We know that depression is a physical phenomenon. Thanks to modern imaging, we can see it actually taking place, like a tiny squid secreting dark ink in the left prefrontal regions of the brain. We also know that genes are a factor in both depression and bipolar disorder, that in twins there is a co-occurrence that cannot be explained away by chance, and that these conditions often have interlocking family histories spanning several generations.

But life, let alone depression and bipolar disorder, is never that simple.

Yes, our mental well-being is dependent on the brain's 100 billion neurons and how they connect and interact with other neurons, but it takes a push from the outside environment to start the process, creating a stimulus and response relationship that defines who we are. According to the Surgeon General's landmark 1999 Report on Mental Health:

"When a neuron forms a synapse with its target cell, the pattern of activity, usually furnished by external environmental stimulation, strengthens or weakens the developing synapse. Only strengthened synaptic connections survive early development to form enduring connections, while weakened synaptic connections are eliminated ... Later in the course of development, established patterns of connections still can be altered by the environment - through learning."

Depression and Stress

According to the Surgeon General, stressful life events loom large in depression. Thirty to 40 percent of those undergoing divorce report a significant increase in symptoms of depression and anxiety. Single mothers face twice the risk of depression as do married mothers. Victims of domestic violence must often bear their considerable emotional burdens while battling incapacitating depression. At least 10 to 20 percent of widows and widowers develop clinical depression during the first year of bereavement.

In the words of the Surgeon General: "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."

Stress is thought to mobilize the sympathetic nervous system that triggers the fight-or-flight response and a host of physiological reactions. Research in both rodents and primates shows maternal deprivation stresses young animals and may predispose them to a lifetime of overreaction to stress.

Women provide an excellent case study. The Report cites two examples, noting: "Research conducted in working-class neighborhoods suggests that the combination of life stress and inadequate social support contributes to women's greater susceptibility to depressive symptoms."

In a study of Old Order Amish in Pennsylvania, the rate of depression was extremely low, and equivalent for men and women (as opposed to double that of men in the general population). This was enough for the Surgeon General to conclude: "Something about the environment thus appears to interact with a woman's biology to cause a disproportionate incidence of depressive episodes among women."

Depression and Other Outside Factors

But men and women are thinking animals. According to cognitive theories, depression arises from a subjective feeling of helplessness and entrapment. The critical factor is the interpretation of the stressful event rather than the actual event, itself. For example, the Report states, a romantic breakup will trigger a much stronger emotional response if the affected person believes: "I am incomplete and empty without her love," or "I will never find another who makes me feel the way he does."

Adolescent girls suffer from depression in far greater numbers than boys, possibly because they are more socially-oriented and more dependent on positive social relationships. Also, girls may dwell more on negative events than do boys.

Negative thinking in itself may not be sufficient to engender depression, but when a pattern of thinking is embedded in an already mildly-depressed mood, a downward spiral may ensue.

There is uncertainty over whether a negative mindset actually precedes depression or makes its appearance only after a person is depressed, or is a consequence of a previous, perhaps unnoticed, depressive episode. Moreover we have yet another factor at play, here, that of temperament and personality. According to the Report:

"The study of personality and temperament is gaining momentum. Neuroticism predisposes to anxiety and depression. Having an easy-going temperament, on the other hand, protects against depression. Further, those with severe personality disorder are particularly likely to have a history of early adversity or maltreatment."

But whether a shy child, say, remains vulnerable into adulthood also depends on parental influence and life experience, thus completing that neat little circle of upbringing, personal disposition, life history, and stressful events that we refer to collectively as environment.

Lingering Questions

Of course, this leaves begging a basic question: If the environment is so strongly linked to the mental distress of much of the population, shouldn't we be seeking to address some key issues, to right some obvious social wrongs?

If say depression turned out to be the equivalent of black lung disease, wouldn't it make sense find and root out some of the actual causes?

Or have we truly given up on the idea that we can change the world for the better, that we must settle, instead, for our medications and talking therapies? Has Prozac Nation, in effect, replaced equal justice under law?

The Surgeon General, predictably, didn't get into all of that. Thirty or so years ago, back in the sixties, a person in his position might have fired off a few zingers. Then again, thirty years ago the Surgeon General and everyone else all but ignored mental health, so we should probably be grateful for what we have.

In the meantime, knowing how environmentally unfriendly the world actually is - both for the well-off and their less fortunate counterparts - and that it will continue to get worse before it gets better, it pays now more than ever to look after yourself.

For free online issues of McMan's Depression and Bipolar Weekly, email me and put "Sample" in the heading and your email address in the body.

Updated June 14, 2004.

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John McManamy

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