Major Depressive Disorder

Major depressive disorder involves disturbances in mood, concentration,
sleep, activity, appetite, and social behavior. It is much more than temporarily
feeling sad. It is estimated that one out of every five women and one in
fifteen men will suffer from major depression in his or her lifetime. An estimated
eighteen million Americans are affected. In 1990, $30.4 billion was
lost as a result of the illness.
A major depressive episode may develop gradually or appear quite suddenly,
without any relation to environmental factors. The symptoms of major
depressive disorder will vary among individuals, but there are some common
symptoms. People with major depressive disorder may have difficulty
falling asleep, sleep restlessly or excessively, and wake up without feeling
rested. They may experience a decrease or increase in a desire to eat. They
may crave certain foods, such as carbohydrates. They may be unable to pay
attention to things. Even minor decisions may seem impossible to make. A
loss of energy is manifested in slower mental processing, an inability to performnormal
daily routines, and slowed reaction time. Sufferers may experience
anhedonia, an inability to experience pleasure. They lose interest in
activities they used to enjoy. They ruminate about failures and feel guilty
and helpless. People with major depressive disorder tend to seek negative
feedback about themselves from others. They see no hope for improvement
and may be thinking of death and suicide. In adolescents, depression may
be manifested in anger, aggressiveness, delinquency, drug abuse, poor performance in school, or running away. Depression is a primary risk factor in
the third leading cause of death among young people, suicide.
There is probably no single cause of major depressive disorder, although
it is primarily a disorder of the brain. A chemical dysfunction and genetics
are thought to be parts of the cause. Neural circuits, which regulate mood,
thinking, sleep, appetite, and behavior, do not function normally. Neurotransmitters
are out of balance. One neurotransmitter implicated in depression
is serotonin. It is thought that in major depressive disorder there is a reduced
amount of serotonin available in the neural circuits (specifically, in
the synapses). This results in reduced or lacking nerve impulse. In many patients
with the disorder, the hormonal system that regulates the body’s response
to stress is overactive. Stress, alcohol or drug abuse, medication, or
outlook on life may trigger depressive episodes.
Cognitive theories of depression state that a negative cognitive style, such
as pessimism, represents a diathesis (a predisposition) which, in the presence
of stress, triggers negative cognitions such as hopelessness. Negative
cognitions increase the person’s vulnerability to depression. Some common
precipitants of depression in vulnerable people include marital conflict, academic
or work-related difficulty, chronic medical problems, and physical
or sexual abuse.
In most cases, medication or psychotherapy is the treatment of choice.
Treatment depends on the severity and pattern of the symptoms.With treatment,
80 percent of people with major depressive disorder return to normal
functioning.
Antidepressant drugs influence the functioning of certain neurotransmitters
(serotonin, which regulates mood, and norepinephrine, which regulates
the body’s energy). Tricyclic antidepressants act simultaneously to increase
both these neurotransmitters. This type of antidepressant often
produces intolerable side effects such as sleepiness, nervousness, dizziness,
dry mouth, or constipation. Monoamine oxidase inhibitors (MAOIs) increase
levels of these same neurotransmitters plus dopamine, which regulates
attention and pleasure. MAOIs can cause dizziness and interact negatively
with some foods. Selective serotonin reuptake inhibitors (SSRIs) have
fewer side effects but can cause nausea, insomnia or sleepiness, agitation, or
sexual dysfunction. SSRIs have also been linked to violent behavior and suicide
in children and adults, although this association is contested. Aminoketones
increase norepinephrine and dopamine, with agitation, insomnia,
and anxiety being common side effects. Selective norepinephrine reuptake
inhibitors (SNRIs) increase levels of norepinephrine and can cause dry
mouth, constipation, increased sweating, and insomnia. The selective serotonin
reuptake inhibitors and blockers (SSRIBs) increase serotonin and
elicit the fewest side effects (nausea, dizziness, sleepiness). Herbal remedies,
such as St. John’s wort, may act like SSRIs; there is some evidence that St.
John’s wort contributes to infertility. Some drugs blunt the action of a neurotransmitter
known as substance P. Other drugs reduce the level and effects of a stress-sensitive brain chemical known as corticotropin-releasing
factor (CRF). The hypothalamus, the part of the brain that manages hormone
release, increases production of CRF when a threat is detected. The
body responds with reduced appetite, decreased sex drive, and heightened
alertness. Persistent overactivation of this hormone may lead to depression.
The effects of antidepressants are due to slow-onset adaptive changes in
neurons. They may take several weeks to have a noticeable effect.
Psychotherapy works by changing the way the brain functions. Cognitivebehavioral
therapy helps patients change the negative styles of thinking and
behaving associated with depression. Therapies teach patients new skills to
cope better with life, increase self-esteem, cope with stress, and better deal
with interpersonal relationships. There is evidence that severe depression
responds most favorably with a combination of medication and psychotherapy.
Electroconvulsive therapy (ECT) is an effective treatment for major depressive
disorder. The treatment was first developed in 1934. Between 80
percent and 90 percent of people with the disorder show great improvement
with ECT, which produces a seizure in the brain by applying electrical
stimulation to the brain through electrodes placed on the scalp. ECT reduces
the level of CRF. The treatment is usually repeated to obtain a therapeutic
response. Common, yet short-lived, side effects include memory loss
and other cognitive deficits. 542