**Core Concept**
Catatonia is a neuropsychiatric disorder characterized by a range of abnormal behaviors and motor symptoms, including immobility, rigidity, and mutism. It is often associated with severe mental illnesses such as schizophrenia, bipolar disorder, and major depressive disorder. The exact pathophysiology of catatonia is not fully understood, but it is thought to involve dysfunction in the brain's reward and stress systems.

**Why the Correct Answer is Right**
Catatonia is typically characterized by immobility, rigidity, and mutism, as well as other symptoms such as posturing, agitation, and echolalia. The motor symptoms of catatonia are thought to be related to abnormalities in the brain's dopamine and glutamate systems, which play a critical role in motor control and regulation. The treatment of catatonia often involves the use of benzodiazepines, which can help to rapidly improve symptoms by enhancing the activity of the neurotransmitter GABA.

**Why Each Wrong Option is Incorrect**
**Option A:** While hallucinations can occur in catatonia, they are not a defining characteristic of the disorder.
**Option B:** Catatonia can be associated with a range of affective symptoms, including depression and anxiety, but it is not primarily characterized by these symptoms.
**Option C:** While catatonia can occur in patients with schizophrenia, it is not exclusive to this disorder and can also be seen in patients with other psychiatric conditions.

**Clinical Pearl / High-Yield Fact**
Catatonia is a treatable condition, and prompt recognition and treatment can significantly improve outcomes. Benzodiazepines are often the first line of treatment for catatonia, and electroconvulsive therapy (ECT) may also be effective in some cases.

**Correct Answer: D.**