Most of us will have some direct or indirect experience with depression. In the past year, have you at some time “felt so depressed that it was difficult to function”? If so, you were not alone. In one national survey, 31 percent of American college students answered Yes (ACHA, 2009).

The college years are an exciting time, but they can also be stressful. Perhaps you wanted to attend college right out of high school but couldn’t afford it, and now you are struggling to find time for school amid family and work responsibilities. Perhaps social stresses—such as missing a partner after a breakup or being excluded from a popular group—have left you feeling isolated or down about your future, or about life in general. You may lack the energy to get things done or even to force yourself out of bed. You may be unable to concentrate, eat, or sleep normally. Occasionally, you may even wonder if you would be better off dead.

Some people’s depression has a seasonal pattern. It regularly returns each fall or winter and departs each spring. For many others, winter darkness simply means more blue moods. When asked “Have you cried today?,” Americans have said Yes more often in the winter.

Depression makes sense from an evolutionary perspective. To feel bad in reaction to very sad events is to be in touch with reality. At such times, depression is like a car’s low-fuel light—a warning signal that we should stop and take appropriate measures. Biologically speaking, life’s purpose is survival and reproduction, not happiness. Just as coughing, vomiting, and various forms of pain protect our body from dangerous toxins, so depression protects us. It slows us down and gives us time to think hard and consider our options (Wrosch & Miller, 2009). It defuses aggression, cuts back on risk taking, and focuses our mind (Allen & Badcock, 2003; Andrews & Thomson, 2009a). As one social psychologist warned, “If someone offered you a pill that would make you permanently happy, you would be well advised to run fast and run far. Emotion is a compass that tells us what to do, and a compass that is perpetually stuck on NORTH is worthless” (Gilbert, 2006).

There is sense to suffering. After reassessing our life, we may redirect our energy in more promising ways. Even mild sadness helps people process and recall faces more accurately (Hills et al., 2011). They also tend to pay more attention to details and make better decisions (Forgas, 2009).

Sometimes, however, depression becomes seriously maladaptive. Abnormal depression can take many forms. Let’s look more closely at two of them—major depressive disorder, a prolonged state of hopeless depression, and bipolar disorder, alternating states of depression and overexcited hyperactivity.

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Joy, contentment, sadness, and despair are different points on a continuum, points at which any of us may be found at any given moment. The difference between a blue mood after bad news and major depressive disorder is like the difference between gasping for breath after a hard run and having chronic asthma. Major depressive disorder occurs when at least five signs of depression last two or more weeks (TABLE 13.6). To sense what major depressive disorder feels like, imagine combining the anguish of grief with the exhaustion you feel after pulling an all-nighter.

Although phobias are more common, depression is the number-one reason people seek mental health services. In the United States, 7.6 percent of people interviewed were experiencing moderate or severe depression (CDC, 2014a). Worldwide, depression trails only low back pain as the leading cause of disability (Global Burden of Disease Study, 2015).

Adults diagnosed with persistent depressive disorder (formerly called dysthymia) have experienced a mildly depressed mood for at least two years (American Psychiatric Association, 2013). They also display at least two of depression’s symptoms.

Our genes dispose some of us, more than others, to respond emotionally to good and bad events (Whisman et al., 2014). In bipolar disorder, people bounce from one emotional extreme to the other (week to week, rather than day to day or moment to moment). When a depressive episode ends, a euphoric, overly talkative, wildly energetic, and extremely optimistic state called mania follows. But before long, the mood either returns to normal or plunges again into depression.

If depression is living in slow motion, mania is fast forward. During mania, people feel little need for sleep, are easily irritated, and show fewer sexual inhibitions. Feeling extreme optimism and self-esteem, they find advice annoying. Yet they need protection from their poor judgment, which may lead to reckless spending or unsafe sex. Thinking fast feels good, but it also increases risk taking (Chandler & Pronin, 2012; Pronin, 2013).

In milder forms, mania’s energy and flood of ideas can fuel creativity. Classical composer George Frideric Handel (1685–1759), who many believe suffered a mild form of bipolar disorder, composed his nearly four-hour-long Messiah during three weeks of intense, creative energy (Keynes, 1980). Bipolar disorder strikes more often among people who rely on emotional expression and vivid imagery, such as poets and artists, and less often among those who rely on precision and logic, such as architects, designers, and journalists (Jamison, 1993, 1995; Kaufman & Baer, 2002; Ludwig, 1995).

Bipolar disorder is much less common than major depressive disorder, but is often more dysfunctional. It afflicts as many men as women. The diagnosis has risen among adolescents, whose mood swings, sometimes prolonged, range from rage to giddiness. In the decade between 1994 and 2003, bipolar diagnoses in under-20 people showed an astonishing 40-fold increase—from an estimated 20,000 to 800,000 (Carey, 2007; Flora & Bobby, 2008; Moreno et al., 2007). The DSM-5 classifications will likely reduce the number of child and adolescent bipolar diagnoses. Some of those who are persistently irritable and who have frequent and recurring behavior outbursts will now instead be diagnosed with disruptive mood dysregulation disorder (Miller, 2010).

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From thousands of studies of the causes, treatment, and prevention of major depressive disorder and bipolar disorder, researchers have pulled out some common threads. Here, we focus primarily on major depressive disorder. Any theory of depression must explain a number of findings (Lewinsohn et al., 1985, 1998, 2003).

Armed with facts, today’s researchers propose biological and cognitive explanations of depression, often combined in a biopsychosocial perspective.

Biological Influences

Depression is a whole-body disorder. It involves genetic predispositions and biochemical imbalances, as well as negative thoughts and a dark mood.

GENES AND DEPRESSION Major depressive disorder and bipolar disorder run in families. The risk of being diagnosed with one of these disorders increases if your parent or sibling has the disorder (Sullivan et al., 2000). If one identical twin is diagnosed with major depressive disorder, the chances are about 1 in 2 that at some time the other twin will be, too. If one identical twin has bipolar disorder, the chances of a similar diagnosis for the co-twin are even higher—7 in 10—even for those twins raised apart (DiLalla et al., 1996). Among fraternal twins, the corresponding odds are just under 2 in 10 (Tsuang & Faraone, 1990). Summarizing the major twin studies (see FIGURE 13.9), one research team estimated the heritability of major depressive disorder—the extent to which individual depression differences are attributable to genes—at 37 percent (Bienvenu et al., 2011).

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To tease out the genes that put people at risk for depression, some researchers have turned to linkage analysis. After finding families in which the disorder appears across several generations, geneticists examine DNA from affected and unaffected family members, looking for differences. Linkage analysis points us to a chromosome neighborhood, note researchers; “a house-to-house search is then needed to find the culprit gene” (Plomin & McGuffin, 2003). But depression is a complex condition. Many genes work together, producing a mosaic of small effects that interact with other factors to put some people at greater risk. If the culprit gene variations can be identified, they may open the door to more effective drug therapy.

THE DEPRESSED BRAIN Scanning devices let us eavesdrop on the brain’s activity. During depression, brain activity slows. During mania, it increases (FIGURE 13.10). Depression can cause the brain’s reward centers to become less active (Miller et al., 2015; Stringaris et al., 2015). During positive emotions, reward centers become more active (Davidson et al., 2002; Heller et al., 2009; Robinson et al., 2012).

At least two neurotransmitter systems are at work during these periods of brain inactivity and hyperactivity. Norepinephrine increases arousal and boosts mood. It is scarce during depression and overabundant during mania. Serotonin is also scarce or inactive during depression (Carver et al., 2008).

In Chapter 14, we will see how drugs that relieve depression tend to make more norepinephrine or serotonin available to the depressed brain. Repetitive physical exercise, such as jogging, which increases serotonin, can have a similar effect (Ilardi, 2009; Jacobs, 1994). To run away from a bad mood, you can sometimes use your own two feet.

Psychological and Social Influences

Biological influences contribute to depression, but as we have so often seen, nature and nurture interact. Our life experiences—diet, drugs, stress, and other environmental influences—can place molecular tags on our chromosomes. These epigenetic changes do not alter our DNA, but they can trigger our genes to turn on or off. Animal studies suggest that long-lasting epigenetic influences may play a role in depression (Nestler, 2011).

Thinking matters, too. The social-cognitive perspective explores how people’s assumptions and expectations influence what they perceive. Many depressed people see life through dark glasses of low self-esteem (Orth et al., 2016). They have intensely negative views of themselves, their situation, and their future. Listen to Norman, a college professor, recalling his depression (Endler, 1982, pp. 45–49):

I [despaired] of ever being human again. I honestly felt subhuman, lower than the lowest vermin. Furthermore, I . . . could not understand why anyone would want to associate with me, let alone love me. . . . I was positive that I was a fraud and a phony and that I didn’t deserve my Ph.D. . . . I didn’t deserve the research grants I had been awarded; I couldn’t understand how I had written books and journal articles. . . . I must have conned a lot of people.

Expecting the worst, depressed people magnify bad experiences and minimize good ones (Wenze et al., 2012). Their self-defeating beliefs and negative explanatory style feed their depression.

NEGATIVE THOUGHTS AND NEGATIVE MOODS INTERACT Self-defeating beliefs may arise from learned helplessness. As we saw in Chapter 10, both dogs and humans act depressed, passive, and withdrawn after experiencing uncontrollable painful events. Learned helplessness is more common in women, who may respond more strongly to stress (Hankin & Abramson, 2001; Mazure et al., 2002; Nolen-Hoeksema, 2001, 2003). Do you agree or disagree with the statement, “I feel frequently overwhelmed by all I have to do”? In a survey of students entering American colleges, 38 percent of the women agreed (Pryor et al., 2006). Only 17 percent of the men agreed. (Did your answer fit that pattern?)

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Why are women nearly twice as vulnerable to depression (Kessler, 2001)? This higher risk may relate to women’s tendency to ruminate—to overthink, fret, or brood (Nolen-Hoeksema, 2003). Rumination can be adaptive. Thanks to the continuous firing of an attention-sustaining area of the brain, it can help us focus intently on a problem (Altamirano et al., 2010; Andrews & Thomson, 2009a,b). But relentless, self-focused rumination is not adaptive. It diverts us from thinking about other life tasks, leaves us mired in negative emotions, and disrupts daily activities (Kircanski et al., 2015; Kuppens et al., 2010; Kuster et al., 2012).

Even so, why do life’s unavoidable failures lead only some people to become depressed? The answer lies partly in their explanatory style—who or what they blame for their failures (or credit for their successes). Think how you might feel if you failed a test. If you can blame someone else (“What an unfair test!”), you are more likely to feel angry. If you blame yourself, you probably will feel stupid and depressed.

Depressed people tend to blame themselves. As FIGURE 13.11 illustrates, they explain bad events in terms that are stable (“I’ll never get over this”), global (“I can’t do anything right”), and internal (“It’s all my fault”). Their explanations are pessimistic, overgeneralized, self-focused, and self-blaming (Huang, 2015; Mor & Winquist, 2002; Wood et al., 1990a,b). The result may be a depressing sense of hopelessness (Abramson et al., 1989; Panzarella et al., 2006). As Martin Seligman has noted, “A recipe for severe depression is preexisting pessimism encountering failure” (1991, p. 78).

Critics point out a chicken-and-egg problem nesting in the social-cognitive explanation of depression. Which comes first? The pessimistic explanatory style or the depressed mood? The negative explanations coincide with a depressed mood, and they are indicators of depression (Barnett & Gotlib, 1988). But do they cause depression, any more than a speedometer’s reading 70 mph causes a car’s speed? Before or after being depressed, people’s thoughts are less negative. Perhaps a depressed mood triggers negative thoughts. If you temporarily put people in a bad or sad mood, their memories, judgments, and expectations do become more pessimistic. Memory researchers call this tendency to recall experiences that fit our current mood state-dependent memory.

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DEPRESSION’S VICIOUS CYCLE Depression, social withdrawal, and rejection feed one another. Depression, as we have seen, is often brought on by events that disrupt our sense of who we are and why we are worthy human beings. Such disruptions in turn lead to brooding, which is rich soil for growing negative feelings. And that negativity—being withdrawn, self-focused, and complaining—can cause others to reject us (Furr & Funder, 1998; Gotlib & Hammen, 1992). Indeed, people with depression are at high risk for divorce, job loss, and other stressful life events. Weary of the person’s fatigue, hopeless attitude, and negative comments, a spouse may threaten to leave, or a boss may question the person’s competence. New losses and stress then plunge the already depressed person into even deeper misery. Misery may love another’s company, but company does not love another’s misery.

We can now assemble pieces of the depression cycle (FIGURE 13.12): (1) Stressful experiences interpreted through (2) a brooding, negative explanatory style create (3) a hopeless, depressed state that (4) hampers the way the person thinks and acts. These thoughts and actions in turn fuel (1) further stressful experiences such as rejection. Depression is a snake that bites its own tail.

It is a cycle we can all recognize. When we feel down, we think negatively and remember bad experiences. Britain’s Prime Minister Winston Churchill called depression a “black dog” that periodically hounded him. President Abraham Lincoln was so withdrawn and brooding as a young man that his friends feared he might take his own life (Kline, 1974). As their lives remind us, people can and do struggle through depression. Most regain their capacity to love, to work, to hope, and even to succeed at the highest levels.

Each year over 800,000 despairing people worldwide will elect a permanent solution to what might have been a temporary problem (WHO, 2014b). The risk of suicide is at least five times greater for those who have been depressed than for the general population (Bostwick & Pankratz, 2000). People seldom elect suicide while in the depths of depression, when energy and will are lacking. The risk increases when they begin to rebound and become capable of following through (Chu et al., 2016).

Suicide is not necessarily an act of hostility or revenge. People—especially older adults—may choose death as an alternative to current or future suffering, a way to switch off unendurable pain and relieve a perceived burden on family members. “People desire death when two fundamental needs are frustrated to the point of extinction,” noted one psychologist: “The need to belong with or connect to others, and the need to feel effective with or to influence others” (Joiner, 2006, p. 47). Suicidal urges typically arise when people feel disconnected from others and a burden to them, or when they feel defeated and trapped by a situation they believe they cannot escape (Joiner, 2010; Taylor et al., 2011). Thus, suicide rates increase with unemployment during economic recessions (DeFina & Hannon, 2015; Reeves et al., 2014). Suicidal thoughts may also increase when people are driven to achieve a goal—to become thin or straight or rich—that proves impossible to reach (Chatard & Selimbegović, 2011).

Looking back, families and friends may recall signs that they believe should have forewarned them—verbal hints, giving possessions away, self-inflicted injuries, or withdrawal and preoccupation with death. But few who talk or think of suicide (a number that includes one-third of all adolescents and college students) actually attempt it. Of those Americans who do attempt it, only about 1 in 25 will die (AAS, 2009). Although most attempts fail, the risk of death by suicide is seven times greater among those who have attempted suicide than those who have not (Al-Sayegh et al., 2015). Each year, about 30,000 people will kill themselves—about two-thirds using guns. (Drug overdoses account for about 80 percent of suicide attempts, but only 14 percent of suicide fatalities.) States with high gun ownership are states with high suicide rates, even after controlling for poverty and urbanization (Miller et al., 2002, 2016; Tavernise, 2013). Thus, although U.S. gun owners often keep a gun to feel safer, the increased risk of suicide and homicide indicates that a gun in the home increases the odds of a family member dying (Vyse, 2016).

How can we be helpful to someone who is talking suicide—who says, for example, “I wish I could just end it all” or “I hate my life; I can’t go on”? If people write such things online, you can anonymously contact the safety teams at various social media websites (including Facebook, Twitter, Instagram, YouTube, and Tumblr). If a friend or family member talks suicide, you can (1) listen and empathize; (2) connect the person with the Suicide Prevention Lifeline (1-800-273-TALK) or campus health services; and (3) protect someone who appears at immediate risk by seeking help from a doctor, the nearest hospital emergency room, or 911. Better to share a secret than to attend a funeral.

Nonsuicidal Self-Injury

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Suicide is not the only way to send a message or deal with distress. Some people may engage in nonsuicidal self-injury (NSSI), which is more common in adolescence and among females (CDC, 2009). Such behavior, though painful, is not fatal. Those who engage in NSSI cut or burn their skin, hit themselves, pull their hair out, insert objects under their nails or skin, and tattoo themselves (Fikke et al., 2011).

Why do people hurt themselves? They tend to experience bullying and harassment (van Geel et al., 2015). They are generally less able to tolerate and regulate emotional distress (Hamza et al., 2015). They are often extremely self-critical, with poor communication and problem-solving skills (Nock, 2010). Through NSSI, they may

Does NSSI lead to suicide? Usually not. Those who engage in NSSI are typically suicide gesturers, not suicide attempters (Nock & Kessler, 2006). Suicide gesturers engage in NSSI as a desperate but non-life-threatening form of communication or when they are feeling overwhelmed. But NSSI is considered a risk factor for suicidal thoughts and future suicide attempts (Hawton et al., 2015; Willoughby et al., 2015). If people do not find help, their nonsuicidal behavior may escalate to suicidal thoughts and, finally, to suicide attempts.