Twin studies used to prove that the comorbidity of major depressive disorder with IBS is NOT influenced by heredity

Irritable bowel syndrome: an integrated explanatory model for clinical practice

BACKGROUND

Although irritable bowel syndrome (IBS) is a symptom-based diagnosis, clinicians' management of and communication about the disorder is often hampered by an unclear conceptual understanding of the nature of the problem. We aimed to elucidate an integrated explanatory model (EM) for IBS from the existing literature for pragmatic use in the clinical setting.

METHODS

Systematic and exploratory literature searches were performed in PubMed to identify publications on IBS and EMs.

KEY RESULTS

The searches did not identify a single, integrated EM for IBS. However, three main hypotheses were elucidated that could provide components with which to develop an IBS EM: (i) altered peripheral regulation of gut function (including sensory and secretory mechanisms); (ii) altered brain-gut signaling (including visceral hypersensitivity); and (iii) psychological distress. Genetic polymorphisms and epigenetic changes may, to some degree, underlie the etiology and pathophysiology of IBS and could increase the susceptibility to developing the disorder. The three model components also fit into one integrated explanation for abdominal symptoms and changes in stool habit. Additionally, IBS may share a common pathophysiological mechanism with other associated functional syndromes.

CONCLUSIONS & INFERENCES

It was possible to elucidate an integrated, three-component EM as a basis for clinicians to conceptualize the nature of IBS, with the potential to contribute to better diagnosis and management, and dialog with sufferers.

The epidemiology of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a functional condition of the bowel that is diagnosed using clinical criteria. This paper discusses the nature of the diagnostic process for IBS and how this impacts epidemiological measurements. Depending on the diagnostic criteria employed, IBS affects around 11% of the population globally. Around 30% of people who experience the symptoms of IBS will consult physicians for their IBS symptoms. These people do not have significantly different abdominal symptoms to those who do not consult, but they do have greater levels of anxiety and lower quality of life. Internationally, there is a female predominance in the prevalence of IBS. There is 25% less IBS diagnosed in those over 50 years and there is no association with socioeconomic status. IBS aggregates within families and the genetic and sociological factors potentially underlying this are reviewed. Patients diagnosed with IBS are highly likely to have other functional disease and have more surgery than the general population. There is no evidence that IBS is associated with an increased mortality risk. The epidemiological evidence surrounding these aspects of the natural history is discussed.

Childhood predictors of recurrent abdominal pain in adolescence: A 13-year population-based prospective study

OBJECTIVE

To investigate maternal and child emotional symptoms, physical health problems, and negative life events measured at children's age 18 months and 12 years as potential predictors for self-reported recurrent abdominal pain (RAP) in adolescents (14 years).

METHODS

A population-based prospective study conducted at child health clinics (preventive health care) in Norway followed a cohort of 916 mothers with children from children's age 18 months until adolescence. Child self-report was obtained from 12 years of age. Outcome measure was adolescent self-reported RAP.

RESULTS

Of 456 adolescents, 58 (13%) reported RAP. Of these, 36 (62%) were girls. By multivariate analyses, the following maternal factors predicted RAP in adolescence: psychological distress at children's age 18 months (OR, 2.5; 95% CI, 1.3-4.8) and a maternal history of psychological distress at children's age 12 years (OR, 3.2; 95% CI, 1.7-6.2). The following child factors measured at age 12 years predicted RAP in adolescence: abdominal (OR, 2.5; 95% CI, 1.3-4.9) and extraintestinal pain (OR, 2.3; 95% CI, 1.2-4.4) by maternal report, self-reported frequent extraintestinal pain (OR, 2.9; 95% CI, 1.4-5.9), and self-reported depressive symptoms (OR, 2.4; 95% CI, 1.1-5.1). Negative life events and physical health in mothers and toddlers did not predict RAP.

CONCLUSIONS

This is the first cohort study that finds maternal psychological distress in early childhood to predict RAP in their offspring 13 years later. Our results support that maternal psychological distress and preadolescent children's depressive and somatic symptoms may play a role in the development of RAP.

Is the DHEAS/cortisol ratio a potential filter for non-operable constipated cases?

Constipation is a significant manifestation of a number of psychological disorders. Published papers recommend using self-assessment questionnaires for discriminating psychological from non-psychological constipated patients before operating on them but reports from major surveys revealed that general practitioners failed to diagnose 70% of depressed patients using self-assessment questionnaires. Lower circulating concentrations of progesterone, 17-hydroxyprogesterone, cortisol, testosterone, androstenedione, and dehydroepiandrostenedione sulfate (DHEAS) during the follicular phase in constipated young women compared with respective controls were found during the follicular phase of the menstrual cycles. During the luteal phase of the cycle, reductions were identified in estriol, cortisol and testosterone in the constipated group. Likewise, circulating concentrations of DHEAS were found to be lower in depressed patients than comparable healthy controls. DHEAS/cortisol ratios in morning serum and salivary samples were lower than those retrieved during other times of the day in depressed patients. The idea of recognizing major depression in constipated patients by measuring DHEAS/cortisol ratios in saliva and serum may be plausible but this possibility needs to be confirmed in well-designed studies.

The probiotic Bifidobacteria infantis: An assessment of potential antidepressant properties in the rat

It is becoming increasingly apparent that probiotics are important to the health of the host. The absence of probiotic bacteria in the gut can have adverse effects not only locally in the gut, but has also been shown to affect central HPA and monoaminergic activity, features that have been implicated in the aetiology of depression. To evaluate the potential antidepressant properties of probiotics, we tested rats chronically treated with Bifidobacteria infantis in the forced swim test, and also assessed the effects on immune, neuroendocrine and central monoaminergic activity. Sprague-Dawley rats were treated for 14 days with B. infantis. Probiotic administration in naive rats had no effect on swim behaviours on day 3 or day 14 following the commencement of treatment. However, there was a significant attenuation of IFN-gamma, TNF-alpha and IL-6 cytokines following mitogen stimulation (p<0.05) in probiotic-treated rats relative to controls. Furthermore, there was a marked increase in plasma concentrations of tryptophan (p<0.005) and kynurenic acid (p<0.05) in the bifidobacteria-treated rats when compared to controls. Bifidobacteria treatment also resulted in a reduced 5-HIAA concentration in the frontal cortex and a decrease in DOPAC in the amygdaloid cortex. The attenuation of pro-inflammatory immune responses, and the elevation of the serotonergic precursor, tryptophan by bifidobacteria treatment, provides encouraging evidence in support of the proposition that this probiotic may possess antidepressant properties. However, these findings are preliminary and further investigation into the precise mechanisms involved, is warranted.

Genetic determination of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder. According to the Rome III criteria, IBS is defined as recurrent abdominal pain or discomfort for at least 3 d per month during the previous 3 mo associated with two or more of the following symptoms: improvement with defecation, onset associated with a change in the frequency of stool and/or onset associated with a change in form or appearance of stool. There is growing evidence regarding the genetic contribution in IBS, however the precise etiology of IBS is still unknown. The evaluation of the genetic influence is based on twin studies, familial aggregation and genetic epidemiological investigations. Most studies showed a concordance for IBS significantly greater in monozygotic than in dizygotic twins. The majority of the studies have shown that familial aggregation may represent exposures to a similar environment, as well as the influence of genetic factors. Whereas no specific gene has been identified in association with IBS, recent studies have noticed the importance of polymorphisms in the promoter region of the serotonin reuptake transporter gene, G-protein beta 3 subunit gene (C825T), cholecystokinin receptor (CCKAR gene 779T>C), and high-producer tumor necrosis factor genotype. Further studies are necessary to determine how genetic factors influence the clinical manifestations and therapeutical response in IBS patients.

Functional gastrointestinal disorders as a public health problem

The functional gastrointestinal disorders (FGIDs) are a heterogeneous group of chronic conditions that are considered to be important to public health because they are remarkably common, can be disabling, and induce a major social and economic burden. Despite the Rome consensus process, the line defining true abnormality from health is as yet imprecise. Furthermore, the concept that the FGIDs have no pathological or biochemical correlates is starting to unravel, and some candidate morphometric abnormalities (e.g. duodenal eosinophilia, colonic mastocytosis) have been documented. The quality of care that patients with FGIDs receive is not well understood, despite the high volume of patients seen in primary and specialty care. There are a remarkable number of symptom-based and disease-based co-morbidities that appear to be more common in those with FGIDs that are not alone explained by coexistent somatization. Whether there is any means of preventing the development of FGIDs post-infection is untested but has vast public health implications. Defining disease severity remains key to better understanding the public health impact of FGIDs; severity is probably influenced by the intestinal and extra-intestinal symptom burden, psychological distress and the impact on quality of life, but how these factors interact remains uncertain. An important future research direction must be to quantify at what risk level it is reasonable to prescribe a medication that may be dangerous, and stratify which subsets of patients with FGIDs would qualify for such an approach using objective well validated tools (e.g. based on accurately defining gradations of severity of disease). Finally, there are some reasons to suspect that there may be an increase in mortality in FGID sufferers; for example, unnecessary surgery or invasive testing has a small but not zero associated mortality, and this should be a factor in view of the high prevalence of disease.