**Core Concept**
Lithium is a mood stabilizer used in the management of bipolar disorder. It helps to prevent episodes of mania and depression by modulating the activity of neurotransmitters, such as serotonin and dopamine, in the brain.

**Why the Correct Answer is Right**
Lithium works by inhibiting the reuptake of serotonin and dopamine, thereby increasing their availability in the synaptic cleft. It also has a neuroprotective effect, which may help to prevent the neuronal damage associated with bipolar disorder. Lithium's mechanism of action is closely related to its ability to modulate the activity of the enzyme inositol monophosphatase, which is involved in the signaling pathway of the second messenger inositol trisphosphate.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because lithium is not primarily used for the treatment of unipolar depression. While it may be used as an adjunctive therapy in certain cases, it is not a first-line treatment for major depressive disorder.
**Option B:** This option is incorrect because lithium is not used for the treatment of schizophrenia. Antipsychotic medications, such as haloperidol and risperidone, are typically used to manage symptoms of schizophrenia.
**Option C:** This option is incorrect because lithium is not used for the treatment of anxiety disorders. Benzodiazepines, such as alprazolam and clonazepam, are commonly used to manage symptoms of anxiety.

**Clinical Pearl / High-Yield Fact**
Lithium's therapeutic window is very narrow, and levels above 1.5 mmol/L can increase the risk of toxicity. It is essential to monitor lithium levels regularly in patients taking this medication.

**Correct Answer:** C.