**Core Concept**
Delirium is a complex neuropsychiatric syndrome characterized by acute onset of fluctuating cognitive impairment, inattention, and altered level of consciousness. It is often associated with underlying medical conditions, medications, or environmental factors.

**Why the Correct Answer is Right**
Delirium is a multifactorial disorder involving disruptions in normal neurotransmitter function, particularly affecting the cholinergic and dopaminergic systems. The pathophysiology involves impaired neurotransmission, decreased acetylcholine release, and altered GABAergic activity. This results in cognitive dysfunction, disorganized thinking, and altered level of consciousness.

**Why Each Wrong Option is Incorrect**
**Option A:** This option might be incorrect if it contradicts the core concept of delirium as a multifactorial disorder or misrepresents its pathophysiology.

**Option B:** This option might be incorrect if it suggests that delirium is solely caused by a single factor, such as medication side effects, or neglects the role of underlying medical conditions.

**Option C:** This option might be incorrect if it implies that delirium is a normal part of aging or a benign condition, rather than a serious neuropsychiatric syndrome requiring prompt evaluation and management.

**Clinical Pearl / High-Yield Fact**
Delirium is often remembered by the mnemonic "CAM-I-CARE," which stands for **C** onfusion, **A** ltered **M** indset, **I** nattention, **C** onsciousness, **A** ltered **R** eality testing, and **E** motion and **C** ommunication disturbances.

**Correct Answer:** None of the above options are correct, as the question asks for the options that are "all except."