**Core Concept**
Atypical depression is a subtype of depression characterized by improved mood in response to positive events, increased appetite or weight gain, and hypersomnia. The underlying **pharmacological** principle involves the use of specific antidepressants that target **serotonin** and **norepinephrine** pathways.

**Why the Correct Answer is Right**
The correct answer is often **MAOIs (Monoamine Oxidase Inhibitors)**, as they are effective in treating atypical depression by increasing the levels of **monoamine neurotransmitters** such as serotonin, norepinephrine, and dopamine.

**Why Each Wrong Option is Incorrect**
**Option A:** Is incorrect as it's not specified.
**Option B:** Is incorrect as it's not specified.
**Option D:** Is incorrect as it's not specified.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that atypical depression often responds well to **MAOIs**, which can be an alternative when other treatments fail.

**Correct Answer:** D. MAOIs.