How Antidepressants Work?

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Antidepressants are type of medications that change certain natural neurochemicals in our brains. Due to this mechanism they are effective against depression, obsessive compulsive disorders, anxiety disorders and chronic pain syndromes (Fibromyalgia etc).

What causes depression?

According to the current hypothesis, depression is caused by an imbalance in brains own neurotransmitters and related neuronal changes. Most antidepressants acts by increasing the deficient neurotransmitters.


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What are the types of anti-depressants available?

There are numerous types of anti-depressants available in the market. They work in different ways and most common types are SSRIs (Selective serotonin reuptake inhibitors), Tricyclic anti-depressants, MAOI (Mono amine oxidase inhibitors), SNRI (Selective noradrenalin and serotonin reuptake inhibitors), SARI (Serotonin antagonist and reuptake inhibitors), DRIs (Dopamine reuptake inhibitors), Alpha 2 adrenergic blockers and NRIs (Noradrenalin reuptake inhibitors).

Even though each drug acts differently, they all increase the serotonin, noradrenalin and dopamine levels in certain brain areas. Most drugs increase one or more of above naturally occurring neurochemicals.

They increase the levels by inhibition of reuptake of the above neurochemicals by the neurons, by way of inhibiting reuptake pumps. In addition, Alpha 2 adrenergic blockers increase above levels by blocking Alpha 2 adrenergic receptor which functions as a part of feedback loop.

How increased serotonin treats depression?

Most anti-depressants increase serotonin levels in the brain. This causes various adaptive changes in the synapses of the brain. These changes results in modification of synapses and neurons inside the brain. They ultimately treats depression and other related diseases that are mentioned above. Some of the adaptive changes are down regulation of serotonin auto receptors and gene expression which leads to increased synthesis of certain proteins.

MAOIs, SSRIs, TCAs, SNRIs, SARIs, and Alpha 2 adrenergic receptor blockers increase the serotonin levels in the brain regions.

Common examples of above drugs

MAOI – Moclobomide

SSRI – Fluoxetine (Prozac)

TCAs – Amitriptyline (Elavil)

SNRIs – Venlafaxine (Effexor)

SARIs – Trazadone

Alpha 2 adrenergic blockers – Mirtazapine

What are the other mechanisms of anti-depressants?

Apart from increasing serotonin levels in the brain some anti-depressants increase dopamine and noradrenalin levels. NRIs such as Raboxetine increase the noradrenalin levels without increasing other neurotransmitters. DRIs such as Buproprion have significant dopamine reuptake inhibition property.

Increased noradrenalin levels and dopamine levels cause several adaptive changes inside the neurons and it treats depression. In addition, increased dopamine levels cause increased energy levels. It is because; it acts as the final common pathway in pleasure. Dopamine is the main actor in brains reward system.

Summary

Antidepressants are commonly prescribed for various mental health problems. They act via brains natural neurotransmitter system. Almost all drugs acts by increasing serotonin, noradrenalin and dopamine levels in the body. They ultimately causes adaptive changes in neurons responsible for the causation of depression.

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