Causes of Depression

Studies consistently show that depression is most associated with the number of stressors experienced in life, and the effect is cumulative—the more stresses that accrue over time, the greater the likelihood of getting depressed. The loss of an important relationship by death or divorce is experienced by most people as a major stress requiring significant adjustment.

Loneliness is both a physical and emotional stressor, and rates of loneliness, known to be high among the elderly, are sharply rising among the young, who increasingly report having no close friends. Job loss or the threat of job loss are almost invariably sources of constant worry. In the absence of a wide array of coping skills, even minor bumps on life’s journey can become significant stressors.

Although depression most often arises in response to some kind of defeat, depression can seem to arise out of the blue, for no obvious reason. It may even arise when life appears to be going extremely well. What is often hidden from conscious awareness are basic beliefs about life and love and work, or ways of explaining life’s twists and turns, many of which are learned at home in the early years of life.

Additionally, people may reach goals they’ve pursued for a long time, and find that they don’t deliver the emotional rewards they secretly or openly expected. In such cases, people may feel they don’t have the right to be depressed and may even feel ashamed of being depressed. Cognitive behavioral therapy is highly effective at unearthing and correcting such problematic views.

Studies show that one factor consistently associated with depression is the number and degree of major stresses experienced in life. Poverty, for example, is a significant, enduring stressor, not easily modifiable, highly linked to depression risk. But to a degree still under study, attitude plays a major role in the perception of stress.

Some stress is necessary to keep people alert. It isn’t just that situations differ in the degree to which they stress human systems; much depends on how people regard some situations—say, taking final exams. People who see stress as a challenge rather than as a plague recruit positive rather than negative emotions. What’s more, they do not experience the harmful effects of stress hormones on body and brain.

Brooding over mistakes or unpleasant experiences, jumping to catastrophic conclusions from one or two setbacks, overgeneralizing from limited evidence—all are errors of thinking, or cognitive distortions, strongly linked to depression.

Such thinking mires the brain in negativity and, if unchecked, breed self-doubt and hopelessness. What’s more, studies show that negative thinking styles such as catastrophizing actually change physiology. Researchers have found that they enhance reactivity to painful stimulation and raise levels of the stress hormone cortisol and of pro-inflammatory agents in the blood. The inflammatory response brings on behavioral changes commonly associated with both sickness and depression—fatigue, slow reaction time, cognitive sluggishness, and loss of appetite.

Research documents that there is a strong relationship between adverse experience in childhood—such as verbal or physical abuse or household dysfunction caused by a mentally ill parent—and the lifetime risk of depression. Studies show that verbal abuse more than doubles the lifetime risk of depression. Adverse experiences are a significant source of stress.

But whether they summon resources for successful coping or lead to despair depends in part on the situation and in part on the person. A child facing verbally or physically abusive treatment at home or school who has no means of escaping continuing injury is at elevated risk for developing depression. Situations may not be subject to change—but attitudes, interpretation, and meaning of experience are always under individual control and can confer resistance to depression and other disorders..

Perfectionism is like an endless negative report card. Those in its grip don’t just hold high standards for themselves, they are perpetual self-critics, always judging themselves harshly. They focus on the very thing they most want to avoid—negative evaluation and failure. Perfectionism keeps people completely self-absorbed, always finding fault with themselves, a mindset that prevents them from taking on potentially-rewarding challenges.

Even when perfectionists complete a task, they cannot enjoy a sense of achievement; relentless concern with mistakes leads them to be haunted with uncertainty about their performance. The constant negative focus leads to a negatively distorted view of themselves, self-doubt, and feelings of inadequacy and worthlessness. Perfectionists are vulnerable to depression because their self-worth is contingent on fully achieving goals—a condition that, by definition, they can never meet.

Learned helplessness is a state of mind in which people come to believe (often through experiences of childhood abuse or neglect) that they have no way of escaping difficult or painful circumstances and therefore exert no effort to change distressing situations even when it is possible to do so. The resulting passivity can keep people from taking any measures to avoid a problem or to help themselves when one arises, or to seek help from others, compounding their own suffering and precipitating such feelings as hopelessness that are the hallmarks of depression. Because the helplessness is learned, the belief that no action matters can be unlearned; part of the cure is also gaining a realistic understanding of what can and can’t be controlled in life.

There is growing evidence that depression gives rise to inflammation and the inflammatory response creates or exacerbates depression. Neuroscientists know that there is lots of crosstalk in the brain between neural circuits and inflammatory pathways. Negative thoughts are a source of psychological pain.

Like all signs of injury, pain mobilizes various immune cells to help subdue the source, and that mobilization creates inflammation. Stress is known to activate an inflammatory response. The presence of inflammatory cells in the brain may be one reason many drug treatments for depression fail; they do not target inflammation.

Loneliness assaults the body and mind in multiple ways. By itself, it is felt as a major stress, and is linked to the release of stress hormones, which are known to impair such brain operations as learning and memory retrieval. What’s more, loneliness magnifies the perception of all other stresses. It diminishes functioning of the immune system and readily leads to inflammation, a known pathway to depression.

The emotional discomfort of loneliness makes us feel sad, and sadness saps our energy and slows functioning of all body systems. Companionship is such a powerful buffer to all human difficulty that loneliness is said to have even more of a detrimental effect on health than cigarette smoking.

Many people believe that depression is caused by a “chemical imbalance” in the brain. Experts explain that depression is far more complex and that it is unproductive to think of depression as a brain disease that is primarily biological.

Instead, depression can be viewed as a behavioral shutdown in response to overwhelmingly negative situations in which you have little personal control, lack resources for dealing with them, and have little comfort in the way of social support. The response is reflected in many operations of the brain, such as difficulty with memory, sluggishness of thinking, inability to feel pleasure, loss of appetite and interest in sex, and heightened perception of pain.

Neuroimaging studies indeed show changes in brain function among depressed people, and they are generally associated with impairments of connectivity among brain areas that normally work together. Studies also show that such changes are reversible as depression lifts.

While genetics is believed to confer some susceptibility, there is no single gene or set of genes implicated; so far, it appears that a very large number of genes—likely modifiable by diet or behavior—each contributes a very tiny degree of vulnerability that could precipitate depression under conditions of stress. People can also be at risk of depression because of their personality attributes, particularly if they have a tendency to worry a lot, have low self-esteem, are perfectionists, are sensitive to personal criticism, or are self-critical and negative. Of the Big Five personality dimensions, the one most consistently associated with depression susceptibility is the trait of neuroticism. It denotes the degree to which the negative affect system is readily activated. People high in trait neuroticism are inclined to find experiences distressing, to worry, and to doubt themselves disproportionate to the circumstances they are in. In addition, studies indicate that women are at especially high risk for depression after divorce and men are at high risk following following financial, occupational, or legal problems.

Depression can be transmitted in families in several ways. Parents and children may share an array of genes that create susceptibility to depression. Even more subtly, parents may engage in depressive thinking and explanatory styles that children acquire unwittingly in the air they breathe every day at home while growing up.

There is considerable evidence that when mothers of young children are depressed, they fail to engage with their children. As a result, babies do not acquire the strong emotional bond that enables them to grow, to withstand stress, to develop emotional regulation, and to become responsive to others. Treating depressed mothers is often the best way to treat problems in children.

Depression and anxiety are considered two faces of the same coin. Both involve brooding over experience—in depression, things that happened in the past; in anxiety, things that might happen in the future. Depression is also thought to result from sustained anxiety. More than half of all people with major depression also suffer from persistent anxiety. The two conditions share many symptoms, including insomnia, difficulty concentrating, negative thinking, and loss of appetite. Many treatments that relieve depression also relieve anxiety.

Depression rates are rising especially among the young. While the lifetime risk of depression is approximately 20 percent, for the general population the highest rates currently occur among young adults, those between the ages of 18 and 29, while individuals over 65 have the lowest rates.

Experts cite several reasons why the young are especially susceptible. They range from social factors, such as decreasing availability of meaningful work, to individual factors, such as lack of coping skills due to overprotective parenting. Cultural factors figure in, too. An increased concern with safety and decreased tolerance for risk has curtailed the opportunities children have for free play, in which children experience joy, gain friends and learn social skills, and discover how to exercise control over their own life.

Around the world, women are 1.7 times more likely to develop depression than are men, and the difference in susceptibility emerges in adolescence. Among younger women, the gender gap in depression is even greater, although before puberty, males and females have equal rates of depression. Studies pinpoint social and cultural reasons as well as biological ones.

Women more often experience internalizing symptoms, reflected in physical pain and other somatic complaints, social withdrawal, and self-blame, while men present with externalizing behaviors, reflected in irritability, anger, aggression, and substance use. In addition, childbirth is associated with a particular form of depression; susceptibility is thought to be related in part to the rapid hormonal shifts that occur postpartum in combination with the vastly increased demands of new motherhood.