Mood disorders are characterized by marked disturbances in
emotional state, which affect thinking, physical symptoms, social relationships, and
behavior. If mood is viewed as a continuum, mood disorders occur when a person
experiences moods that lie at either extreme of the continuum. Mood disorders are of
two basic types: unipolar or bipolar. People with unipolar disorders experience
moods that are at the depressive end of the continuum. People with bipolar disorders
experience moods that are at both ends of the continuum.
Mood disorders are generally episodic, which means they tend to come and go.
The duration of the disturbed emotional state and the pattern of its occurrence
determine how a mood disorder is diagnosed.
A person with dysthymic disorder experiences a depressed mood
for a majority of days over at least two years.
Major Depressive Disorder
Major depressive disorder is characterized by at least one
major depressive episode. A major depressive episode is a period of
at least two weeks in which a person experiences some or all of the following
- Constant sadness or irritability
- Loss of interest in almost all activities
- Changed sleeping or eating patterns
- Low energy
- Feelings of worthlessness or guilt
- Difficulty concentrating
- Recurrent thoughts about suicide
Major depressive disorder is much more common in women than in men.
Bipolar disorders involve at least one distinct period when a
person exhibits manic symptoms. Manic symptoms include any or all of the
- Feelings of being high
- Decreased need for sleep
- Inflated self-esteem or grandiosity
- Fast and pressured speech
- Increased interest in pleasurable activities that have the potential
for harmful consequences.
People with bipolar disorders usually also experience major depressive
episodes. Men and women are equally likely to suffer from bipolar
Etiology of Mood Disorders
Researchers believe that many different influences interact to produce
Biological influences include the following:
Genetic predisposition: Twin studies suggest
that people can be genetically predisposed to major depressive
disorder and bipolar disorders. Concordance rates for both major
depressive disorder and bipolar disorders are higher for identical
twins than fraternal twins. Genetic factors seem to be
implicated more in depression among women than among men.
Neurotransmitters: Research shows that the
neurotransmitters norepinephrine and serotonin are involved in mood
Brain structure: Some research indicates that people
with chronic depression tend to have a smaller hippocampus and amygdala
in the brain, perhaps because of an excess of the stress hormone
Many researchers have studied the various cognitive factors involved
Learned helplessness: The psychologist
Martin Seligman proposed that depression results
from learned helplessness, or a tendency to give up
passively in the face of unavoidable stressors. Seligman pointed out
that people who have a pessimistic explanatory style are likely to
Self-blame: Depressed people tend to attribute
negative events to internal, stable, and global factors. When a problem
occurs, they blame themselves rather than situational factors. They
believe the problem is likely to be permanent, and they overgeneralize
from the problem to their whole lives.
Low self-esteem: Some researchers have suggested that
a pessimistic worldview is only one of several factors that contribute
to depression. They say that other factors such as low self-esteem and
stress also play an important role. All these lead to hopelessness,
which then leads to depression.
Rumination: Rumination, or brooding about problems,
is associated with longer periods of depression. Some researchers
believe that women have higher rates of depression because they tend to
ruminate more than men.
Although many researchers believe negative thinking makes people
susceptible to depression, most also acknowledge a two-way relationship
between depression and negative thinking. Negative thinking makes people
susceptible to depression, and depression makes people more likely to think
Various interpersonal influences are also linked to depression:
Lack of social network: Depressed people
tend to have less social support than other people, and the
relationship between social support and depression is likely to be
two-way. People with poor social skills may be more likely to
develop depression. Once people are depressed, they tend to be
unpleasant companions, which further reduces their social
Loss of an important relationship: Some researchers
have suggested that depression can result when people lose important
The onset and course of mood disorders may be influenced by stress.
Stress also affects people’s responses to treatment and whether they are
likely to have a relapse. Some researchers have suggested that women are
more vulnerable to depression because they tend to experience more stress in
the form of discrimination, poverty, and sexual abuse and because they may
have less satisfying work and family lives than men.
Even if people are usually happy and have friends and family to rely
on, they can still become depressed. Major catastrophes and personal traumas
can also contribute to depression. For instance, living in a war zone,
having a home destroyed by fire, suffering from a chronically painful or
debilitating illness, going through a divorce, or losing a loved one can all
bring on depression.