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Depression and Stress

© John McManamy

"Recent stressful events were the most powerful risk factor for an episode of major depression."

Stress - it's there in the environment, from any minor annoyance to an event likely to precipitate a flight-or-fight response to the kind of violation that imprints the mind with severe trauma. It's also there in our biology in the form of hormones that play a key role in mediating our response to the outside world. These same hormones also act as middlemen in a host of co-occurring illnesses.

Each day, we are learning ever more on the relationship between stress and depression, and although there is a lot we still do not know, the presence of stress as a major role-player in the disease process is now considered beyond dispute, with therapies increasingly geared toward neutralizing its vast destructive powers. According to the Surgeon General in his landmark Report on Mental Health:

"The compelling impact of past parental neglect, physical and sexual abuse, and other forms of maltreatment on both adult emotional well-being and brain function is now firmly established for depression."

A study of rhesus monkeys separated from their mothers found higher levels of the stress hormone cortisol, as well as ACTH (adrenocorticotropic hormone), and lower cerebrospinal fluid levels of noradrenaline. Twenty percent of the infants from the same study also reacted negatively to brief separations from their mothers.

ACTH is a hormone that is part of a biological chain of events beginning when the neuropeptide CRF (corticotropin-releasing factor) is produced by the hypothalamus, which activates the pituitary gland to increase the release of ACTH, which then induces the adrenal gland to release more cortisol.

The medical cognoscenti refer to the locus of this activity as the hypothalamic-pituitary-adrenocortical (HPA) axis.

Laboratory animals injected with CRF were found to exhibit symptoms of depression, from weight loss to deceased sexual activity. CRF is found in higher concentrations in the cerebrospinal fluid of depressed patients, who also have are greater numbers of CRF neurons. CRF is also found in areas of the brain, and appears to be hyper-secreted during depression.

In a just-published Emory University study, four groups of women were subjected to the stressful experience of speaking and performing math tests in front of an audience, then blood samples were taken and heart rates measured. The researchers found that the women with a history of childhood abuse and current major depression exhibited a more than six-fold greater ACTH response to stress than those in the control groups.

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