**Core Concept**
Pseudo-Cushing's syndrome refers to a condition that mimics the clinical and biochemical features of Cushing's syndrome, but is not caused by excessive cortisol production from an adrenal or pituitary source. This condition can be caused by various factors, including psychiatric disorders, medications, and other medical conditions.

**Why the Correct Answer is Right**
Pseudo-Cushing's syndrome is often seen in patients with severe psychiatric disorders, such as major depressive disorder or schizophrenia. The mechanism behind this is not fully understood, but it is thought to be related to the body's response to chronic stress and the associated changes in cortisol production. In these patients, the cortisol levels may be elevated in response to the stress, but it is not due to an underlying endocrine disorder.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because pseudo-Cushing's syndrome is not typically associated with primary adrenal insufficiency. While adrenal insufficiency can cause changes in cortisol levels, it is not a cause of pseudo-Cushing's syndrome.
**Option B:** This option is incorrect because pseudo-Cushing's syndrome is not typically associated with thyroid disorders. While thyroid disorders can affect cortisol levels, they are not a common cause of pseudo-Cushing's syndrome.
**Option C:** This option is incorrect because pseudo-Cushing's syndrome is not typically associated with polycystic ovary syndrome (PCOS). While PCOS can cause hormonal imbalances, it is not a cause of pseudo-Cushing's syndrome.

**Clinical Pearl / High-Yield Fact**
It is essential to differentiate pseudo-Cushing's syndrome from true Cushing's syndrome, as the management and treatment of these conditions differ significantly. A high index of suspicion and a thorough evaluation, including laboratory tests and imaging studies, are necessary to diagnose pseudo-Cushing's syndrome.

**Correct Answer:** D.