04/04/2016 12:28 EDT | Updated 04/05/2017 05:12 EDT

The Physical Symptoms Of Depression And Anxiety Are Real

I have heard the question, "Are you saying it's all in my head?" countless times, so I now begin discussions about physical symptoms associated with depression and anxiety with, "Just because your symptoms aren't caused by an injury or an infection doesn't mean they're not real."

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Paul, a lawyer, says he's had an upset stomach and diarrhea "forever". The symptoms are especially unpleasant when he's presenting to colleagues at work, but they can also happen suddenly, with no provocation or warning. No medical cause has been found despite a full work-up and no treatment has helped. He now dreads going to work, mostly because he's terrified of being more than a few steps away from a bathroom. As a result, Paul has limited all of his professional and social activities. He was incensed when his doctor asked him if he was experiencing anxiety, and barked, "Of course I'm anxious! Wouldn't you be if you had explosive diarrhea for no reason?"

Michelle, a teacher, has been assessed over the last year for complaints of debilitating chronic pain, fatigue, and insomnia. No medical reason has been found, despite many examinations and tests. She attempted to fix the problem herself, changing her mattress, exercising, and restricting caffeine, alcohol, and other foods, but nothing helped. When her doctor asked her to complete a questionnaire that assessed her mood, she became enraged and felt betrayed. "You don't believe me", she cried. "Do you think this is all in my head?"

I have heard the question, "Are you saying it's all in my head?" countless times, so I now begin discussions about physical symptoms associated with depression and anxiety with, "Just because your symptoms aren't caused by an injury or an infection doesn't mean they're not real."

Pain hurts, whether it's caused by arthritis or depression. Diarrhea is uncomfortable, unpleasant and at times embarrassing, whether it's due to a bacteria or anxiety. The proof is in the toilet. The diarrhea is real. Depressed and anxious patients may experience many other kinds of physical symptoms as well, including headaches, shortness of breath, chest pressure, dizziness or feeling faint, and crushing fatigue.

Our brains control our bodies. Each breath, every movement, every sensation occurs due to the coordinated activity of various brain regions. The brain sends information to and gathers information from the rest of the body via nerves. Pain and other physical experiences result from brain activity. Pain is a psychological experience and does not require a physical stimulus (like an injury), so pain truly is "all in your head", no matter the cause.

Physical symptoms (AKA: somatic symptoms) of depression and anxiety are extremely common. Estimates of the frequency of painful physical symptoms associated with depression range from 50-75%, and people suffering from chronic pain have much higher rates of depression than the general population. Unfortunately, for more than half of patients who have both depression and pain, the depression diagnosis is missed.

When accompanied by painful symptoms, depression is often more chronic (on average lasting 6 months longer), more severe, more difficult to treat and more likely to recur. There is a clear correlation between the intensity of pain and the intensity of depression symptoms. In my practice, if I do not effectively address complaints of pain, I cannot adequately treat depression.

There are several reasons why pain and depression co-occur so frequently. Brain imagining has shown that depressed patients may have an impaired ability to modulate their pain experience , which means they are more sensitive to pain. Essentially, pain hurts more when you're depressed. The amygdala is the brain region responsible for responding to frightening or dangerous experiences.

Activation of the amygdala is necessary to react quickly to a scary situation, however, it is excessively activated in depressed and anxious brains. The amygdala also plays an important role in how we experience pain and an overactive amygdala can heighten pain intensity .

Some of the same brain chemicals (neurotransmitters) associated with anxiety and depression are also important for pain perception, especially norepinephrine (NE). Some of the antidepressants that increase NE are also very helpful for managing pain symptoms, even in the absence of depression symptoms.

The bowel symptoms Paul experiences are also commonly associated with depression and anxiety. Functional gastrointestinal disorders (FGIDs) are chronic or recurrent bowel symptoms that are not explained by any medical cause. FGID patients have a "hypersensitive gut" and complain of a combination of symptoms that may include nausea, vomiting, bloating, diarrhea, constipation, and pain. More than 90% of patients with irritable bowel syndrome (a FGID) also have mood and anxiety symptoms.

The causes of FGIDs are very similar to the causes of depression: they're biopsychosocial (see my March 21, 2016 blog). Biologically, FGIDs are associated with stress and anxiety, which provokes inflammation. This is caused in part by activation of mast cells in the gut. Activated mast cells release chemicals like histamine, which affect the nerves supplying the gut, causing changes in how the gut moves (e.g. increased motility= diarrhea, decreased motility= constipation) and how the gut feels (e.g. pain). The fact that high levels of stress and anxiety can cause changes in gut motility is no surprise to anyone who has experienced diarrhea before an anxiety-provoking event, like a critical work presentation or school exam.

Depression is a medical illness, and we have growing evidence demonstrating that depression is caused, at least in part, by inflammation. This explains the strong correlation between depression and heart disease, type-2 diabetes, inflammatory bowel disease, rheumatological disorders and other inflammatory illnesses.

It's difficult for patients to accept that their real, severe, disabling pain or other physical symptoms might be due to, or worsened by, mental illness. This is especially difficult for patients to accept if they don't believe that mental illnesses are real, serious, debilitating medical illnesses.

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