LINK BETWEEN DEPRESSION AND IBS
High rates of anxiety
and depression amongst patients with irritable bowel syndrome (IBS) have led
many researchers to believe there could be a causal relationship between
psychological factors and IBS symptoms. Now, scientists in Germany have found
clear evidence that patients with IBS process pain signals from the gut
abnormally, and that disturbed brain responses to pain are particularly pronounced
in patients with more depression symptoms.
At the 22nd United
European Gastroenterology Week (UEG Week 2014) in Vienna, Austria, Professor
Sigrid Elsenbruch from the University of Duisburg-Essen in Germany, will be
presenting a new study which suggests that depression, but not anxiety,
contributes to the abnormal pain processing observed in IBS in a model that
addresses central pain inhibition during placebo analgesia. "Our study has
shown that patients with IBS are less able to suppress pain signals in the
brain coming from the bowel and that depression plays a role herein," she
says. "This study confirms the complex relationship between the gut and
the brain and shows that affective disorders may contribute to the development
or maintenance of disturbed pain processing in IBS."
IBS, anxiety and
depression
IBS is the most common
functional gastrointestinal disorder with prevalence rates of up to 23%
reported.2 The condition is characterised by recurrent
abdominal pain or discomfort, in combination with bloating and altered bowel
habits (e.g. diarrhea and/or constipation). Depression and anxiety frequently
co-exist with IBS, with a recent study reporting that 38% of IBS patients had
clinically-confirmed depression (compared with 6% of healthy controls) and 32%
had anxiety (compared with 13% of healthy controls).3
"The fact that so
many people with IBS have anxiety and depression has led many to speculate that
IBS is primarily a psychological, not a physical, disorder," says Prof.
Elsenbruch. "However, the condition is complex and most likely results
from an interplay between psychological and biological factors. In fact, we
don't really know whether anxiety and depression result from having IBS or
whether they contribute to the development or maintenance of symptoms. In many
patients, both possibilities may be true at the same time."
The
"brain-gut" axis in IBS
There has been
significant scientific interest in the role of central nervous system
mechanisms along the "brain-gut" axis in IBS. Neuroimaging studies
have demonstrated that neural processing of visceral stimuli (i.e. stimuli
generated from internal organs such as the intestine) is altered in IBS, with
many IBS patients showing lowered pain thresholds.4 In Prof.
Elsenbruch's latest study, painful rectal distensions were performed using a
pressure-controlled barostat system in 17 patients with IBS and 17 sex- and
age-matched healthy controls.1 Neural activation in
pain-related brain areas was assessed using functional MRI (fMRI) while
subjects received sequential intravenous administrations of saline and what
they thought was an anti-spasmolytic drug (but was actually a saline placebo),
in order to observe activation patterns during a typical placebo pain response.
The fMRI results in
the healthy volunteers demonstrated reduced neural activation in pain-related
brain areas during both the saline and sham treatment (placebo), indicating
significant central pain inhibition. However, there was no such inhibition in
the group of IBS patients, suggesting a deficiency in central pain inhibitory
mechanisms in IBS. Interestingly, higher depression (but not anxiety) scores on
the Hospital Anxiety and Depression Scale (HADS) were associated with reduced
central pain inhibition in this study.
"Our findings
suggest that patients with IBS do not process visceral pain signals in the same
way as healthy people and are unable to suppress pain signals in the brain and,
as a result, experience more pain from the same stimuli," says Prof.
Elsenbruch. "The fact that the presence of depression was associated with
altered brain responses suggests that depression may contribute to these
abnormal pain processes in IBS patients."
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