Which of the following is NOT a side effect commonly experienced by patients?

The correct answer is related to the effects experienced by patients in relation to medications or medical treatments. In the context of pharmacology, drugs often produce side effects that can lead to symptoms such as drowsiness, anorexia, and constipation. These are recognized as potential adverse effects of many medications.

Drowsiness is a common side effect, particularly with medications that act on the central nervous system, such as sedatives or certain pain medications. Anorexia, or loss of appetite, is also frequently seen with certain medications, especially some antidepressants, chemotherapy agents, and those affecting gastrointestinal function. Constipation emerges as a side effect with various medications, including opioids and some antidepressants, which can alter gut motility.

In contrast, improved mood is generally not classified as a side effect in this context. It is more an intended outcome of specific therapeutic interventions, especially for drugs designed to alleviate depression or anxiety. Therefore, while negative side effects can significantly impact a patient's well-being, improved mood is typically viewed as a positive therapeutic effect rather than a side effect, making it the correct choice for this question.