Lately I’ve been reading Peter Cramer’s book Against Depression, which is his follow-up to Listening to Prozac, his groundbreaking book about depression and Prozac. This is a fascinating book, as good as Listening to Prozac. If you have any interest at all in learning more about depression, I would strongly recommend this book, which is a philosophical and scientific exploration of depression. Much of what follows is inspired by this book.

Today I want to talk about the new and exciting research on depression done by Kenneth Kendler at the Virginia Commonwealth University.

Dr. Kendler has looked at the causes of major depression. His research finds that there are three pathways to depression. That means there are a number of different triggers that cause people to become depressed.

The first is what he calls the internal pathway. This includes two variables that predict depression–childhood onset anxiety disorders (before age 18) and neuroticism (a general trait of psychological disorder). This means that if you have an anxiety disorder as a child, or if you are generally neurotic, you are more likely to become depressed later in life.

The second is the external pathway. This path includes two variables: conduct disorder and substance abuse. (Conduct disorder means getting into trouble with the law.) So if you abused alcohol as a teenager, and got arrested, you are more likely to get depressed later in life.

The third path is not surprisingly, through adversity in life. And this pathway is the most complex. It starts in childhood with a disturbed family environment, childhood sexual abuse, and the loss of a parent. It continues with low educational achievement, lifetime trauma, low social support, and the likelihood of divorce. Finally, it ends with current stressors such as marital problems, life difficulties, and stressful events in the last year before depression starts. Kendler believes that much of the adversity that people experience are actually interpersonal difficulties.

What is worse is that the factors are related to one another. If you have adversity in childhood, you are more likely to develop conduct disorder and substance abuse, and these disorders make it more likely you will get into a bad marriage, lose your job, etc.

This complex model was able to account for 52 percent of the likelihood of depression in a one year period.

So far none of this is really that surprising or interesting. After all, most people would predict that a lousy childhood, getting into trouble, and being anxious might lead to depression.

The really interesting part of his research is how these factors influence one another, and how the genetic component influences all of them. Genetic factors influence all three of the major factors. If you are genetically prone to depression, you are more likely to have a lousy childhood, get into trouble and abuse substances, and be anxious and neurotic! How does this work?

Kendler isn’t sure, but suspects that if you are prone to depression, your parents might have been also, and this impaired their ability to parent well. Or perhaps, it is harder to parent an anxious, depressed, neurotic child. Or perhaps both are true; depressed parents have a harder time parenting, and their children tend to be moodier and harder to deal with. The genetic propensity to depression may also be connected to substance abuse directly or as an attempt to self-medicate the depression.

Other findings from his research. He found that if you have an anxiety disorder before age 18, this is a strong and independent predictor of depression.

So what can we learn from this research?

There appears to be a tragic path to depression. The depressed person is born with a genetic tendency to depression which in turn is correlated with the likelihood of a bad childhood. Then they do worse in school, get in trouble more, turn to substance abuse, and then aas adults pick bad relationships, have more conflict in jobs and family, and are more likely to be traumatized. Basically their whole life goes poorly. Chaos and conflict and loss and low social support leads to depression. A single depression leads to future depressions.

It is all pretty depressing! But what it shows is also the pathway to healing. For instance, therapy in childhood may help prevent some of this. Treating early anxiety disorders or substance abuse may prevent some of the later chaos.

It also shows why therapy is so important in the treatment of adult depression. Although anti-depressant medications may help with the biological problems in depression, therapy is necessary to help clients learn new ways to relate to people and how to make better interpersonal decisions. A supportive therapist may also help buffer the effects of adversity and loss and make depression a less likely outcome.

This research also suggests that depression is not just a mood state, but is an illness that affects many aspects of a person’s life (and in a negative direction.) We need to be aggressive in treating this serious and debilitating illness.

Copyright 2006 The Psychology Lounge/TPL Productions