Irritable bowel syndrome (IBS) has been associated with high prevalence of psychological disorders. However, it remains unclear whether IBS and each of its subtypes (predominant diarrhea IBS-D, constipation IBS-C, mixed IBS-M) are associated with higher anxiety and depressive symptoms levels. This study aimed to determine the associations of IBS and each of its subtypes with anxiety and/or depression. We conducted a systematic review and meta-analysis using five electronic databases (PubMed, PsychINFO, BIOSIS, Science Direct, and Cochrane CENTRAL). We selected case-control studies comparing anxiety and depression levels of patients with IBS to healthy controls, using standardized rating scales. Outcomes were measured as random pooled standardized mean differences (SMD). Ten studies were included in our analysis (885 patients and 1,384 healthy controls). Patients with IBS had significant higher anxiety and depression levels than controls (respectively, SMD = 0.76, 95 % CI 0.47; 0.69, p < 0.01, I2 = 81.7 % and SMD = 0.80, 95 % CI 0.42; 1.19, p < 0.01, I2 = 90.7 %). This significant difference was confirmed for patients with IBS-C and -D subtypes for anxiety, and only in IBS-D patients for depression. However, other IBS subtypes had a statistical trend to be associated with both anxiety and depressive symptomatology, which suggests a lack of power due to the small number of studies included. Patients with IBS had significantly higher levels of anxiety and depression than healthy controls. Anxiety and depression symptomatology should be systematically checked and treated in IBS patients, as psychological factors are important moderators of symptom severity, symptom persistence, decisions to seek treatment, and response to treatment.

Polyunsaturated fatty acids seem to have the best benefit/risk ratio profile but proved their effectiveness only in MDD. A number of anti-inflammatory drugs are available as adjunct treatment for treatment-resistant patients with MDD, schizophrenia and bipolar disorder. If used with caution regarding their possible side-effects, they may be reasonable therapeutic alternatives for resistant symptomatology.