What Causes Depression

Dr. Sonya Nobbe, ND

So you’ve been told that you have a deficiency of the “happy” brain chemical serotonin, and that a drug will help you feel better by increasing your body’s response to serotonin. But what caused that serotonin deficiency in the first place? And what will happen if you neglect to address this underlying cause by relying solely on the medication?

Research clearly demonstrates that chronic stress can cause serotonin deficiencies and depression. Many of us would agree that spiritual or emotional stress incurred during childhood or in our jobs and relationships, can lead to depression. But chronic ‘stress’ also applies to physiological (body) stress. Stress from chronic illness can stimulate biochemical processes (e.g. inflammation), in the body that “steal” nutrients otherwise used for serotonin production, thereby contributing to depression symptoms. This stress biochemistry is a survival strategy that our bodies have used theoretically since the caveman age, and we haven’t adapted yet to our fast-paced North American culture.

Our bodies are built to manage short bouts of high stress, such as what you might feel if suddenly attacked by a wild animal. Our bodies are not biochemically equipped to manage any amount of chronic stress, no matter how low grade, and no matter whether emotional, environmental, or physical. When “healthy” biochemical processes are put on hold in favour of those that support our stress response, nutrients are depleted, normal wear and tear on our bodies is not repaired, our bodies switch to inefficient energy production processes (i.e. we feel tired and ‘old’), and chronic disease progresses.

What common health conditions can cause this shift in our body’s biochemistry and drop in serotonin? A surprisingly high number! This list potentially includes anything from food intolerances to blood sugar imbalances, heart disease, arthritis, and insomnia. Research links each one of these conditions to depression symptoms, though why it affects some people and not others is still a medical mystery.

Our serotonin levels are also affected by the health of our digestive tract. Food intolerances and some digestive diseases are known to substantially reduce the gut’s ability to absorb nutrients from food, including the amino acid tryptophan and mineral iron, which our brain uses to make serotonin. Furthermore, up to 95% of the serotonin in our bodies is actually made by cells in our intestine! Unhealthy guts can change serotonin metabolism, thereby affecting our mood.

Estrogen and progesterone hormones also affect our mood by directly targeting serotonin receptors in the brain. Many women (and their partners!) will tell you that their mood is clearly affected at the end of their menstrual cycle when estrogen levels are high relative to progesterone levels. Supporting the body’s ability to create a better hormone balance can dramatically improve mood symptoms due to hormone imbalances.

The cause of mental health concerns rarely exists in the brain. It’s unfortunately not as simple as taking a pill (whether pharmaceutical, botanical, or natural supplement), to re-balance brain chemicals. And though depression is most certainly comprised of varying degrees of emotional and spiritual concerns, there are quite a few common physical health concerns that can directly contribute to depression. Working with a health practitioner to address these physical conditions is critical to the successful treatment of your mood.

brain, Mental health, stress


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