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Affective Disorders (Treatments (For Major Depressive Disorder (MDD)…
Affective Disorders
Treatments
For Mania
Lithium:
- Chemical element
- Lithium salts are used to treat bipolar disorder
- Most effective in treating manic phase of bipolar affective disorder
- Once mania is eliminated, depression usually does not follow
- Therapeutic effect of lithium is very rapid. The mechanism of action is unknown.
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Treatment Response:
- Even when depressed patients respond to treatment with antidepressant drugs, they do not do so immediately
- Improvement in symptoms is not usually seen before two to three weeks of drug treatment
- In contrast, the effects of other treatments (lithium, ECT, DBS, VNS, sleep deprivation) are more rapid
- For example, seizures induced by ECT can often reduce the symptoms of a deep depression within a few days
Types of Disorders
Major Depressive Disorder (MDD): serious mood disorder that consists of unremitting depression or periods of depression that do not alternate with periods of mania
- Depression has a prevalence of approximatively 7% in women and 3% in men.
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Causes
Hereditary
- Evidence indicates that a tendency to develop an affective disorder is a heritable characteristic
- It has been found that if one member of a set of monozygotic twins was afflicted with an affective disorder, the likelihood that the other twin was similarly afflicted was 69%. In contrast, the concordance rate for dizygotic twins was only 13%.
- Genetic studies have found evidence that genes on several chromosomes may be implicated in development of affective disorders
Monoamine:
- Based largely on the success tricyclic and SSRI treatments, the monoamine hypothesis of depression was developed. The idea is that depression is caused by insufficient activity of monoaminergic neurons.
- Because symptoms of depression are not relieved by potent dopamine agonists such as amphetamine or cocaine, most investigators have focused their research efforts on the other two monoamines: norepinephrine and serotonin.
Neural Pathway
Role of Frontal Cortex
Functional Imaging Scans
- Functional imaging scans have been done on many depressed patients, both before and after a variety of successful treatments.
- There are few (if any) correlations. However, the argument has been made that one area of the anterior cingulate cortex (known as area 25) becomes less active after successful treatments.
Role of Neurogenesis
Neurogenesis:
- Neurogenesis can take place in dentate gyrus—region of hippocampal formation—in adult brain
- Several studies with laboratory animals have shown that stressful experiences that produce the symptoms of depression suppress hippocampal neurogenesis
- Administration of antidepressant treatments, including MAO inhibitors, tricyclic antidepressants, SSRIs, ECT, and lithium, increases neurogenesis
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