Which of the following medications is commonly prescribed as a mood stabilizer?

Lithium is widely recognized as a primary mood stabilizer used in the treatment of bipolar disorder and other mood disorders. It works by modulating neurotransmitters in the brain, which helps to stabilize mood and reduce the frequency and severity of mood swings, including both manic and depressive episodes. Its effectiveness in preventing manic episodes and reducing the risk of suicidality in individuals with mood disorders makes it a cornerstone in the pharmacological management of these conditions.

Other medications may play roles in mood regulation or management of specific symptoms but are categorized differently. For example, Sertraline and Fluoxetine are primarily selective serotonin reuptake inhibitors (SSRIs) that focus on treating depression and anxiety rather than stabilizing mood. Aripiprazole is an atypical antipsychotic that can be used as an adjunct treatment for mood stabilization in some cases, particularly in combination with other medications, but it is not primarily classified as a mood stabilizer itself. Hence, when considering the mainstay for mood stabilization, Lithium stands out as the most appropriate choice.