Disorders of Mood
Chapter 8
Slides & Handouts by Karen Clay Rhines, Ph.D.
American Public University System
Comer, Abnormal Psychology, 8e
DSM-5 Update
Disorders of Mood

Two key emotions :

Depression


Low, sad state in which life seems dark and its
challenges overwhelming
Mania

State of breathless euphoria or frenzied energy
Comer, Abnormal Psychology, 8e
DSM-5 Update
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Disorders of Mood

People with depressive disorders suffer only from
depression



Person has no history of mania

Mood returns to normal when depression lifts
Others experience periods of mania that alternate with
periods of depression


This pattern is called unipolar depression
This pattern is called bipolar disorder
One might logically expect a third pattern – unipolar
mania, in which people suffer from mania only – but this
pattern is uncommon
Comer, Abnormal Psychology, 8e
DSM-5 Update
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Disorders of Mood

Mood problems have always captured
people’s interest

Millions of people have mood problems

Economic costs of mood problems amount to
many billions of dollars each year

The human suffering is beyond calculation
Comer, Abnormal Psychology, 8e
DSM-5 Update
4
Unipolar Depression

The term “depression” is often used to
describe general sadness or unhappiness


This loose use of the term confuses a normal
mood swing with a clinical syndrome
Depressive disorders can bring severe and
long-lasting psychological pain that may
intensify as time goes by
Comer, Abnormal Psychology, 8e
DSM-5 Update
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How Common Is
Unipolar Depression?

Around 8% of adults in the U.S. suffer from
severe unipolar depression in any given year




As many as 5% suffer from mild forms
Around 19% of all adults experience unipolar
depression at some time in their lives
The prevalence is similar in Canada, England,
France, and many other countries
The rate of depression is higher among poor
people than wealthier people
Comer, Abnormal Psychology, 8e
DSM-5 Update
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How Common Is
Unipolar Depression?


People of any age may suffer from unipolar
depression
Women are at least twice as likely as men to
experience severe unipolar depression



Lifetime prevalence: 26% of women vs. 12% of men
Among children, the prevalence is similar among boys
and girls
Approximately 85% of people with unipolar
depression recover, some without treatment

Around 40% will experience another episode later in
their lives
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Are the Symptoms of
Unipolar Depression?


Symptoms may vary from person to person
Five main areas of functioning may be
affected:

Emotional symptoms



Feeling “miserable,” “empty,” “humiliated”
Experiencing little pleasure
Motivational symptoms


Lacking drive, initiative, spontaneity
Between 6% and 15% of those with severe depression die
by suicide
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Are the Symptoms of
Unipolar Depression?

Five main areas of functioning may be
affected:

Behavioral symptoms


Cognitive symptoms




Less active, less productive
Hold negative views of themselves
Blame themselves for unfortunate events
Pessimistic
Physical symptoms

Headaches, dizzy spells, general pain
Comer, Abnormal Psychology, 8e
DSM-5 Update
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Diagnosing Unipolar Depression

A major depressive episode is a period of
two or more weeks marked by five or more
symptoms of depression

In extreme cases, symptoms are psychotic,
including

Hallucinations

Delusions
Comer, Abnormal Psychology, 8e
DSM-5 Update
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Diagnosing Unipolar Depression

DSM-5 lists several types of depressive
disorders:

Major depressive disorder


People who experience a major depressive episode
with no history of mania
Dysthymic disorder

Individuals who experience a longer-lasting (at least
two years) but less disabling pattern of depression
Comer, Abnormal Psychology, 8e
DSM-5 Update
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Diagnosing Unipolar Depression

DSM-5 lists several types of depressive
disorders:

Premenstrual dysphoric disorder


A diagnosis given to women who repeatedly
experience clinically significant depressive
symptoms during the week before menstruation
Disruptive mood regulation disorder

Characterized by a combination of persistent
depressive symptoms and recurrent outbursts of
severe temper
Comer, Abnormal Psychology, 8e
DSM-5 Update
12
What Causes
Unipolar Depression?

Stress may be a trigger for depression

People with depression experience a greater
number of stressful life events during the
month just before the onset of their symptoms

Some clinicians distinguish reactive
(exogenous) depression from endogenous
depression, which seems to be a response to
internal factors
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes
Unipolar Depression?

Today’s clinicians usually concentrate on
recognizing both the situational and the
internal aspects of any given case

The current explanations of unipolar
depression point to biological,
psychological, and sociocultural factors
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
The Biological View

Genetic factors

Family pedigree, twin, adoption, and molecular
biology gene studies suggest that some people
inherit a biological predisposition

Researchers have found that as many as 20% of
relatives of those with depression are themselves
depressed, compared with fewer than 10% of the
general population
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
The Biological View

Genetic factors

Twin studies demonstrate a strong genetic
component:

Concordance rates for identical (MZ) twins = 46%

Concordance rates for fraternal (DZ) twins = 20%

Adoption studies also have implicated a genetic
factor in cases of severe unipolar depression

Using techniques from the field of molecular
biology, researchers have found evidence that
unipolar depression may be tied to specific genes
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
The Biological View

Biochemical factors

NTs: serotonin and norepinephrine

In the 1950s, medications for high blood pressure were
found to cause depression



Some lowered serotonin, others lowered norepinephrine
The discovery of truly effective antidepressant
medications, which relieved depression by increasing
either serotonin or norepinephrine, confirmed the NT
role
Depression likely involves not just serotonin nor
norepinephrine… a complicated interaction is at work,
and other NTs may be involved
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
The Biological View

Biochemical factors

Endocrine system / hormone release

People with depression have been found to have
abnormal levels of cortisol


People with depression have been found to have
abnormal melatonin secretion


Released by the adrenal glands during times of stress
“Dracula hormone”
Other researchers are investigating deficiencies of
important proteins within neurons as tied to depression
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
The Biological View

Biochemical factors

Model has produced much enthusiasm but has
certain limitations:

Relies on analogue studies: depression-like
symptoms created in lab animals


Do these symptoms correlate with human emotions?
Measuring brain activity has been difficult and
indirect

Current studies using newer technology are attempting to
address this issue
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
The Biological View

Brain anatomy and brain circuits

Biological researchers have determined that emotional
reactions of various kinds are tied to brain circuits



These are networks of brain structures that work together,
triggering each other into action and producing a particular
kind of emotional reaction
It appears that one circuit is tied to GAD, another to panic
disorder, and yet another to OCD
Although research is far from complete, a circuit
responsible for unipolar depression has begun to
emerge

Likely brain areas in the circuit include the prefrontal cortex,
hippocampus, amygdala, and Brodmann Area 25
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
The Biological View

Immune System

This system is the body’s network of activities
and cells that fight off bacteria and other
foreign invaders

When stressed, the immune system may
become dysregulated, which some believe may
help produce depression

Support for this explanation is circumstantial but
compelling
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
The Psychological Views

Three main models:

Psychodynamic model


Behavioral model


No strong research support
Modest research support
Cognitive views

Considerable research support
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
The Psychological Views

Psychodynamic view

Link between depression and grief

When a loved one dies, an unconscious process begins and the
mourner regresses to the oral stage and experiences introjection –
a directing of feelings for the loved one onto oneself





For most people, introjection is temporary
For some, grief worsens over time; if grief is severe and long-lasting,
depression results
Those with oral stage issues (unmet or excessively met needs) are at
greater risk for developing depression
Instead of actual loss, some people experience “symbolic” (or
imagined) loss instead
Newer psychoanalysts (object relations theorists) propose that
depression results when people’s relationships leave them feeling
unsafe and insecure
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
The Psychological Views

Psychodynamic view

Strengths:

Studies have offered general support for the
psychodynamic idea that depression may be
triggered by a major loss (e.g., anaclitic depression)

Research supports the theory that early losses set
the stage for later depression

Research also suggests that people whose childhood
needs were improperly met are more likely to
become depressed after experiencing a loss
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
The Psychological Views

Psychodynamic view

Limitations:

Early losses and inadequate parenting sometimes
lead to depression but may not be typically
responsible for development of the disorder

Many research findings are inconsistent

Certain features of the model are nearly impossible
to test
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
The Psychological Views

Behavioral view

Depression results from changes in rewards and
punishments people receive in their lives


Lewinsohn suggests that the positive rewards in life
dwindle for some people, leading them to perform fewer
and fewer constructive behaviors, and they spiral toward
depression
Research supports the relationship between the
number of rewards received and the presence or
absence of depression

Social rewards are especially important
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
The Psychological Views

Behavioral view

Strengths:


Researchers have compiled significant data to support
this theory
Limitations:

Research has relied heavily on the self-reports of
depressed subjects

Behavioral studies are largely correlational and do not
establish that decreases in rewards are the initial cause
of depression
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
The Psychological Views

Cognitive views

Two main theories:

Negative thinking

Learned helplessness
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
The Psychological Views

Cognitive views

Negative thinking

Beck theorizes four interrelated cognitive
components combine to produce unipolar
depression:

Maladaptive attitudes

Self-defeating attitudes are developed during
childhood

Beck suggests that upsetting situations later in life can
trigger an extended round of negative thinking
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
The Psychological Views

Cognitive views

This negative thinking typically takes three
forms, called the cognitive triad:

Individuals repeatedly interpret (1) their
experiences, (2) themselves, and (3) their futures in
negative ways, leading to depression
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
The Psychological Views

Cognitive views

Negative thinking


Depressed people also make errors in their thinking,
including:

Arbitrary inferences

Minimization of the positive and magnification of the
negative
Depressed people also experience automatic thoughts

A steady train of unpleasant thoughts that suggest
inadequacy and hopelessness
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
The Psychological Views

Cognitive views

Strengths:


Many studies have produced evidence in support of Beck’s
explanation:

High correlation between the level of depression and the number of
maladaptive attitudes held

Both the cognitive triad and errors in logic are seen in people with
depression

Automatic thinking has been linked to depression
Limitations:

Research fails to show that such cognitive patterns are the
cause and core of unipolar depression
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
The Psychological Views

Cognitive views

Learned helplessness

This theory asserts that people become depressed
when they think that:

They no longer have control over the reinforcements
(rewards and punishments) in their lives

They themselves are responsible for this helpless state
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
The Psychological Views

Cognitive views

Learned helplessness

Theory is based on Seligman’s work with laboratory dogs

Dogs subjected to uncontrollable shock were later placed in a
shuttle box

Even when presented with an opportunity to escape, dogs
that had experienced uncontrollable shocks made no attempt
to do so

Seligman theorized that the dogs had “learned” to be
“helpless” to do anything to change negative situations, and
drew parallels to human depression
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
The Psychological Views

Cognitive views

Learned helplessness

There has been significant research support for this
model

Human subjects who undergo helplessness training score
higher on depression scales and demonstrate passivity in
laboratory trials

Animal subjects lose interest in sex and social activities

In rats, uncontrollable negative events result in lower
serotonin and norepinephrine levels in the brain
Comer, Abnormal Psychology, 8e
DSM-5 Update
35
What Causes Unipolar Depression?
The Psychological Views

Cognitive views

Learned helplessness

Recent versions of the theory focus on attributions


Internal attributions that are global and stable lead to greater
feelings of helplessness and possibly depression
 Example: “It’s all my fault” [internal]. “I ruin everything I
touch” [global] “and I always will” [stable].
If people make other kinds of attributions, this reaction is
unlikely
 Example: “She had a role in this also” [external], “the way
I’ve behaved the past couple weeks blew this
relationship” [specific]. “I don’t know what got into me –
I don’t usually act like that” [unstable].
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
The Psychological Views

Cognitive views

Learned helplessness

Some theorists have refined the helplessness model
yet again in recent years; they suggest that
attributions are likely to cause depression only
when they further produce a sense of hopelessness
in an individual
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
The Psychological Views

Cognitive views

Learned helplessness

Strengths:


Hundreds of studies have supported the relationship
between styles of attribution, helplessness, and depression
Limitations:

Laboratory helplessness does not parallel depression in every
way

Much of the research relies on animal subjects

The attributional component of the theory raises particularly
difficult questions in terms of animal models of depression
Comer, Abnormal Psychology, 8e
DSM-5 Update
38
What Causes Unipolar Depression?
Sociocultural Views

Sociocultural theorists propose that
unipolar depression is greatly influenced by
the social context that surrounds people

This belief is supported by the finding that
depression is often triggered by outside
stressors

There are two kinds of sociocultural views:

The family-social perspective

The multicultural perspective
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
Sociocultural Views

The Family-Social Perspective

The connection between declining social
rewards and depression (as discussed by the
behaviorists) is a two-way street

Depressed people often display social deficits that
make other people uncomfortable and may cause
them to avoid the depressed individuals

This leads to decreased social contact and a further
deterioration of social skills
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
Sociocultural Views

The Family-Social Perspective

Consistent with these findings, depression has been
tied repeatedly to the unavailability of social support
such as that found in a happy marriage



People who are separated or divorced display three times the
depression rate of married or widowed persons and double the
rate of people who have never been married
There also is a high correlation between level of marital
conflict and degree of sadness that is particularly strong
among those who are clinically depressed
It also appears that people who are isolated and without
intimacy are particularly likely to become depressed in times
of stress
Comer, Abnormal Psychology, 8e
DSM-5 Update
41
What Causes Unipolar Depression?
Sociocultural Views

The Multicultural Perspective

Two kinds of relationships have captured the
interest of multicultural theorists:

Gender and depression

A strong link exists between gender and depression

Women cross-culturally are twice as likely as men to
receive a diagnosis of unipolar depression

Women also appear to be younger, have more frequent
and longer-lasting bouts, and to respond less successfully
to treatment
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
Sociocultural Views

The Multicultural Perspective

A variety of theories has been offered:

The artifact theory holds that women and men are
equally prone to depression, but that clinicians
often fail to detect depression in men

The hormone explanation holds that hormone
changes trigger depression in many women

The life stress theory suggests that women in our
society experience more stress than men
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
Sociocultural Views

The Multicultural Perspective

A variety of theories has been offered:

The body dissatisfaction theory state that females in
Western society are taught, almost from birth, to
seek a low body weight and slender body shape –
goals that are unreasonable, unhealthy, and often
unattainable

The lack-of-control theory picks up the learned
helplessness research and argues that women may
be more prone to depression because they feel less
control than men over their lives
Comer, Abnormal Psychology, 8e
DSM-5 Update
44
What Causes Unipolar Depression?
Sociocultural Views

The Multicultural Perspective

A variety of theories has been offered:

The rumination theory holds that people who
ruminate when sad – keep focusing on their feelings
and repeatedly consider the causes and
consequences of their depression – are more likely
to become depressed and stay depressed longer
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
Sociocultural Views

The Multicultural Perspective

Each explanation offers food for thought and
has gathered just enough supporting evidence
to make it interesting (and just enough
contrary evidence to raise question about its
usefulness)
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
Sociocultural Views

The Multicultural Perspective

Two kinds of relationships have captured the
interest of multicultural theorists:

Cultural background and depression

Depression is a worldwide phenomenon, and certain
symptoms seem to be constant across all countries,
including sadness, joylessness, anxiety, tension, lack of
energy, loss of interest, and thoughts of suicide

Beyond such core symptoms, research suggests that the
precise picture of depression varies from country to
country
Comer, Abnormal Psychology, 8e
DSM-5 Update
47
What Causes Unipolar Depression?
Sociocultural Views

The Multicultural Perspective

Depressed people in non-Western countries
are more likely to be troubled by physical
symptoms of depression than by cognitive ones

As countries become more Westernized,
depression seems to take on the more
cognitive character it has in the West
Comer, Abnormal Psychology, 8e
DSM-5 Update
48
What Causes Unipolar Depression?
Sociocultural Views

The Multicultural Perspective

Within the United States, researchers have found
few differences in depression symptoms among
members of different ethnic or racial groups,
however, often striking differences exist between
racial/ethnic groups on the chronicity of
depression

Hispanic Americans and African Americans are 50
percent more likely than white Americans to have
recurrent episodes of depression - a finding possibly
related to limited treatment opportunities
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
Sociocultural Views

The Multicultural Perspective

In addition, although overall depression rates
are similar, differences exist in specific
populations living under oppressive
circumstances

In a study of one Native American village, lifetime
risk was 37% among women, 19% among men, and
28% overall

These findings are thought to be the result of
economic and social pressures
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Causes Unipolar Depression?
Sociocultural Views

The Multicultural Perspective

Finally, research has revealed that depression
is distributed unevenly within some minority
groups

This is not totally surprising, given that each
minority group itself is comprised of persons of
varied backgrounds and cultural values
Comer, Abnormal Psychology, 8e
DSM-5 Update
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Bipolar Disorders

People with a bipolar disorder experience
both the lows of depression and the highs
of mania

Many describe their lives as an emotional roller
coaster
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Are the Symptoms of
Mania?


Unlike those experiencing depression, people
in a state of mania typically experience
dramatic and inappropriate rises in mood
Five main areas of functioning may be
affected:

Emotional symptoms


Active, powerful emotions in search of outlet
Motivational symptoms

Need for constant excitement, involvement,
companionship
Comer, Abnormal Psychology, 8e
DSM-5 Update
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What Are the Symptoms of
Mania?

Five main areas of functioning may be affected:

Behavioral symptoms

Very active – move quickly; talk loudly or rapidly


Cognitive symptoms

Show poor judgment or planning


Flamboyance is not uncommon
May have trouble remaining coherent or in touch with reality
Physical symptoms

High energy level – often in the presence of little or no rest
Comer, Abnormal Psychology, 8e
DSM-5 Update
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Diagnosing Bipolar Disorders

People are considered to be in a full manic
episode when, for at least one week, they
display an abnormally high or irritable
mood, increased activity or energy, and at
least three other symptoms of mania


In extreme cases, symptoms are psychotic
When symptoms are less severe, the person
is said to be experiencing a hypomanic
episode
Comer, Abnormal Psychology, 8e
DSM-5 Update
55
Diagnosing Bipolar Disorders

DSM-5 distinguishes two kinds of bipolar
disorder:

Bipolar I disorder


Full manic and major depressive episodes

Most experience an alternation of episodes

Some have mixed episodes
Bipolar II disorder

Hypomanic episodes alternate with major
depressive episodes
Comer, Abnormal Psychology, 8e
DSM-5 Update
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Diagnosing Bipolar Disorders

Without treatment, the mood episodes
tend to recur for people with either type of
bipolar disorder

If people experience four or more episodes
within a one-year period, their disorder is
further classified as rapid cycling

If their episodes vary with the seasons, their
disorder is further classified as seasonal
Comer, Abnormal Psychology, 8e
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Diagnosing Bipolar Disorders

Regardless of particular pattern, individuals
with bipolar disorder tend to experience
depression more than mania over the years

In most cases, depressive episodes occur three
times as often as manic ones, and last longer
Comer, Abnormal Psychology, 8e
DSM-5 Update
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Diagnosing Bipolar Disorders

Between 1% and 2.6% of all adults in the world suffer
from a bipolar disorder at any given time, and as many
as 4% over the course of their lives


The disorders are equally common in women and men


Bipolar I seems to be a bit more common than Bipolar II
Women may experience more depressive episodes and
fewer manic episodes than men and rapid cycling is more
common in women
The disorders are more common among people with
low incomes than those with high incomes
Comer, Abnormal Psychology, 8e
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Diagnosing Bipolar Disorders

Onset usually occurs between the ages of 15
and 44 years

In most cases, the manic and depressive
episodes eventually subside, only to recur at a
later time

Generally, when episodes recur, the
intervening periods of normality grow shorter
and shorter
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Diagnosing Bipolar Disorders

A final diagnostic option:

When a person experiences numerous episodes
of hypomania and mild depressive symptoms,
a diagnosis of cyclothymic disorder is assigned

Mild symptoms for two or more years, interrupted
by periods of normal mood

Affects at least 0.4% of the population

May eventually blossom into bipolar I or II disorder
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What Causes Bipolar Disorders?

Throughout the first half of the 20th
century, the search for the cause of bipolar
disorders made little progress

More recently, biological research has
produced some promising clues

These insights have come from research into
NT activity, ion activity, brain structure, and
genetic factors
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What Causes Bipolar Disorders?

Neurotransmitters

After finding a relationship between low
norepinephrine and unipolar depression, early
researchers expected to find a link between
high norepinephrine levels and mania

This theory is supported by some research studies;
bipolar disorders may be related to overactivity of
norepinephrine
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What Causes Bipolar Disorders?

Neurotransmitters

Because serotonin activity often parallels
norepinephrine activity in unipolar depression,
theorists expected that mania would also be
related to high serotonin activity

Although no relationship with high serotonin has
been found, bipolar disorder may be linked to low
serotonin activity, which seems contradictory…
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What Causes Bipolar Disorders?

Neurotransmitters

This apparent contradiction is addressed by
the “permissive theory” about mood disorders:

Low serotonin may “open the door” to a mood
disorder and permit norepinephrine activity to
define the particular form the disorder will take:

Low serotonin + Low norepinephrine = Depression

Low serotonin + High norepinephrine = Mania
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What Causes Bipolar Disorders?

Ion activity

Ions, which are needed to send incoming messages
to nerve endings, may be improperly transported
through the cells of individuals with bipolar
disorder

Some theorists believe that irregularities in the
transport of these ions may cause neurons to fire
too easily (mania) or to stubbornly resist firing
(depression)

There is some research support for this theory
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What Causes Bipolar Disorders?

Brain structure

Brain imaging and postmortem studies have
identified a number of abnormal brain
structures in people with bipolar disorder; in
particular, the basal ganglia and cerebellum
among others

It is not clear what role such structural
abnormalities play
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What Causes Bipolar Disorders?

Genetic factors

Many theorists believe that people inherit a
biological predisposition to develop bipolar
disorders

Family pedigree studies support this theory:

Identical (MZ) twins = 40% likelihood

Fraternal (DZ) twins and siblings = 5% to 10% likelihood

General population = 1 to 2.6% likelihood
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What Causes Bipolar Disorders?

Genetic factors

Researchers have conducted genetic linkage
studies to identify possible patterns of inheritance

Other researchers are using techniques from
molecular biology to further examine genetic
patterns in large families

Such wide-ranging findings suggest that a number
of genetic abnormalities probably combine to help
bring about bipolar disorders
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