**Core Concept**
Pathological gambling is a type of behavioral addiction that was previously excluded from the Diagnostic and Statistical Manual of Mental Disorders (DSM) but is now recognized as a mental health disorder. The inclusion of pathological gambling in DSM-5 reflects a growing understanding of the underlying neurobiological mechanisms and the significant impact it has on an individual's quality of life.

**Why the Correct Answer is Right**
The correct answer is related to the reclassification of substance-related and addictive disorders in DSM-5. Pathological gambling was reclassified as a gambling disorder, which is a type of behavioral addiction. This change reflects the understanding that gambling disorder shares common underlying neurobiological mechanisms with substance use disorders, such as reward processing and impulsivity. The inclusion of gambling disorder in DSM-5 acknowledges the significant distress and impairment it can cause in an individual's life.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because pathological gambling is not a type of anxiety disorder. While individuals with pathological gambling may experience anxiety related to their behavior, it is not classified as an anxiety disorder.
* **Option B:** This option is incorrect because pathological gambling is not a type of personality disorder. While personality disorders may co-occur with pathological gambling, it is not classified as a personality disorder.
* **Option C:** This option is incorrect because pathological gambling is not a type of sleep disorder. While sleep disturbances may be a co-occurring issue in individuals with pathological gambling, it is not classified as a sleep disorder.

**Clinical Pearl / High-Yield Fact**
It's essential to recognize that behavioral addictions, such as gambling disorder, can have a significant impact on an individual's quality of life and relationships. Clinicians should be aware of the signs and symptoms of behavioral addictions and provide comprehensive treatment that addresses the underlying neurobiological mechanisms.

**Correct Answer:** C. Gambling Disorder