What is the primary use of Lithium in medication?

Lithium is primarily utilized in the management of manic symptoms associated with bipolar disorder, making it a cornerstone treatment for this condition. As a mood stabilizer, Lithium helps to regulate mood swings, reducing the intensity and frequency of manic episodes. This efficacy in stabilizing mood is crucial for individuals with bipolar disorder, as it addresses both the manic and depressive phases of the illness.

The drug's exact mechanism of action remains partially understood, but it is believed to influence neurotransmitter systems in the brain, affecting the way in which cells respond to various stimuli. This stabilizing effect is critical, especially during manic or hypomanic episodes, which can lead to risky behavior, impaired judgment, and other serious consequences if left untreated.

In contrast, the other options do not reflect the primary therapeutic use of Lithium. For example, while insomnia and anxiety may be addressed with various medications, they are not the intended use of Lithium. Additionally, while pain relief is an important aspect of clinical medicine, Lithium is not prescribed for this purpose. Hence, its classification as a treatment for bipolar disorder underscores its unique role in psychiatric care.