Which of the following is a common side effect of antidepressants?

Many antidepressants are associated with gastrointestinal side effects, and an upset stomach is one of the most commonly reported issues among individuals starting antidepressant therapy. These medications can influence the chemical balance in the brain, which also affects the digestive system, leading to symptoms such as nausea, diarrhea, or general stomach discomfort.

In contrast, while memory loss, severe anxiety, and weight loss can occur in some individuals during treatment, they are not as universally recognized or common side effects. Memory loss can be influenced by various factors and isn't a typical response to antidepressants specifically. Severe anxiety may be a symptom underlying the reason for treatment but isn't usually induced by the medications themselves, and weight loss isn't an expected outcome for most users of antidepressants, particularly since some may actually gain weight. Therefore, experiencing an upset stomach is a well-documented and frequent side effect when starting or adjusting antidepressant medication.