It is almost a cliché to say that we are social animals. But the fact that we are has very deep implications for both our biology and our psychology.

We are born utterly dependent; from the moment we pop out, a social relationship becomes essential to living, namely the relationship with our mother (as well as other family members). Through that dependency—for physical survival and mental, social, physical, and sensory stimulation—we form connections with other people who become significant in shaping our view of ourselves and of the world around us. That socialization process also structures the brain in important and enduring ways. Through the complex processes of socialization, families can create in their members, and especially in their children, either susceptibility or resistance to depression that can last a lifetime.

The notion that depression can be spread strictly by social means as a social contagion is supported by a great deal of evidence. For example, there is now neurological evidence that the apathy and withdrawal of mothers who have postpartum depression show up in the baby's brain as an underdeveloped emotional region. Such mothers are constricted in their emotional displays and do not engage with the baby the way nondepressed mothers do—talking in a singsong voice, playing games, stimulating the baby. That deficit in the brain, along with other related risk factors, dramatically increases the likelihood that the child, too, will become depressed.

Epidemiologic evidence also points to the major role of contagion factors in depression. The rate and nature of depression vary dramatically from culture to culture—unlike with schizophrenia, where roughly 1 percent of the population is affected no matter the culture sampled. The World Health Organization recently declared depression the fourth leading cause of human disability and suffering and predicted that by the year 2020 it will be the second leading cause. That's not biology run amok; it reflects the social spread of the kinds of cultural values and social conditions that give rise to depression.

Further evidence that moods spread through social interaction is found in the social lives of depressed people and their loved ones. The depressed have far more difficulty than the nondepressed in their social experiences. They have more family arguments and more marital arguments. They have less relationship satisfaction and are significantly unhappier. And they deplete everyone around them, spreading social pain and further corroding social relationships in an ongoing vicious cycle.

"It's exhausting," says Sarah Paul, 50, manager of records for an insurance company in Seattle. "My husband is depressed much of the time. He can suck the joy out of things faster than anyone I've known. It's hard on me because I feel like I can't talk about negative things very often; he's already so down. It's so frustrating I also deal with depression."

Paul voices concern for their 6-year-old daughter. "I worry how she is going to turn out with two depressed parents. I grew up that way, and I think that's why I'm with my husband. When I was single, my number one desire was to find someone positive. But I married someone negative because the discomfort is comfortable; I know what to do. I'm concerned about what I'm modeling; I don't want my daughter to continue the cycle."

Long-term epidemiologic studies show that depression intensifies from one generation to the next. Today's parents represent the largest group of depression sufferers raising the fastest-growing group of depression sufferers. We are on average four times more depressed than our parents and ten times more than our grandparents. This is not just a reflection of greater awareness of the disorder.

Depression is a disorder with many facets. There is a genetic vulnerability, although it is turning out to be smaller than many scientists thought. The larger contribution comes from the ways we learn to regulate our own internal experience, which includes our explanatory style (the meaning we attach to life experiences), our cognitive style (how we think and use information), our coping style (how we manage stress and adversity) , our problem-solving style, and our relational style.

All of these are acquired through socialization forces in the family, the modeling and transmission of enduring patterns of thinking, feeling, and relating to others. We learn to think and to interpret and respond to events through the cumulative effect of our socialization—the kinds of parenting received, the kinds of explanations offered, the influence of family members, the teachings of others.

There is a near-perfect correlation between a parent's explanatory style and a child's. Every time a child asks, "Why, Mommy?" or "Why, Daddy?" the explanation provided invariably embodies a particular style of thinking and attributions of causality. Each question is a vehicle for the transmission of thinking that interprets events in a way that is congruent with external reality or that reflects more subjective or hyperemotional responses.

"Why didn't Uncle Bob come to the picnic, Mom?" There's a world of difference between "He must be mad at me" and " I don't know, the next time we talk to Uncle Bob let's ask him." There are also the kinds of attributions that reflect a permanently negative perspective: "Mom, I tried to do this and couldn't, would you help me do it?" "No, you'll never be able to do it, it's too hard."

Such mundane interactions happen many times a day over years, and they invisibly shape people's perspectives about themselves and the world around them. Their deeply ingrained perceptions influence how they filter experience, whether they are willing to try something new, whether they'll reflexively blame themselves or others if something doesn't work out well, whether they need to be perfect, whether they'll even bother to try to do something even though they'll never be able to do it perfectly. What patterns the family intentionally or unintentionally encourages in its members influence vulnerability to depression.

Sarah Paul remembers not even being able to ask "why" in her family. "It was regarded as implicit criticism of the way things were being done." One result, she says, is growing up unable to see other options beyond her first (negative) reaction to the situation she faced. "I didn't know there were other ways to be. I was locked into seeing the world one way."

Depressed people often globally assume things are out of their control, which fuels their sense of helplessness and hopelessness. Consider the kind of talk that takes place at the dinner table, an important node in the social transmission of depression. When asked how your day was, if you say "good" and leave it at that, you're delivering a global response. This overgeneral style of thinking supports depression because it leads people to say things like, "All I want is to be happy" or "All I want is to have a good relationship"; they don't know how to develop a specific, realistic strategy to be happy or to have a good relationship.

Anything that victimizes someone holds the potential to depress that person. Others may victimize us if we let them, but what victimizes us the most is telling ourselves what we can't do, what we're inept at, what we're not good enough to do—all those things by which we limit and even devalue ourselves. "My husband doesn't see a loving god," says Paul. "His view is not exactly paranoid, but distrustful. He doesn't see a friendly world; therefore he doesn't get one. He sees himself as a victim who has no choices. He doesn't feel like he has much power in his life. He owns a small business he hates and feels trapped in it. He has always had a dream of owning a movie theater. But his sense of hopelessness always provides him with reasons why it wouldn't work. So he never does anything to further his dream."

"When I was little, I thought it was normal to have a mother who cried to herself on the floor of her room on a daily basis," reports Katie West, a life coach in Portland, Maine, whose early experience inspired her work path. "Only in college—in a course in children's literature—did I learn the term 'depression' and think, 'That's what my mom has.'" Ultimately her mother was hospitalized and diagnosed with severe depression—a relief "because it had always been ignored and often passed off as my problem."

Parental depression can be insidious, West notes, "because the depressive voice can masquerade as realism. There's lots of fear driving depression, and so there can be lots of protectiveness." Her mother, she recalls, would typically issue a discouraging "that's not possible" to young Katie's requests.

Although it may seem to, depression doesn't usually strike out of the blue. The average age at onset is in the mid-20s. (Not long ago , it was mid-30s, another factor pointing to social contagion.) But by the time a person becomes depressed, the risk factors have typically been in place for years. Statistically, most who suffer from depression also suffer a coexisting, or comorbid, condition, the most common of which is some form of anxiety disorder. However, the two conditions do not manifest at the same time; anxiety precedes depression by years. A child who is diagnosably anxious at age 8 or 9 is at high risk for becoming a depressed adult, which, to the aware adult, presents an opportunity for preventive intervention. Close examination is likely to reveal that such a child does not deal well with ambiguity because he or she sees danger in ambiguous situations; the child has a negative interpretive style.

Studies show that such a pattern in interpreting experience is established early in life. In one study, children 8 years old were asked how they would respond if they were out shopping with their mother in a crowded department store 30 miles from home and suddenly found themselves separated from their parent. The anxious children generated scary scenarios of never seeing their parents again and being adopted into families of strangers. But the nonanxious kids said they'd simply go to the store manager and ask that an announcement be made on the public address system. In short, free of inner emotional turmoil, they could focus on and think their way through to solving the problem.

Clearly, another avenue of depression contagion in families is the failure to teach children specific coping skills to manage adversity. What's more, exposure to interpretive styles that overgeneralize negative experience typically renders children hyperemotional in the face of difficulty and thus unable to solve any problem they are up against. Parents can encourage children to be problem-solvers by good-naturedly asking them during various activities how they would handle contingencies that arise. ("What do you think you might do if Billy doesn't call you back?") The idea is to anticipate not only what might go wrong but how to sensibly correct it. Asking "What if?" is a good habit to encourage for general mental health. Depressed and anxious people are unable to think past the hazard, and then they panic.

Depression is a disorder rooted in subjectivity. The depressed overly focus internally on their thoughts, their feelings, their subjective way of experiencing themselves in life. They are notoriously bad at engaging in reality testing, gathering information, and double-checking whether their thoughts or feelings actually make sense in the circumstances. This internal orientation can become so pervasive that it leads directly to an inability to relate well to others; it's difficult to have empathy or concern for others when what matters most to you is how you feel. Likewise, it's hard to be open to others' perspectives when you defend your right to overreact or misinterpret things by saying, "But that's how I feel!" This is one of the unfortunate patterns that serves only to drive others away.

A family environment of perfectionism reflecting unrealistically high standards is another factor that greatly increases vulnerability to depression. Imagine a child comes home with a 95 on a test and is sternly asked, "How come you missed 5 points?" Such interactions feed the destructive idea that you're not good enough and no matter what you do, you'll never be good enough. Perfectionism creates a harsh internal environment , and it fails to teach people how to accept inevitable limitations.

Another important element of socialization that operates in families (and other groups) is whether emotions can be expressed or not, what kinds of emotions can be expressed, and to what degree. Children learn quickly from the affective displays within a family or community what will be tolerated and what will not. Many families, for example, prohibit expressions of anger and so teach their children to suppress the emotion. Being devalued with no means of expression modeled, anger can too easily become explosive, a common theme in depressed relationships.

The havoc depression wreaks in the social milieu of families is not limited to what transpires in parent-child relationships. It also affects the marriage. Depression influences how able intimate partners are to support each other and how much conflict there is in their relationship. It affects the ability to solve problems as a couple and to deal effectively as partners with parenting issues and discipline.

It affects the sexual relationship and how much closeness there is between partners. And it affects their social life with others. At the very least, depression is an extra stressor that partners have to deal with in a relationship. No less than 50 percent of the depressed who are married (or have an intimate partner) experience relationship distress as a direct consequence of the depression in one or both partners. And of the people who present for couples therapy, there's a 50 percent chance that at least one of the partners has diagnosable depression.

Many divorces occur directly as a result of undiagnosed depression. If I'm depressed and I have an attributional style that leads me to blame others, I'll insist you're the reason I'm unhappy, and I've got to get away from you. But you're not the problem; my depression is really the problem. When a husband is depressed, the wife is more likely to blame herself for his unhappiness and their marital troubles. But when the wife is depressed, her husband is apt to think she's the source of their problems.

If victimization is a recipe for depression, the way many people victimize themselves is by getting into destructive relationships or not knowing how to establish and maintain good relationships. They don't know how to set and keep clear boundaries about each other's emotions or how to deal with each other in respectful ways when the going gets tough. They don't know how to skillfully negotiate conflicts or self-correct when things go wrong. What once felt like a happy relationship becomes a source of disappointment, distress, pain, rejection, and humiliation.

Unfortunately, depression robs people of the ability to recognize others as sources of comfort. And indeed, depression spreads socially in yet another way: The depressed drain others and make it difficult for even the best-intentioned to be around them. They engage in patterns of behavior such as constant complaining or excessive reassurance-seeking, as in frequently asking, "Am I OK?" That gets really old really fast.

Sadly, depression encourages those in its grip to isolate themselves socially. It is part of the pervasive negativity of depression that they restrict themselves from the things that could make them feel good. Your spouse says, let's go to a movie or out to eat or over to see the Smiths; you say, no, I'm too depressed. The depressed make their world smaller and smaller until the depression becomes the centerpiece of their life. Building regular opportunities for fun as well as personal growth into your life can make a huge difference in your mood.

Everybody is vulnerable to depression to some degree. As long as you are capable of having a mood, you're capable of having a mood issue. You need to assume responsibility for managing your moods the same way you manage your physical body. It's an ongoing task, much like managing your checking account or your child; you can't make a deposit once and be done with money. You can't discipline your kid once and be done with parenting.

As you learn your vulnerabilities in thinking and behavioral style, you can make good decisions on how to manage your mood and how to operate preventively.

Doreen Orion is a psychiatrist in Boulder, Colorado, who grew up with two depressed parents. Both were college professors, and she was an only child. "No surprise I went into a helping profession," she reports. "I grew up feeling inadequate, that if I were only better, they would be, too. In addition, I married what was familiar for my first marriage. Through my own growth process and professional training, I realized that staying in that marriage would mean duplicating what my parents had, so we divorced." It ended the cycle.

She is "now happily married to a non-depressed guy and, unlike my parents, we are not feeling trapped in our lives. On the contrary, we are selling our home so we can semi-retire (at age 50) to live in our RV."

Orion and her husband already took a year off to travel the country in their custom-outfitted bus. She has written a book about the experience, Queen of the Road, and spends time every week talking to book clubs all over the country. "It's fun, interesting, and different for me, because it takes me away from what I'm familiar with in my upbringing. My dad is rather antisocial; he does not like to go out or talk to people, which I'm sure only adds to his feeling depressed. I was a pretty shy, quiet kid, so 'meeting' all these people is more reinforcement that I'm doing things differently and inoculating myself."

Katie West, equally inspired by her experience growing up, has also found a way of doing things differently. She describes herself as not just a life coach but a levity coach. "I target areas where people need laughter. I've come to see that the way in life is not through—it's up. My job is to make people feel more buoyant, more hopeful."

It is possible to make people less susceptible to depression by teaching children social and cognitive skills. But there's growing evidence that social skills are deteriorating and that people are less available and less deliberate about building quality relationships. Studies show that young people are becoming more impulsive, more aggressive, more narcissistic, more self-absorbed. The more self-absorbed people are, the more negative feedback they absorb from others, the worse they feel, and the less skilled they are in building relationships.

Despite the huge role that social factors play in depression, the disorder tends to be addressed only one-dimensionally—physiologically, with medication. Antidepressants, now the most widely prescribed drugs in America, may be part of the solution, but they are not the whole solution. No type or amount of medication will build you a support network or make you more socially skilled. Good relationships are essential to establishing, maintaining, and restoring mental health. Unless we recognize and address the critical role of social factors in depression, we will never get the disorder to release its stranglehold on us.