What do antidepressants do?
Answered by Craig C. Freudenrich and Discovery Fit & Health
  • Craig C. Freudenrich

    Craig C. Freudenrich

  • Discovery Fit & Health

    Discovery Fit & Health

  1. About 1 in 10 American adults have depression [CDC]. Depression is a mood disorder that can affect people of any age, but most likely those between 45 and 64 years old. The causes of depression are not known exactly, but current thinking is that depression is associated with a chemical imbalance in the area of the brain responsible for mood and emotions -- the limbic system and upper brainstem. The chemicals are neurotransmitters, such as serotonin, dopamine and norepinephrine, which are involved in communication between nerve cells in these areas of the brain.  Many antidepressant drugs increase the concentrations of these chemicals by blocking various aspects of synaptic transmission:

    • Selective serotonin reuptake inhibitors (SSRIs) -- block serotonin reuptake in the brain. This helps to keep serotonin levels balanced so that the brain's messages in mood centers work as intended. SSRIs include sertraline, paroxetine, fluoxetine, and escitalopram. One problem with SSRIs is that patients may lose their sexual desire while taking them. A new SSRI called vilazodone was approved in 2011 that reportedly treats depression without affecting sexual desire [Berkrot]. SSRIs often carry warnings about suicide risks for children, teens and young adults.
    • Tricyclic antidepressants -- have largely been replaced because of side effects. The drugs work like SSRIs, but they block the reuptake of serotonin and norepinephrine. The class includes nortryptiline, amitriptyline and desipramine.
    • Selective norepinephrine reuptake inhibitors (SNRIs) -- block norepinephrine and serotonin reuptake. SNRIs include duloxetine and venlafaxine
    • Monoamine oxidase inhibitors (MAOIs) -- also have been largely replaced by safer drugs with fewer side effects; they prevent serotonin, norepinephrine or dopamine from being degraded in the brain. MAOIs include phenelzine, selegiline and tranylcypromine.

    There are several new approaches to treating depression. First, using antipsychotic drugs (aripriprazole, quetiapine) along with antidepressants enhances the effectiveness of the antidepressants. Ketamine, a drug that has been used for pain relief and anesthesia, may quickly increase the neurotransmitter glutamate and help prevent depressive patients from committing suicide. Agomelatine can increase melatonin and restore normal sleep patterns in depressive patients. Finally, triple reuptake inhibitors that boost all three neurotransmitters are being developed and tested [source: Tartakovsky].

    Zoloft, Paxil, and Prozac
    Zoloft, Paxil and Prozac are some of the most common antidepressants. (Jonathan Nourok/Getty Images)

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  2. Antidepressant drugs relieve the symptoms of depression. They work by trying to balance the levels of the body's neurotransmitters, which are chemicals that function in the parts of our brain that influence mood and emotion. Serotonin is such a neurotransmitter, and one kind of antidepressant drug works by increasing the concentration of serotonin in the nervous system. Other antidepressants work by restoring the levels of another neurotransmitter, norepinephrine. The regulation of an imbalance between these neurotransmitters, or the correction of a lack of them, can stabilize a person's mood and alleviate depression.

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