Patients with IBD, which causes the lining of the gut to become inflamed, are accepted to have higher rates of depression than the general population, but whether this makes their disease worse has been unclear.
Now, researchers from Imperial College London and St George's, University of London investigating the link say there is limited evidence to support the idea that being depressed leads to a deterioration of patients' bowel conditions. However, they add that the limited available evidence from their review suggests a stronger link with one form of the condition – Crohn's Disease – over another.
The findings could lead to better treatment of IBD and ultimately, say the researchers, to cost savings for the healthcare system.
Crohn's Disease and Ulcerative Colitis, the two main forms of IBD, are long-term conditions in which sections of the gut become inflamed, with common symptoms including diarrhoea, abdominal cramps and extreme tiredness.
While patients can be relatively unaffected by the disease during periods of remission, flare-ups – periods in which the underlying inflammation spikes – can lead to a worsening of their symptoms and disrupt their lives.
There is no cure and patients may be prescribed courses of steroids and immunosuppressant drugs to calm the inflammation, but in the worst cases, the disease can result in surgery to remove sections of the gut.
The idea that depression and inflammation may be linked has gained some traction in the scientific community, with evidence to suggest those with chronic low mood also have high levels of stress hormones and inflammatory markers in their blood. However, the association between depression and IBD is unclear.
Investigating the potential implications for IBD patients, researchers from Imperial and St George's carried out a systematic review to see if depressive state was linked with a worsening of their condition.
Reviewing the evidence
During the review, they extracted relevant information from 11 published studies involving patients with IBD, using whether or not their disease worsened as the primary outcome. Three of the studies looked only at patients with UC, four studies looked only at patients with Crohn's Disease, and the remaining four studies looked at both conditions.
Analysis of this pooled data revealed a lack of evidence to support the idea that depression makes IBD worse. However, the researchers note that there was evidence to suggest depression has more of an effect on symptoms in patients with Crohn's Disease, compared with Ulcerative Colitis.
Dr Sonia Saxena, from the School of Public Health at Imperial, explained: "This study is about investigating whether stress and depression make inflammatory conditions worse."
She added: "IBD is associated with major disability during flare ups and patients may have to take expensive drugs, including immunosuppressants, which can have significant side effects and impact on their quality of life.
"We are still trying to untangle how depression and inflammatory bowel conditions could be linked. If being depressed makes things much worse, it's important we are able to diagnose that. Essentially, if we could make a patient's gut inflammation better by treating their depression, we could potentially avoid these side effects and improve patients' quality of life."
Higher rate of depression
Nearly 300,000 people in the UK have IBD (Crohn's and Ulcerative Colitis), with Ulcerative Colitis being the more common form. Those with IBD have a higher rate of depression than the general population, with some studies reporting prevalence as high as one in five patients.
The researchers highlight that a lack of randomised controlled trials and relatively small numbers of patients in the studies reviewed make it difficult to draw firm conclusions, and stress that further research is needed.
Dr Christopher Alexakis, a gastroenterologist at St George's and first author of the study, said: "Our findings suggest that screening for depression in IBD be part of the formal work up of patients with IBD."
He added: "The question of whether depression worsens outcomes is more difficult to answer. The qualitative data implies that in patients with disease in remission, depression probably doesn't influence outcomes. However, looking at all the studies together, there may be some evidence that depression may worsen outcomes in Crohn's Disease, although this relationship needs to be examined in more detail."
If future research showed that depression worsened the condition in a subset of patients with Crohn's Disease, prescribing antidepressive drugs and psychotherapy could help to improve their health outcomes.
Future studies will look further into the link between depression and IBD as well as the effect of treating depression and outcomes in patients.
Dr Saxena explained: "We're trying to answer basic questions on current practice for patients with IBD, including what proportion are depressed, the proportion prescribed medications for their depression and what happens when they are prescribed these medications."
"If we find that these antidepressive drugs work well on the gut, we want to find out why that's happening and whether that's because of a direct action on the gut, or whether it's that if you 'feel better', you have less inflammation in the gut."
Explore further: Depression tied to Crohn's disease flare-ups
More information: C. Alexakis et al. Systematic review and meta-analysis: the impact of a depressive state on disease course in adult inflammatory bowel disease, Alimentary Pharmacology & Therapeutics (2017). DOI: 10.1111/apt.14171