Insomnia and Serotonin

Insomnia and serotonin could have a loose linkage based on serotonin’s action within the brain as well as known side effects of drug therapy targeting serotonin pathways.

Insomnia is a sleep disorder resulting in a person’s inability to fall asleep or that they cannot stay asleep for a decent length of time. These people experience little or no stage 4 or REM sleep and rarely feel rested.

Serotonin is a neurotransmitter found extensively through the brain and nervous system.  It is secreted by neurons in an area of the brainstem known as the Raphe nucleus and acts on a variety of excitatory and inhibitory receptors. 

It is the action of serotonin on the receptors in the sleep areas of the brain that imply a link between insomnia and serotonin.  In laboratory experiments, insomnia and serotonin were linked when reduction in serotonin levels was shown to eliminate sleep.

Injection of serotonin at specific locations in the brainstem induced sleep.  However, linking insomnia and serotonin in drug trials using serotonin precursors was unsuccessful.

Insomnia and Serotonin

Selective Serotonin Reuptake Inhibitors (SSRIs) are a class of drugs used to treat different forms of depression.  This class of drug reinforces the suspected link between insomnia and serotonin.  SSRIs function to block the reuptake of serotonin after it has been released into the brain.  This effectively prolongs the effects of serotonin which could mimic an injection of excess serotonin as was performed in the lab experiments linking insomnia and serotonin.  One of the recognized side effects of SSRIs is insomnia.  Insomnia does not affect all people taking SSRIs and rates of insomnia vary depending on the administered drug.  

Currently, signs indicate that prolonged action of this neurotransmitter causes sleeplessness.  The pathway describing the interaction between insomnia and serotonin is still unknown.