Causes of Mood Disorders

477
in review
Mood Disorders
MOOD DISORDERS
Type
Typical Symptoms
Related Features
Major depressive
disorder
Deep sadness, feelings of
worthlessness, changes in
eating and sleeping habits,
loss of interest and pleasure
Lasts weeks or months; may
occur in repeating episodes;
severe cases may include
delusions
Dysthymic disorder
Similar to major depressive
disorder, but less severe and
longer lasting
Hospitalization usually
not necessary
Bipolar disorder
Alternating extremes of
mood, from deep depression
to mania, and back
Manic episodes include
impulsivity, unrealistic
optimism, high energy,
severe agitation
Cyclothymic
disorder
Similar to bipolar disorder,
but less severe
Hospitalization usually not
necessary
?
1. The risk of suicide is associated with
more than with any other
symptom of disorder.
2. Cyclothymic disorder is the bipolar version of
.
3. Women are
likely than men to try suicide, but men are
to succeed.
likely
anyone who tries to reason with them or “slow them down,” and they may make impulsive and unwise decisions, including spending their life savings on foolish schemes.
In bipolar disorder, episodes of mania may alternate with periods of deep depression. Sometimes, periods of relatively normal mood separate these extremes (Tohen
et al., 2003). This pattern has also been called manic depression. Compared with major
depressive disorder, bipolar disorder is rare. It occurs in only about 1 percent of adults,
and it affects men and women about equally. Even less common is bipolar II disorder,
in which major depressive episodes alternate with episodes known as hypomania, which
are less severe than the manic phases seen in bipolar I disorder.
Slightly more common is a pattern of milder mood swings known as cyclothymic
disorder, the bipolar equivalent of dysthymic disorder. Like major depressive disorder,
bipolar disorders are extremely disruptive to a person’s ability to work or maintain social
relationships (Goldberg, Harrow, & Grossman, 1995), and they are often accompanied
by anxiety disorders (Freeman, Freeman, & McElroy, 2002). “In Review: Mood Disorders” summarizes the main types of mood disorders.
LINKAGES
Are some psychological
disorders inherited? (a link
to Biology and Behavior)
Causes of Mood Disorders
Research on the causes of mood disorders has focused on biological, psychological, and
sociocultural risk factors. The more of these risk factors people have, the more likely
they are to experience a mood disorder.
Biological Factors The role of genetics is suggested by twin studies and family stud-
cyclothymic disorder A mood disorder
characterized by an alternating pattern
of mood swings that are less extreme
than those of bipolar disorder.
ies showing that mood disorders tend to run in families (Cho et al., 2005; Kendler et al.,
2006; Kieseppä et al., 2004; Weissman et al., 2005). For example, bipolar disorder is much
more likely to be seen in both members of genetically identical twin pairs than in genetically nonidentical twins (Bowman & Nurnberger, 1993; Egeland et al., 1987; McGuffin
et al., 2003). Family studies also show that those who are closely related to people
with bipolar disorder are more likely than others to develop the disorder themselves
478
Chapter 12 Psychological Disorders
TREATING SAD Seasonal affective disorder (SAD) can often be relieved by exposure to full-spectrum light for as little
as a couple of hours a day (Terman &
Terman, 2005).
(Blackwood, Visscher, & Muir, 2001). Major depressive disorder, too, is more likely to
occur in both members of identical, compared with nonidentical, twins (Klein et al., 2001;
Levinson, 2006). This genetic influence is especially strong in female twins (Bierut et al.,
1999). Researchers continue to look for the specific genes that might be involved in the
transmission of elevated risk for mood disorders (Cheng et al., 2006; Greenwood et al.,
2006; Hariri et al., 2005; Konradi et al., 2004; MacQueen, Hajek, & Alda, 2005).
Other biological factors that may contribute to mood disorders include malfunctions in regions of the brain involved in mood, imbalances in the brain’s neurotransmitter systems, malfunctioning of the endocrine system, disruption of biological
rhythms, and underdevelopment in the frontal lobes, hippocampus, or other brain areas
(Blumberg et al., 2003; Geuze, Vermetten, & Bremner, 2005; Jacobs, 2004; MacQueen
et al., 2005; Milak et al., 2005; Staley et al., 2006; Strakowski, DelBello, & Adler, 2005).
All of these conditions may themselves be influenced by genetics.
As for the role of neurotransmitters, norepinephrine, serotonin, and dopamine were
implicated decades ago when scientists discovered that drugs capable of altering these
substances also relieved mood disorders. However, the precise nature of the relationship
between neurotransmitters and mood disorders is still not fully understood (Martinot
et al., 2001; Schloss & Williams, 1998; U.S. Surgeon General, 1999).
Mood disorders have also been related to malfunctions of the endocrine system,
especially the subsystem involved in the body’s responses to stress (see the chapter on
health, stress, and coping). For example, research shows that as many as 70 percent of
depressed people secrete abnormally high levels of the stress hormone cortisol (Dinan,
2001; Posener et al., 2000).
The cycles of mood swings seen in bipolar disorders and in recurring episodes of
major depressive disorder suggest that mood disorders may be related to stressful triggering events (Miklowitz & Alloy, 1999). They may also be related to disturbances in the
body’s biological clock, which is described in the chapter on biology and behavior
(Goodwin & Jamison, 1990). This second possibility seems especially likely to apply to
the 15 percent of depressed people who consistently experience a calendar-linked pattern of depressive episodes known as seasonal affective disorder (SAD). During months
of shorter daylight, these people slip into severe depression, accompanied by irritability
and excessive sleeping. Their depression tends to lift as daylight hours increase (Faedda
et al., 1993). Disruption of biological rhythms is also suggested by the fact that many
depressed people tend to have trouble sleeping—partly because during the day, their biological clocks may be telling them it is the middle of the night. Resetting the biological
clock through methods such as sleep deprivation or light stimulation has relieved depression in many cases (Golden et al., 2005; Lewy et al., 2006; Terman et al., 2001).
479
Mood Disorders
Researchers have come to recognize that the
biological factors involved in mood disorders always operate in combination with psychological and social factors (Jacobs, 2004). As mentioned earlier, the very nature of
depressive symptoms can depend on the culture in which a person lives. Biopsychosocial explanations of mood disorders also emphasize the impact of anxiety, negative
thinking, and the other psychological and emotional responses triggered by trauma,
losses, and other stressful events (Kendler, Hettema, et al., 2003; Kendler, Kuhn, &
Prescott, 2004; Monroe et al., 1999). For example, the higher rate of depression among
females—and especially among poor, ethnic-minority single mothers—has been attributed to their greater exposure to stressors of all kinds (Brown & Moran, 1997; Miranda
& Green, 1999). Environmental stressors affect men, too (Bierut et al., 1999), which
may be one reason that gender differences are smaller in countries in which men and
women face equally stressful lives. Still, differing stressors may not be the only source
of these gender differences (Kendler, Thornton, & Prescott, 2001).
A number of social-cognitive theories suggest that the way people think about their
stressors can increase or decrease the likelihood of mood disorders. One of these theories is based on the learned helplessness research described in the chapter on learning.
Just as animals become inactive and appear depressed when they have no control over
negative events (El Yacoubi et al., 2003), humans may experience depression as a result
of feeling incapable of controlling their lives, especially the stressors confronting them
(Klein & Seligman, 1976; Seligman, 1991). But most of us have limited control, so why
aren’t we all depressed? The ways in which people learn to think about events in their
lives may hold the key. For example, Aaron Beck’s (1967, 1976) cognitive theory of
depression suggests that depressed people develop mental habits of (1) blaming themselves when things go wrong, (2) focusing on and exaggerating the negative side of
events, and (3) jumping to overly generalized, pessimistic conclusions. Such cognitive
habits, says Beck, are errors that lead to depressing thoughts and other symptoms of
depression (Beck & Beck, 1995). Depressed people, in fact, do tend to think about significant negative events in ways that are likely to increase or prolong their depression
(Gotlib & Hammen, 1992; Gotlib et al., 2004; Strunk, Lopez, & DeRubeis, 2006).
Severe, long-lasting depression is especially likely among people who blame their lack
of control or other problems on a permanent, generalized lack of personal competence
rather than on a temporary mistake or some external cause (Seligman et al., 1988). This
negative attributional style may be another important cognitive factor in depression
(Alloy, Abramson, & Francis, 1999; Hankin, Fraley, & Abela, 2005; Hunt & Forand, 2005).
Are depressed people’s unusually negative beliefs about themselves actually helping to
cause their depression, or are they merely symptoms of it? A number of studies have
assessed the attributional styles of large samples of nondepressed people and then kept
in touch with them to see whether individuals with negative self-beliefs are more likely
to become depressed when stressors occur. These longitudinal studies suggest that a negative attributional style is, in fact, a risk factor for depression, not just a result of being
depressed (Garber, Keiley, & Martin, 2002; Gibb et al., 2004; Runyon & Kenny, 2002;
Satterfield, Folkman, & Acree, 2002). In one study, for example, adolescents who held
strong negative self-beliefs were more likely than other youngsters to develop depression
when faced with stress later in life (Lewinsohn, Joiner, & Rohde, 2001).
Social-cognitive theorists also suggest that whether depression continues or worsens
depends in part on how people respond once they start to feel depressed. Those who
continuously think about negative events, about why they occur, and even about being
depressed are likely to feel more and more depressed (Just & Alloy, 1997; Sarin, Abela,
& Auerbach, 2005). According to Susan Nolen-Hoeksema (1990, 2001), this ruminative
style is especially characteristic of women and may help explain gender differences in
the frequency of depression. When men start to feel sad, she says, they tend to use a
distracting style. In other words, they engage in activity that distracts them from their
concerns and helps bring them out of their depressed mood (Hankin & Abramson,
2001; Just & Alloy, 1997; Nolen-Hoeksema, Morrow, & Fredrickson, 1993).
Notice that social-cognitive explanations of depression are consistent with the
diathesis-stress explanation of disorder (Hankin & Abramson, 2001). These explanations suggest that certain cognitive styles serve as a predisposition (or diathesis) that
Psychological and Social Factors