHQ-15), and fibromyalgia symptoms (FIQ). Severity of symptoms were compared between groups with increasing number of psychiatric diagnoses using One-Way Between-Groups ANOVA with linear trend analysis.
Results
In total, 617 patients with IBS (median age 44 years, 80% females) were included. Among the IBS patients, 269 (44%) had none of the mental (anxiety, depression) or somatic (fibromyalgia, chronic fatigue syndrome) comorbidities (median age 44 y, 75% females), whereas 174 (28%) had comorbid mental disorder only (median age 38 y, 82% females), 49 (8%) had comorbid somatic disorder only (median age 50 y, 86% females) and 124 patients (20%) had mental and somatic comorbidities (median age 47 y, 86% females). The most common psychiatric diagnoses among the IBS patients were depression (n=284), generalized anxiety disorder (n=145) and panic disorder (n=38) followed by agoraphobia (n=23) and social anxiety (n=19). Participants were divided into four groups according to the number of psychiatric diagnoses (0, 1, 2, and ≥3). The severity of IBS, depression, anxiety, somatic, and fibromyalgia symptoms all increased gradually with increasing number of psychiatric diagnoses. The effect sizes (partial eta squared) were small for IBS symptoms, medium for somatic symptoms and large for the other severity measures (Table 1).
Table 1: Symptom severity in groups with increasing number of psychiatric diagnoses
| No. of psychiatric diagnoses (MINI)
| Partial eta squared
| P-value
|
0 (n=355)
| 1 (n=83)
| 2 (n=84)
| ≥3 (n=95)
|
IBS symptom severity (IBS-SSS)
| 230 [170–310]
| 267 [210–339]
| 254 [184–348]
| 282 [232–351]
| 0.017
| 0.002
|
Depression (PHQ-9)
| 4 [1–8]
| 8 [4–13]
| 10 [3–15]
| 13 [8–17]
| 0.170
| <0.001
|
Generalized anxiety (GAD-7)
| 4 [1–7]
| 5 [3–9]
| 8 [5–14]
| 11 [8–15]
| 0.227
| <0.001
|
Somatic symptoms (PHQ-15)
| 10 [7–14]
| 13 [10–16]
| 13 [8–19]
| 15.5 [12–21]
| 0.097
| <0.001
|
Fibromyalgia symptoms (FIQ)
| 16 [6–29]
| 31 [17–45]
| 37 [19–55]
| 45 [27–62]
| 0.154
| <0.001
|
Scores presented as medians with interquartile range.
Conclusion
This multicenter pan-European study shows that psychiatric diagnoses are common among IBS patients and that the overall disease burden in IBS is associated with psychiatric comorbidity. These findings highlight the importance of taking psychiatric comorbidity into consideration and to acknowledge the relevance of gut-brain axis interactions when managing patients with IBS.
Disclosure
Hans Törnblom: Consultant or advisory board member for Allergan, Cinclus Pharma, Medifactia, and VIPUN and as a speaker for Tillotts, Takeda, and Shire.
Daisy Jonkers: Part of the work of DJ, outside the submitted work has been financed by public-private partnership grants of Top Knowledge Institute (TKI) Agri&Food and Health Holland, by the Carbokinetics program as part of the NWO-CCC Partnership Program, by Organic A2BV/Mothersfinest BV.
