Which of these is a characteristic sign of anxiety in postpartum blues?

Lack of sleep is indeed a characteristic sign of anxiety associated with postpartum blues. New mothers often experience heightened anxiety levels during the postpartum period due to the significant physical, emotional, and hormonal changes that occur after childbirth. This anxiety can lead to difficulties in sleeping, manifesting as insomnia or frequent awakenings throughout the night. Sleep disturbances can exacerbate feelings of worry and stress, further complicating the emotional state of new mothers as they adjust to their new role.

While a lack of appetite can also be a symptom of postpartum blues, it is more closely associated with depression rather than anxiety specifically. Feeling excessively happy or exhibiting calmness in difficult situations would not align with the anxiety symptoms that typically arise in postpartum blues, as these emotions generally indicate a positive emotional state, which contradicts the feelings of anxiety commonly experienced during this time.