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The Chemical Connection to Depression

Mental health experts believe that depression results from changes in the levels of chemicals in the brain and the body. In the brain, the chemicals are neurotransmitters. In the body, the chemicals are hormones. These chemicals can affect you in many ways, including your energy level, your feelings, your eating habits, and even your sleeping patterns. The change in the level of chemicals is probably a combination of your biology, heredity, personality, thinking patterns, environment, and other factors.

Brain Chemicals

Depression is a disorder of the brain. Researchers in the area of mood disorders believe that chemicals called neurotransmitters are involved in depression. Nerve impulses cause the release of chemicals from one nerve cell, or neuron, to the next, allowing cells to communicate with one another. Too little or too much of these important neurotransmitters may be released and cause or contribute to depression. Some of the neurotransmitters believed to be linked to depression are serotonin , norepinephrine, and dopamine.


Other chemicals called hormones may affect the delicate balance of chemicals in the brain. The potential relationship between depression and hormones focuses on 3 main areas: the fight-or-flight response, the thyroid hormones, and the sex hormones.

  • Frequently activated fight-or-flight response. Your body's hormone system regulates your response to stress. When you're under stress or perceive a threat, your hypothalamus - the area of the brain that regulates the release of hormones from glands throughout your body - increases production of a substance called corticotropin releasing factor, or CRF. CRF causes the pituitary and adrenal glands to increase the secretion of hormones that cause the body to be on alert and ready to defend itself. That means your muscles tense, your breathing becomes shallow, and your senses become sharper. Studies have shown that when this often-called fight-or-flight stress response is activated frequently, it may lead to depression. Experts have found that the hormone system is often overactive in many depressed people and that antidepressant medications can reduce CRF levels.
  • Over - or understimulation of thyroid hormones. The thyroid gland produces important hormones that can affect depression. An overactive thyroid, a condition called hyperthyroidism, can cause overproduction of hormones and result in symptoms such as anxiety, nervousness, and insomnia. An underactive thyroid, a condition called hypothyroidism, can cause depression and result in fatigue, mental slowness, and other symptoms.
  • Sex hormones. Sex hormones, especially female hormones, may be associated with depression. Childbirth, the menstrual period, and menopause all cause hormonal changes that may be linked to depression. Depression among women increases during times of hormonal change, such as after childbirth. Research suggests that 4 out of 10 women experience mood changes before their menstrual cycle. Approximately 5% of women experience serious depression during premenstrual periods. Talk with your healthcare provider if you feel depressed around your period, during pregnancy, after childbirth, or around the time of menopause. Also let your healthcare provider know if you feel depressed after starting hormone medications such as birth control pills or hormone replacement therapy.