Which medication is primarily used to stabilize mood in bipolar disorder?

Lithium is established as the primary medication for stabilizing mood in individuals with bipolar disorder. This medication works by influencing the flow of sodium through nerve and muscle cells, which helps to balance mood swings that are characteristic of the disorder. Its effectiveness in reducing the frequency and severity of manic and depressive episodes has been supported by extensive clinical research, making it a cornerstone in the treatment of bipolar disorder.

In contrast, the other medications listed are primarily used for treating depressive symptoms rather than stabilizing mood specifically in bipolar disorder. Escitalopram and fluoxetine are selective serotonin reuptake inhibitors (SSRIs) primarily used for depression and anxiety disorders. Although they can be prescribed alongside mood stabilizers for individuals with bipolar disorder, they are not primarily aimed at mood stabilization. Venlafaxine is an SNRI (serotonin-norepinephrine reuptake inhibitor) also used in treating major depressive disorder and general anxiety disorder, but it does not have the specific mood-stabilizing properties that lithium possesses. Therefore, lithium is uniquely suited for mood stabilization in bipolar disorder, distinguishing it from the other options.