IBS and Depression - What's the link? The Gut-Brain Connection

IBS and depression

Irritable bowel syndrome, also sometimes called 'spastic colon', is a functional gastrointestinal disorder. It is a ‘functional’ disorder as it presents no physical abnormalities observable in the GI tract though causes physical symptoms. IBS patients typically experience bloating, abdominal pain, cramping, and either constipation or diarrhea. IBS is common, affecting 1 in 7 individuals globally.(1)

Depression is a psychiatric disorder of low mood and persistent negative feelings, and severely impacts quality of life. There are several forms of depression as defined by the Diagnostic and Statistical Manual for Mental Disorders (DSM-5), including postnatal depression, bipolar disorder and seasonal affective disorder.(2) Depression affects 10% of the population in the United States, and the psychological factors in depression are believed to interact with IBS.(3)

Comparison of symptoms

IBS causes symptoms experienced in the GI tract associated with lower motility (speed of transit of food through the GI tract), such as abdominal pain, whereas depression is a psychiatric disorder with mental health impacts such as negative thoughts and low mood. However, both conditions cause fatigue.

IBS

• Bloating and gas
• Abdominal pain
• Constipation/diarrhoea
• Changes in stool consistency
• Food intolerance
• Fatigue

Depression

• Persistent sad, or ‘empty’ feeling
• Sense of helplessness
• Sense of worthlessness
• Suicidal thoughts
• Reduced concentration
• Sense of guilt
• Fatigue

The overlap between IBS and depression

IBS and mood disorders, including depression, are common conditions and show significant overlap. This is because symptoms of IBS appear to affect mental health, and vice-versa.

The rate of lifetime depression in patients with IBS is 60%, three times higher than the rate in healthy individuals of 20%.(4) This makes depression the most common psychiatric disorder in IBS. In patients who suffer major depression, the rate of IBS is 27%, which is roughly double the normal rate.(5) Hence, there is a clear link between mood disorders and the digestive system.

Does IBS cause depression?

IBS does not cause mood disorders but may worsen symptoms of depression. The severity of IBS symptoms such as bloating and cramping impact quality of life significantly and may lead to the development of mental health conditions like depression and anxiety. According to a recent survey, up to 50% of people with IBS would give up their mobile phone in exchange for 1 month of relief.(6) This data indicates how severely irritable bowel syndrome may impact a patient's mental health and promote psychological symptoms.

IBS may also worsen symptoms of depression by influencing behavior. Concern over bowel movements or symptoms of IBS may lead patients to seek isolation and avoid social activities. These changes in behavior may cause psychological symptoms such as loneliness and helplessness, that contribute to feelings of depression.

How does depression affect IBS?

The symptoms of depression may worsen the symptoms of IBS. Depressed individuals report higher levels of sensitivity to pain, experiencing sensations in the GI tract more strongly. This leads to a more intense experiencing of symptoms of IBS such as abdominal pain, bloating and cramping.(7)

Specific symptoms of depression such as fatigue may make it harder for IBS patients to adjust their lifestyle to relieve symptoms of IBS, such as adjusting their diet or seeking other treatment options.

Overlap between IBS and Depression

IBS and symptoms of depression clearly influence one another. However, the biological nature of the link between the two is not fully understood. The gut-brain axis, which is the connection between the GI tract and the nervous system, as well as the biopsychosocial model are two concepts that may help to explain the connection.

The gut-brain connection

There is a two-way communication network between the GI tract and the brain, known as the mind-gut connection or gut-brain axis. This two-way connection is important to understanding the link between IBS and depression.7

The brain and gut communicate through the nervous system and digestive system. The GI tract contains over 500 million neurons that receive signals and transmit them to the brain via the vagus nerve. This information is processed in the brain and may affect conscious experience, in some cases leading to symptoms of IBS.

The gut-brain axis and its two-way channel of communication have been demonstrated in experiments using mouse models. When external stress was applied, changes to the composition of gut bacteria (microbiome) was observed. This new pattern of bacteria then lead to depressive behavior in the mice.(8)

However, the precise mechanism for such gut-brain effects is still being unraveled. The neurotransmitter serotonin is thought to play a role in linking IBS and depression.

Probiotics for depression and IBS

Further evidence for the gut-brain connection comes from the use of probiotics for depression and IBS. Probiotics change patterns of bacteria in the gut, which in turn have been shown to improve symptoms of depression and IBS.

A recent study showed depression scores improved in twice as many patients taking probiotics compared to those taking placebo. Brain scans using MRI and confirmed different that levels of activation in brain areas associated with mood regulation differed between the groups. These findings suggest that probiotics had an anti-depressive effect on the GI tract and the nervous system, providing evidence for the gut-brain connection.(11)

The biopsychosocial model

The biopsychosocial model (1980) explains how the gut (digestive system) can affect the brain (nervous system) and vice-versa, and how environmental factors contribute. Put simply, the model encapsulates the connection between social, biological and psychological phenomena in humans.(12)

The biopsychosocial model explains how genetics and environmental stress may contribute to the development of both mood disorders and digestive disorders. Trauma, in particular, has been shown to trigger both psychiatric disorders and IBS. Therefore, the model may help to explain the strong association between mental health and the GI tract, by suggesting traumatic events underlie both conditions.(13)

Trauma – the cause of IBS and depression?

Trauma, as explained by the biopsychosocial model, may represent a link between depression and IBS. Rates of physical or emotional trauma are high IBS patients, and up to 50% of patients with IBS have experienced trauma; twice the rate of healthy controls. Some researchers hypothesize that trauma is the source of IBS in most patients.(14)

Forms of trauma include sexual assault, vehicle accidents and death of a loved one, and such events also elevate the risk of mood disorders such as depression. Hence, the onset of trauma may lead to a vicious cycle of depression and IBS, as both are thought to arise following trauma.

Treatment options

Mood disorders and IBS are complex, and there is currently no cure for either. However, several therapies treat IBS or symptoms of depression or both. Depression is often treated with antidepressant medication such as SSRIs, therapies such as hypnotherapy or cognitive behavioral therapy or brain stimulation.

The gut-brain connection explains how psychotherapies like cognitive behavioral therapy (CBT) and hypnotherapy are also effective treatments for IBS. In some ways, this role of gastroenterologists resembles that of counselors in trying to soothe the ‘second brain’ that is the nerves of the GI tract. In this way, psychological therapies can treat both depression and IBS together. Below outlines common treatments for IBS and depression.

1. Antidepressants

Although considered an off-label use, antidepressants are frequently prescribed for IBS. These medications relieve abdominal pain and restore bowel movements by altering serotonin levels. Generally, a lower dosage of medication is prescribed for IBS than for psychiatric disorders.

Two most common antidepressants for IBS are:

• Selective serotonin reuptake inhibitors (SSRIs), including Prozac (fluoxetine) and Cipramil (citalopram).(15)
• Tricyclic antidepressants, such as Desipramine (Norpramin) and Nortriptyline (Pamelor). Tricyclic antidepressants are a second-line treatment for depression after SSRIs.(16)

SSRIs are also usually the first choice since there are fewer side effects than other antidepressants. These medications are particularly effective in reducing constipation in IBS. Tricyclic antidepressants are a second-line treatment for depression useful in diarrhea-predominant IBS.(15,16)

2. Cognitive behavioural therapy

CBT is a common treatment option for depression, and now widely used to treat functional gastrointestinal disorders. This form of therapy teaches patients to recognize negative thoughts and replace them with positive, realistic ones. Several CBT techniques are particularly useful for treating symptoms of IBS:

• Relaxation strategies such as diaphragmatic breathing activate the parasympathetic nervous system, which can normalize the function of the GI tract.
• Cognitive restructuring can help patients build awareness of distorted thoughts  in IBS. This may lessen catastrophizing and stress and reduce symptoms of IBS.(17)
• Exposure techniques in which patients face fearful situations can help eliminate fearful responses to gastrointestinal sensations.(17)

CBT is has been found to ease symptoms of IBS in most patients, and this is likely to correlate with fewer symptoms of depression.

3. Low FODMAP diet

Diets that eliminate common trigger foods of IBS have been shown to improve symptoms of functional gastrointestinal disorders. The low FODMAP diet was developed by Monash University for treating IBS and has been shown effective in numerous studies. Broadly, the diet eliminates short-chained carbohydrates, which are found in many fruits, vegetables, and grains. Relieving symptoms of IBS through dietary intervention may reduce symptoms of depression and improve quality of life.(18)

4. Hypnotherapy

Hypnotherapy has been used to treat numerous health conditions, such as chronic pain and smoking addiction. Hypnotherapy has recently been adapted to treat IBS, and is believed to work by acting on the subconscious mind to improve motility in the GI tract and reduce the sensitivity of the gut. A clinical trial recently showed that six weeks of hypnotherapy reduces IBS symptoms in 70% of patients, while also reducing psychological scores for depression.(19) The mobile app Nerva uses this approach to help people with IBS self-manage their IBS symptoms.

There have been few studies evaluating hypnotherapy in depression. However, improvements to patients with anxiety disorders using hypnotherapy suggest a promise for hypnotherapy in depression.(20)

The Wrap Up

The link between mood disorders and IBS is complex. Both conditions are unpleasant and may interfere with daily activities. What remains clear is the importance of treating the two conditions together, rather than individually, and the value of adding psychological treatments to standard medical care. If you experience symptoms of depression or IBS, it is best to consult your doctor for a diagnosis. You may be referred to a specialist in psychiatric disorders so both conditions may be treated together.