**Core Concept**
Deep brain stimulation (DBS) is a neurosurgical procedure that involves implanting an electrode in a specific area of the brain to modulate abnormal brain activity. DBS has been FDA-approved for several indications, including movement disorders and obsessive-compulsive disorder (OCD).

**Why the Correct Answer is Right**
Major depression is not an FDA-approved indication for deep brain stimulation. While DBS has been used off-label for treating treatment-resistant depression, the FDA has not cleared it for this specific indication. The FDA approval process involves rigorous clinical trials to demonstrate safety and efficacy. In the case of DBS for depression, more research is needed to establish its benefits and risks.

**Why Each Wrong Option is Incorrect**
**Option A:** OCD is an FDA-approved indication for DBS, particularly for patients who have not responded to other treatments. DBS targets the anterior limb of the internal capsule or the ventral anterior limb of the internal capsule to modulate the hyperactive circuitry in OCD.
**Option C:** Parkinsonism is an FDA-approved indication for DBS, which targets the subthalamic nucleus (STN) or the globus pallidus internus (GPi) to alleviate motor symptoms such as tremor, rigidity, and bradykinesia.
**Option D:** Dystonia is also an FDA-approved indication for DBS, which targets the globus pallidus internus (GPi) to alleviate dystonic postures and movements.

**Clinical Pearl / High-Yield Fact**
When considering DBS for psychiatric indications, it's essential to note that the procedure is typically reserved for patients with treatment-resistant conditions who have not responded to other therapies. DBS requires a multidisciplinary team approach, including psychiatrists, neurologists, and neurosurgeons.

✓ Correct Answer: B. Major depression.