Longitudinal Study Cross sectional Study

Longitudinal Study vs. Cross-sectional Study
Author’s Name
Institutional Affiliation

Longitudinal Study vs. Cross-sectional Study
Circumstances
A researcher can prefer longitudinal research to a cross-sectional study when he wants to conduct repetitive observational research on a single subject over an extended time, say ten years. A researcher can also choose a longitudinal study when analyzing a cause and effect relationship among variables over time because it provides patterns and correlations efficiently. A longitudinal study is also preferable to cross-sectional research when one wants to examine developmental trends, for instance, across lifespans (Caruana, Roman, Hernández-Sánchez, & Solli, 2015). Unlike the longitudinal study, where study variables can change over time, the cross-sectional study is done in one instance with all study variables of the research subjects remaining constant throughout.
Advantages and Disadvantages
Both longitudinal and cross-sectional studies have their advantages and disadvantages. The first advantage of a longitudinal study is that it allows the researcher to identify and correlate events to specific exposures and determine patterns, chronicity, and timing (Caruana et al., 2015). For example, one can easily explain the pattern or trends of Down syndrome in Children by studying them longitudinally from their birth to their later years. The second advantage of a longitudinal study is that the accuracy of data collection is virtually always high because the gathering of information is done in real-time using observations.

However, two disadvantages of this study design are: 1) it takes an extremely long time to yield results and researchers involved may miss seeing the comprehensive outcome of the study, and 2) it comes with a high degree of unpredictability since it involves the same subject(s) for a prolonged period. Therefore, if something happens to the subject or if participants drop in the course of the study, the entire research is flagged.
Advantages of a cross-sectional study are: 1) it provides one with the ability to compare various population groups at the same and 2) it is generally easier, quicker, and cheaper to undertake (Sedgwick, 2014). Cross-sectional research uses questionnaire surveys, which do not need to be repeated over time. However, one downside of cross-sectional studies is their increased susceptibility to non-response bias, for instance, if the subjects who agreed to participate in the research are different from those who turned down, giving a sample that is non-representative of the actual population. Also, this kind of study cannot be employed in prolonged or long-term research project because of its one-off nature.
Research Question
An example of a research question that can be addressed using a longitudinal study is “What is the long-term effect of Marijuana on brain functionality?” This question suffices because it requires trend, pattern, cause and effect analysis which can be done best using longitudinal research.

References
Caruana, E. J., Roman, M., Hernández-Sánchez, J., & Solli, P. (2015). Longitudinal studies. Journal of Thoracic Disease, 7(11), E537–E540. http://doi.org/10.3978/j.issn.2072-1439.2015.10.63Sedgwick, P. (2014). Cross-sectional studies: Advantages and disadvantages. BMJ: British Medical Journal (Online), 348. doi: https://doi.org/10.1136/bmj.g2276