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The Effects of Serotonin and Norepinephrine in Depression

Serotonin and norepinephrine are two neurotransmitters that are involved in mood, and are thought to be connected to depression. The Mayo Clinic notes that it is hypothesized that a deficit in either neurotransmitter can cause depression. Both serotonin and norepinephrine are targeted in antidepressants, which are intended to relieve depression symptoms.

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Serotonin's Role

The first claims that a deficit of serotonin is the cause of depression. Evidence that supports this hypothesis is that a deficit of serotonin correlates to symptoms of depression, such as:

  • low mood
  • cognitive problems
  • sexual dysfunction
  • sleeping problems
  • decreased activity
  • increased suicidal thoughts

The authors add that patients with major depression have a decreased amount of L-TRP, the precursor of serotonin, compared to non-depression patients. The second is a more moderate hypothesis, stating that the deficit of serotonin increases the patient's vulnerability to depression.

Norepinephrine's Role

Norepinephrine is also hypothesized to be involved in depression, and is synthesized from dopamine, another mood neurotransmitter. P.L. Delgato and F.A. They hypothesize instead that while norepinephrine is involved in depression, it is due rather to a dysfunction of a brain area where norepinephrine is present.

Antidepressants

The mechanism of reuptake inhibitor antidepressants is to prevent the brain from recycling the neurotransmitter, like serotonin or norepinephrine; this leaves more for the brain to use, thus improving the patient's mood 1. The Mayo Clinic adds that antidepressants are also neuroprotective: “Antidepressants may increase the effects of brain receptors that help nerve cells keep sensitivity to glutamate--an organic compound of a nonessential amino aci--in check.” By lowering the nerve cells' glutamate sensitivity, it prevents overwhelming the areas of the brain involved in depression. With antidepressants, the patient can use a selective reuptake inhibitor, like an SSRI or selective norepinephrine reuptake inhibitor, that targets only one neurotransmitter. A dual reuptake inhibitor, like an SNRI, targets both serotonin and norepinephrine, which may provide better results if the depression results from problems with both neurotransmitters 1.

The Wrap Up

Serotonin and norepinephrine are two neurotransmitters that are involved in mood, and are thought to be connected to depression. By lowering the nerve cells' glutamate sensitivity, it prevents overwhelming the areas of the brain involved in depression. A dual reuptake inhibitor, like an SNRI, targets both serotonin and norepinephrine, which may provide better results if the depression results from problems with both neurotransmitters').

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