The idea of a connection between the brain and the gut is not new. For years scientists have been studying the connection between the enteric (gastrointestinal) nervous system and the central nervous system. The enteric nervous system is able to act independently from the central nervous system, but is still connected to it. So, when one of these systems is dysfunctioning, it has a likelihood of affecting the other. This seems to hold true with a connection of gastrointestinal symptoms and bipolar depression.
The connection of the gastrointestinal nervous system to the brain exists through millions of neurons and neurotransmitters like serotonin, dopamine, glutamate and norepinephrine. All of these neurotransmitters are also affected in bipolar disorder. It makes sense that an imbalance in one of those areas might affect the other, thus increasing symptoms of both gastrointestinal and bipolar disorder simultaneously.
One group of researchers, led by Pontus Karling at the Department of Public Health and Clinical Medicine at Umeå University, conducted a study to see if symptoms of depression correlate with gastrointestinal symptoms.
The study looked at 10 years worth of medical records for 136 patients with bipolar disorder and 136 healthy controls. The participants were surveyed for symptoms of depression and anxiety including:
- Feeling tense
- Loss of interest
- Psychomotor retardation
- Depressed mood
The participants were then asked to rate gastrointestinal symptoms including:
- Abdominal pain
- Gastroesophageal reflux
The research showed a connection between high depressive symptoms and high gastrointestinal symptoms. Patients with bipolar disorder were more likely than the general population to see their primary care physician for gastrointestinal problems. This held true even when the patients were taking medication for their symptoms.
There were no significant differences between type I and type II bipolar disorder, but depressive symptoms correlated higher with gastrointestinal distress. People with bipolar II tend to have more depressive cycles than people with bipolar I, so may be more likely to experience GI problems.
Bipolar disorder patients not currently experiencing depression scored on par with the average population when it came to gastrointestinal symptoms, providing more evidence that the symptoms were linked.
There are a few possible reasons for a connection between the depressive and gastrointestinal symptoms. Corticotropin releasing hormone increases anxiety and is higher in people with bipolar disorder. It has also shown to physically affect the gut and increase gastrointestinal symptoms including the inhibition of upper-GI motility.
The researchers for the study suggest patients may need to be screened for increased bipolar depression when presenting with additional gastrointestinal symptoms.
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