**Core Concept**
Maintenance therapy in uncomplicated bipolar disorder aims to prevent relapse of manic or depressive episodes. The chosen medication should have a favorable risk-benefit profile, be effective for both manic and depressive phases, and have a low side-effect burden.

**Why the Correct Answer is Right**
Lithium is the drug of choice for maintenance therapy in uncomplicated bipolar disorder due to its efficacy in preventing relapse of both manic and depressive episodes. It acts by inhibiting inositol monophosphatase, which is involved in the phosphoinositide signaling pathway. This leads to a decrease in intracellular cyclic AMP levels, which in turn reduces the activity of various neurotransmitter systems, including dopamine and serotonin. Lithium also has a mood-stabilizing effect by modulating the activity of GABA and glutamate.

**Why Each Wrong Option is Incorrect**
**Option A:** Valproate is an alternative mood stabilizer but is not the first-line treatment due to its higher side-effect burden and potential for hepatotoxicity.
**Option B:** Carbamazepine is an anticonvulsant that can be used in bipolar disorder but is not as effective as lithium for long-term maintenance and has a higher risk of adverse effects.
**Option C:** Lamotrigine is primarily used for the maintenance treatment of bipolar depression but is not the first-line treatment for overall maintenance therapy in bipolar disorder.

**Clinical Pearl / High-Yield Fact**
Lithium levels should be monitored regularly, especially in patients with pre-existing kidney or thyroid disease, as it can cause nephrogenic diabetes insipidus and hypothyroidism.

**Correct Answer:** C.