What type of study design compares the same group's experiences when they receive and do not receive a drug?

The most appropriate study design for comparing the same group's experiences when they receive a drug versus when they do not is the cross-over study design. In a cross-over study, participants are exposed to both treatments—in this case, the drug and a placebo or no drug—at different times. This allows researchers to observe the effects of the drug on the same individuals, providing valuable insight into how each participant responds to each condition.

This design is particularly advantageous because it controls for inter-subject variability; since each participant acts as their own control, variability is minimized. This leads to potentially more accurate and reliable results regarding the drug's efficacy and safety, as responses can be directly compared within the same subjects.

In contrast, the other study designs mentioned do not allow for this direct comparison of the same individuals receiving different treatments. For example, cross-sectional studies assess data at one point in time and do not lend themselves to comparing different treatments over time in the same subjects. Longitudinal studies analyze data collected over time but typically involve separate groups for each condition. Nested case-control studies focus on factors associated with a particular outcome rather than directly comparing treatments within the same cohort. Thus, the cross-over design is specifically tailored to the requirements of this question.