Understanding Depressive Disorders and Bipolar Disorder
Life after depression J. K. Rowling, author of the Harry Potter books, reported suffering acute depression—a “dark time,” with suicidal thoughts—between ages 25 and 28. It was a “terrible place,” she said, but it formed a foundation that allowed her “to come back stronger” (McLaughlin, 2010).
Today’s psychologists continue to sleuth why people have depressive disorders and bipolar disorder, and to design more effective ways to treat and prevent them. Here, we focus primarily on depressive disorders. One research group summarized the facts that any theory of depression must explain, including the following (Lewinsohn et al., 1985, 1998, 2003):
- Behavioral and cognitive changes accompany depression. People trapped in a depressed mood become inactive and feel alone, empty, and without a bright or meaningful future (Bullock & Murray, 2014; Khazanoy & Ruscio, 2016; Smith & Rhodes, 2014). They avoid positive information and attend selectively to negative events (Peckham et al., 2010; Winer & Salem, 2016). They more often recall negative information. They expect negative outcomes (my team will lose, my grades will fall, my love will fail). When the depression lifts, these behavioral and cognitive accompaniments disappear. Nearly half the time, people also exhibit symptoms of another disorder, such as anxiety or substance abuse.
- Depression is widespread. Worldwide, 350 million people have major depressive disorder and 60 million people have bipolar disorder (WHO, 2017a). At some point during their lifetime, depression has plagued 11 percent of Canadian 15- to 24-year-olds (Findlay, 2017). Depression’s commonality suggests that its causes, too, must be common.
- Women’s risk of major depressive disorder is nearly double men’s. In 2009, when Gallup pollsters asked more than a quarter-million Americans if they had ever been diagnosed with depression, 13 percent of men and 22 percent of women said they had (Pelham, 2009). When Gallup asked Americans if they had experienced sadness “during a lot of the day yesterday,” 17 percent of men and 28 percent of women answered Yes (Mendes & McGeeney, 2012). The depression gender gap—with U.S. women experiencing depression 1.7 times more often than men (CDC, 2014a)—has been found worldwide (Figure 67.1). The trend begins in adolescence; preadolescent girls are not more depression-prone than are boys (Kuehner, 2017). After reaching puberty, girls also become more vulnerable than boys to eating disorders, self-injury, and anxiety (Mendle et al., 2016). Menopause—more specifically, “the 5 or 6 years surrounding the last menstrual period”—is also a time of women’s increased depression risk, though in later life, the depression gender gap diminishes (Gordon et al., 2016; Patten et al., 2016).
The factors that put women at risk for depression (genetic predispositions, child abuse, low self-esteem, marital problems, and so forth) similarly put men at risk (Kendler et al., 2006). Yet women are more vulnerable to disorders involving internalized states such as depression, anxiety, and inhibited sexual desire. Women experience more situations that increase their risk for depression, such as receiving less pay for equal work, juggling multiple roles, and caring for children and elderly family members (Freeman & Freeman, 2013). Men’s disorders tend to be more external—alcohol use disorder, and disorders related to antisocial conduct and lack of impulse control. When women get sad, they often get sadder than men do. When men get mad, they often get madder than women do.
- Most major depressive episodes self-terminate. Therapy often helps and tends to speed recovery. But even without professional help, most people recover from depression and return to normal. The plague of depression comes and, a few weeks or months later, it goes, though for some (about half), it eventually returns (Curry et al., 2011; Klein & Kotov, 2016). Only about 20 percent experience chronic depression (Klein, 2010). On average, a person with major depressive disorder today will spend about three-fourths of the next decade in a normal, nondepressed state (Furukawa et al., 2009). In one study of over 20,000 Canadians, an enduring recovery was more likely if the first episode struck later in life, there was no prior history of depression, people experienced minimal physical or psychological stress, and they had ample social support (Fuller-Thomson et al., 2016).
- Stressful events related to work, marriage, and close relationships often precede depression. As anxiety is a response to the threat of future loss, depression is often a response to past and current stress. Experiencing childhood abuse doubles a person’s risk of adult depression (Nelson et al., 2017). About 1 person in 4 diagnosed with depression has been brought down by a significant loss or trauma, such as a loved one’s death, a ruptured marriage, a physical assault, or a lost job (Kendler et al., 2008; Monroe & Reid, 2009; Orth et al., 2009; Wakefield et al., 2007). Moving to a new culture also increases risk for depression, especially among younger people who have not yet formed their identities (Zhang et al., 2013). One long-term study (Kendler, 1998) tracked rates of depression in 2000 people. The risk of depression ranged from less than 1 percent among those who had experienced no stressful life event in the preceding month to 24 percent among those who had experienced three such events in that month. For some, grappling with life’s minor daily stressors can also negatively impact mental health. People who overreacted to minor stressors, such as a broken appliance, were more often depressed 10 years later (Charles et al., 2013).
- Compared to generations past, depression strikes earlier (now often in the late teens) and affects more people, with the highest rates among young adults in developed countries. Although adolescent depression rates have recently leveled off, this trend has been reported in Canada, the United States, England, France, Germany, Italy, Lebanon, New Zealand, Puerto Rico, and Taiwan (Cross-National Collaborative Group, 1992; Kessler et al., 2010; Olfson et al., 2015). In one study, 12 percent of Australian adolescents reported symptoms of depression (Sawyer et al., 2000). Most hid it from their parents, almost 90 percent of whom perceived their depressed teen as not suffering depression. In North America, young adults are three times more likely than their grandparents to report having recently—or ever—suffered depression (despite the grandparents’ many more years of being at risk). The increase may reflect a cultural difference of today’s young adults’ greater willingness to disclose depression.
Figure 67.1 Gender and major depressive disorder
Interviews with 89,037 adults in 18 countries (10 of which are shown here) confirm what many smaller studies have found: Women’s risk of major depressive disorder is nearly double men’s.
Armed with these facts, today’s researchers propose biological and cognitive explanations of depression, often combined in a biopsychosocial perspective.
The Biological Perspective
Depression is a whole-body disorder. It involves genetic predispositions and biochemical imbalances, as well as negative thoughts and a gloomy mood.
Genetic Influences
Depressive disorders and bipolar disorder run in families. As one researcher noted, emotions are “postcards from our genes” (Plotkin, 1994). The risk of being diagnosed with one of these disorders increases if your parent or sibling has the disorder (Sullivan et al., 2000; Weissman et al., 2016). 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 twins raised apart (DiLalla et al., 1996). Summarizing the major twin studies, one research team estimated the heritability of major depressive disorder—the extent to which individual differences are attributable to genes—at 40 percent (Polderman et al., 2015; see also Figure 67.2 for another study’s similar heritability findings for this and other disorders).
Figure 67.2 The heritability of various psychological disorders
Using aggregated data from studies of identical and fraternal twins, researchers estimated the heritability of bipolar disorder, schizophrenia, anorexia nervosa, major depressive disorder, and generalized anxiety disorder (Bienvenu et al., 2011). (Heritability was calculated by a formula that compares the extent of similarity among identical versus fraternal twins.)
To tease out the genes that put people at risk for depression, some researchers have turned to linkage analysis. First, geneticists find families in which the disorder appears across several generations. Next, the researchers examine DNA from affected and unaffected family members, looking for differences. Linkage analysis points them to a chromosome neighborhood; “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. Researchers continue to identify culprit gene variations that may open the door to more effective drug therapy (Hyde et al., 2016; Power et al., 2017).
The Depressed Brain
Scanning devices let us eavesdrop on the brain’s activity during depressed and manic states. One study gave 13 elite Canadian swimmers the wrenching experience of watching a video of the swim in which they failed to make the Olympic team or failed at the Olympic games (Davis et al., 2008). Functional MRI scans showed the disappointed swimmers experiencing brain activity patterns similar to those of people with depressed moods.
Many studies have found diminished brain activity during slowed-down depressive states, and more activity during periods of mania (Figure 67.3). Depression can cause the brain’s reward centers to become less active (Miller et al., 2015; Stringaris et al., 2015). During positive emotions, the left frontal lobe and an adjacent reward center become more active (Davidson et al., 2002; Robinson et al., 2012).
Figure 67.3 The ups and downs of bipolar disorder
These top-facing PET scans show that brain energy consumption rises and falls with the patient’s emotional switches. Red areas are where the brain rapidly consumes glucose.
Neuroscientists have also discovered altered brain structures in people with bipolar disorder. These studies discovered a decrease in myelinated axons (see Module 9) and enlarged fluid-filled ventricles (Arnone et al., 2009; Hibar et al., 2016).
Neurotransmitter systems also influence depressive disorders and bipolar disorder. Norepinephrine, which increases arousal and boosts mood, is scarce during depression and overabundant during mania. Drugs that decrease mania reduce norepinephrine.
Serotonin is also scarce or inactive during depression (Carver et al., 2008). One well-publicized study of New Zealand young adults found that the recipe for depression combined two necessary ingredients—significant life stress plus a variation of a serotonin-controlling gene (Caspi et al., 2003; Moffitt et al., 2006). Depression arose from the combination of an adverse environment plus a genetic susceptibility, but not from either alone. But stay tuned: The story of gene-environment interactions is still being written, as other researchers debate the reliability of this result (Culverhouse et al., 2013; Karg et al., 2011).
Drugs that relieve depression tend to increase norepinephrine or serotonin supplies by blocking either their reuptake (as Prozac, Zoloft, and Paxil do with serotonin) or their chemical breakdown. Repetitive physical exercise, such as jogging, reduces depression in part because it increases serotonin, which affects mood and arousal (Airan et al., 2007; Ilardi, 2009; Jacobs, 1994). In one study, running for two hours increased brain activation in regions associated with euphoria (Boecker et al., 2008). To run away from a bad mood, you can use your own two feet.
Nutritional Effects
What’s good for the heart is also good for the brain and mind. People who eat a heart-healthy “Mediterranean diet” (heavy on vegetables, fish, and olive oil) have a comparatively low risk of developing heart disease, stroke, late-life cognitive decline, and depression—all of which are associated with inflammation (Kaplan et al., 2015; Psaltopoulou et al., 2013; Rechenberg, 2016). Excessive alcohol use also correlates with depression, partly because depression can increase alcohol use but mostly because alcohol misuse leads to depression (Fergusson et al., 2009).
The Social-Cognitive Perspective
Biological influences contribute to depression, but in the nature–nurture dance, our life experiences also play a part. Diet, drugs, stress, and other environmental influences lay down epigenetic marks, molecular genetic tags that can turn certain genes 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 view life through the dark glasses of low self-esteem (Orth et al., 2016). Their intensely negative assumptions about themselves, their situation, and their future lead them to magnify bad experiences and minimize good ones (Wenze et al., 2012). Listen to Norman, a Canadian university professor, recalling his depression:
I [despaired] of ever being human again. I honestly felt subhuman, lower than the lowest vermin. Furthermore, I was self-deprecatory and 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. (Endler, 1982, pp. 45–49)
Expecting the worst, depressed people’s self-defeating beliefs and their negative explanatory style feed their depression.
Negative Thoughts, Negative Moods, and Gender
Women may respond more strongly to stress (Hankin & Abramson, 2001; Mazure et al., 2002; Nolen-Hoeksema, 2001, 2003). For example, 38 percent of women and 17 percent of men entering American colleges and universities have reported feeling at least occasionally “overwhelmed by all I have to do” (Pryor et al., 2006). Relationship stresses also affect teen girls more than boys (Hamilton et al., 2015).
This gender stress difference may help explain why, beginning in their early teens, women have been nearly twice as vulnerable to depression. Susan Nolen-Hoeksema (2003) related women’s higher risk of depression to what she described as their tendency to ruminate or overthink. Staying focused on a problem (thanks to the continuous firing of a frontal lobe area that sustains attention)—can be adaptive (Altamirano et al., 2010; Andrews & Thomson, 2009a,b). But relentless, self-focused rumination can distract us, increase negative emotion, and disrupt daily activities (Johnson et al., 2016; Kircanski et al., 2015; Yang et al., 2017). Comparisons can also feed misery. While Josh is happily playing video games, lonely Lauren scrolls through her social media feed and sees Maria having a blast with friends, Angelique enjoying a family vacation, and Tyra looking super in a swimsuit. In response, Lauren broods: “My life is terrible.”
Rumination runs wild It’s normal to think about our flaws. But dwelling constantly on negative thoughts—particularly negative thoughts about ourselves—makes it difficult to believe in ourselves and solve problems. People sometimes seek therapy to reduce their rumination.
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. Think of how you might feel if you failed a test. If you can externalize the blame (“What an unfair test!”), you are more likely to feel angry. If you blame yourself, you probably will feel stupid and depressed.
“ I think I, like a lot of people, have that type of brain where I find it interesting or fulfilling to worry about something.”
Comedian Maria Bamford
So it is with depressed people, who often explain bad events in terms that are stable (“It’s going to last forever”), global (“It’s going to affect everything I do”), and internal (“It’s all my fault”) (Figure 67.4). Depression-prone people respond to bad events in an especially self-focused, self-blaming way (Huang, 2015; Mor & Winquist, 2002; Wood et al., 1990a,b). When they describe themselves, their brains show extra activity in a region that processes self-relevant information (Sarsam et al., 2013). Their self-esteem is also more plastic—it climbs with praise and plummets with threats (Butler et al., 1994).
Figure 67.4 Explanatory style and depression
After a difficult experience, a depression-prone person may respond with a negative explanatory style.
Self-defeating beliefs may arise from learned helplessness, the hopelessness and passive resignation humans and other animals learn when they experience uncontrollable painful events (Maier & Seligman, 2016) (see Module 29). Pessimistic, overgeneralized, self-blaming attributions may create 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). What then might we expect of new college students who exhibit a pessimistic explanatory style? Lauren Alloy and her colleagues (1999) monitored several hundred students every 6 weeks for 2.5 years. Among those identified as having a pessimistic thinking style, 17 percent had a first episode of major depression, as did only 1 percent of those who began college with an optimistic thinking style.
Why is depression so common among young Westerners? Seligman (1991, 1995) pointed to the rise of individualism and the decline of commitment to religion and family. In non-Western cultures, where close-knit relationships and cooperation are the norm, major depressive disorder is less common and less tied to self-blame over personal failure (Ferrari et al., 2013; WHO, 2004a). In Japan, for example, depressed people instead tend to report feeling shame over letting others down (Draguns, 1990a).
Critics note 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. (Before or after being depressed, people’s thoughts are less negative. Perhaps a depressed mood triggers negative thoughts.) But do negative thoughts cause depression, any more than a speedometer’s reading causes a car’s speed? If you temporarily put people in a bad or sad mood, their memories, judgments, and expectations suddenly become more pessimistic. Memory researchers call this tendency to recall experiences that fit our current good or bad mood state-dependent memory (Module 32).
“You should never engage in unsupervised introspection.”
Depression’s Vicious Cycle
Depression is both a cause and an effect of stressful experiences that disrupt our sense of who we are and why we are worthy human beings. Such disruptions can lead to brooding, which amplifies negative feelings. Being withdrawn, self-focused, and complaining can in turn elicit rejection (Furr & Funder, 1998; Gotlib & Hammen, 1992). Indeed, people in the throes of depression are at high risk for divorce, job loss, and other stressful life events. Weary of the person’s fatigue, hopeless attitude, and negativity, a spouse may threaten to leave or a boss may begin to question the person’s competence. (This provides another example of genetic-environmental interaction: People genetically predisposed to depression more often experience depressing events.) Rejection and depression feed each other. Misery may love another’s company, but company does not love another’s misery.
“ Man never reasons so much and becomes so introspective as when he suffers, since he is anxious to get at the cause of his sufferings.”
Luigi Pirandello, Six Characters in Search of an Author, 1922
We can now assemble some of the pieces of the depression puzzle (Figure 67.5): (1) Stressful experiences interpreted through (2) a ruminating, pessimistic explanatory style create (3) a hopeless, depressed state that (4) hampers the way the person thinks and acts. This, in turn, fuels (1) further stressful experiences such as rejection. Depression is a snake that bites its own tail.
Figure 67.5 The vicious cycle of depressed thinking
Therapists recognize this cycle, and they work to help depressed people break out of it by changing their negative thinking, turning their attention outward, and engaging them in more pleasant and competent behavior.
None of us are immune to the dejection, diminished self-esteem, and negative thinking brought on by rejection or defeat. Even small losses can temporarily sour our thinking. In one study, researchers studied some avid Indiana University basketball fans who seemed to regard the team as an extension of themselves (Hirt et al., 1992). After the fans watched their team lose or win, the researchers asked them to predict the team’s future performance and their own. After a loss, the morose fans offered bleaker assessments not only of the team’s future but also of their own likely performance at throwing darts, solving anagrams, and getting a date. When things aren’t going our way, it may seem as though they never will.
“ Some cause happiness wherever they go; others, whenever they go.”
Irish writer Oscar Wilde (1854–1900)
It is a cycle we can all recognize. Bad moods feed on themselves: 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. Abraham Lincoln was so withdrawn and brooding as a young man that his friends feared he might take his own life (Kline, 1974). Poet Emily Dickinson was so afraid of bursting into tears in public that she spent much of her adult life in seclusion (Patterson, 1951). As their lives remind us, people can and do struggle through depression. Most regain their capacity to love, to work, and even to succeed at the highest levels.