Which of the following is a withdrawal symptom of opioids?

Muscle pain is a well-documented withdrawal symptom of opioids. When an individual who has been using opioids suddenly reduces their intake or stops altogether, their body reacts to the absence of the drug, leading to a variety of physical and psychological symptoms. This phenomenon is part of the body's adjustment process to the lack of external opioids, which may have previously suppressed pain sensations. As a result, individuals often experience heightened sensitivity to pain, muscle aches, and general discomfort when withdrawing from opioids.

Additionally, the other options do not align with the expected withdrawal symptoms from opioids. Increased appetite and improved mood typically do not occur during withdrawal; rather, individuals might experience loss of appetite and mood disturbances, such as anxiety or depression. Likewise, while energy levels may fluctuate, withdrawal is more likely to lead to fatigue and lethargy rather than an increase in energy. This context underscores why muscle pain is the correct symptom associated with opioid withdrawal.