Final answer:
Comparing the health of drug users to nonusers in studies poses a problem because it can be challenging to isolate the drug as the only factor affecting health differences. Observational studies can only show correlations and cannot control all variables as in experimental designs. Researchers cannot ethically conduct controlled experiments on the long-term effects of harmful substances like cigarette smoke.
Step-by-step explanation:
Most studies of the health hazards associated with particular drugs compare the health of known drug users with that of nonusers. This poses a problem because these studies typically involve observational research where variables cannot be controlled in the same manner as an experimental design. A major issue with this type of comparison is that it can be difficult to isolate the drug as the sole factor responsible for any observed health differences. Drug users may have other underlying health problems or lifestyle factors that contribute to their health outcomes, which may not be present in the nonuser group. Moreover, observational studies can only show correlations, not causations, making it challenging to determine if the drug use is actually causing the health issues.
In the realm of pharmaceutical testing, such as observing the long-term effects of cigarette smoking on lung cancer, conducting controlled experiments by exposing people to harmful substances is not ethical. Therefore, researchers rely on observational studies, but these have limitations in proving causation and may sometimes only show correlation. The variables in people's lives are diverse, and not all can be controlled in an observational study. In addition, these studies often deal with health related events, observational research, and the challenges of drawing conclusions about drug efficacy and safety.