Which of the following is a side effect of opiate withdrawal?

Opiate withdrawal can lead to a variety of physical and psychological symptoms as the body reacts to the absence of the substance it has become accustomed to. One of the notable side effects experienced during opiate withdrawal is muscle aches. This occurs because opiates can impact the body's ability to regulate pain and muscle tension. When the opiates are no longer present, individuals often report significant discomfort and pain in their muscles, which can be quite distressing and may contribute to the overall withdrawal experience.

The other choices, while they may seem plausible in different contexts, do not accurately represent common side effects of opiate withdrawal. Increased energy and enhanced mood are typically not associated with withdrawal, as the process often leads to fatigue and dysphoria instead. Weight gain is also not a common side effect; in fact, many individuals may experience weight loss during withdrawal due to decreased appetite and other physical symptoms.