Researchers at the State University of New York, Buffalo, New York, tested effects of cognitive behavioral therapy (CBT) in adults diagnosed with IBS, a condition characterized by bouts of abdominal cramps, bloating, and changes in bowel habits — diarrhea or constipation, or sometimes alternating episodes of both [Lackner et al. 2010]. It is estimated that as many as 1 in 5 U.S. adults have symptoms of IBS, with women being affected twice as often as men.
The study included 71 individuals (aged 18-70 years) whose IBS symptoms were of at least moderate severity. Patients were assigned randomly to undergo either a wait list control, 10 weekly 1-hour sessions of CBT, or four 1-hour CBT sessions over 10 weeks. CBT aims to help people with IBS recognize their symptom triggers and learn practical ways to manage them. For example, as one task patients "self-monitored," keeping close track of their symptoms, the circumstances under which they occurred, and their thoughts, feelings, and physical responses before and after the flare-ups.
Across the two CBT groups, 30% of patients showed a rapid response within 4 weeks, exhibiting relief of pain, adequate amelioration of bowel symptoms, and a significant decrease in total IBS severity scores on a questionnaire. Surprisingly, the researchers found that a rapid response was just as likely in the 4-session group — where patients were only on their second therapy session at week four. Another 28% were considered CBT-treatment-responders at the 3-month mark. This was a small study and it is not known how long the favorable outcomes might persist over time; furthermore, the exact mechanisms of how CBT might modify the disease are unclear at present.
Meanwhile, in separate but related research, investigators from Toronto, Canada, used structural magnetic resonance brain imaging, comparing 16 IBS patients with 16 age-matched healthy subjects, to examine abnormalities resulting from long-term IBS [Blankstein et al. 2010]. Significant differences were found in the thicknesses of vital limbic-system structures in those with IBS.
Specifically, patients with IBS exhibited increased gray matter in the thalamus region and thinning of the cingulate cortex. Additionally, patients with prefrontal cortex thickening expressed less pain catastrophizing. Those with shorter-term duration of IBS pain had thinning of the insular cortex but this was of a more normal thickness in patients with long-term IBS. [Illustration* depicts the involved limbic structures.]
COMMENTARY: The brain imaging studies provide new insights into IBS, and perhaps all chronic pain, through evidence of changes in brain structure that coincide with functional abnormalities. For example, patients with IBS appear to have increased thalamic gray matter, which may be related to the association of IBS with stress and altered function of the hypothalamic-pituitary-adrenal axis. Other abnormalities discovered during imaging may suggest either vulnerabilities in certain individuals predisposed to IBS, or they may be a structural consequence of chronic disease over time. Overall, the structural changes in the presence of IBS appear to represent the remarkable plasticity of the brain; that is, the brain's ability to remodel and reorganize itself throughout life in response to internal and external stimuli.
Psychological therapies — of which CBT is but one — would expectedly impact limbic structures that are involved with stress and affective responses to painful stimuli [see earlier discussion of the limbic system here]. The success of CBT in the study by Lackner and colleagues is noteworthy, and it could be important to know if such therapy achieves its effects by modifying the structural limbic abnormalities found by Blankstein et al. Hopefully, further research will determine if this is the case and allow for even more targeted and effective psychological interventions to be designed and implemented.
>Blankstein U, Chen J, Diamant NE, Davis KD. Altered brain structure in irritable bowel syndrome: potential contributions of pre-existing and disease-driven factors. Gastroenterology. 2010(May);138(5):1783-1789 [abstract here].
> Lackner JM, Gudlesk GD, Keefer et al. Rapid response to cognitive behavior therapy predicts treatment outcome in patients with irritable bowel syndrome. Clin Gastroenterology Hepatol. 2010(May);8(5):426-432 [abstract here].
*Illustration above is based on this recommended resource: Apkarian AV, Bushnell MC, Treede R-D, Zubieta J-K. Human brain mechanisms of pain perception and regulation in health and disease. Eur J Pain. 2005;9:463-485 [full article here]. Brain image adapted from ATI. For additional information on pain and brain structures, see: Apkarian Lab website [here].