What is a Longitudinal Study?

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  • Written By: D. Jeffress
  • Edited By: Bronwyn Harris
  • Last Modified Date: 04 October 2019
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A longitudinal study is a research project that involves the observation of one or more sample groups over a long time, anywhere from a few months to 30 years or more. Such studies are invaluable to social science; they allow researchers to track changes and trends in individual behavior, societal development, relationships, and many other variables. A longitudinal study might be conducted by psychologists, sociologists, medical researchers, environmental scientists, anthropologists, or other experts who want to obtain reliable information about a population over time.

Longitudinal studies are especially important to research psychologists and sociologists who want to learn about correlations and trends in human behavior. A research psychology team might, for example, wish to find out if children of alcoholics are more likely than other children to develop behavioral problems and alcoholism later in life. The team would select a large population of very similar children, such as four-year-old males with alcoholic fathers in a given city. Researchers might interview the children, their parents, and their teachers annually over a period of 20 years, recording answers in the same manner each year. After the longitudinal study period, the researchers would organize data on each child and look for correlations in the results to determine if predictions can be made about other children of alcoholics.


Researchers have discovered many benefits of conducting longitudinal studies over laboratory experiments and short-term clinical trials. A longitudinal study allows scientists to observe changes in people as they live in the real world, interact with others, experience struggles, and enjoy successes. Using a longitudinal study research team can get a better idea of how a certain inherited disease, such as cystic fibrosis, affects people over the course of their lives. Longitudinal studies are also effective at tracking societal conditions, such as poverty rates, over several decades so that new public policies can be developed.

There are certain cases, however, when longitudinal studies are less accurate than direct, clinical experiments and trials. A pharmaceutical company that wants to test a new drug would likely conduct several clinical trials with many different sample groups instead of observing a single group of participants over time. The company would want to learn about immediate reactions and side effects during a controlled experiment to determine whether or not the drug is safe to market commercially. A longitudinal study simply introduces too many variables to pinpoint the effectiveness of a drug. Participants might not take the recommended doses, undergo positive or negative lifestyle changes, or report inaccurate information to researchers.


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Post 2

I once participated in a drug study. I went to a facility and was given the medication. I then had a form which I used to record any side effects I had.

Our group leader later said that since all of us in the study had MS, that the study was also known as a cross-sectional study. I have never heard of that before. She said it referred to the fact that we all have an illness, and we were being monitored over a period of time.

All I know is that in the end, I got paid for my participation and I found the experience to be rewarding. Not only did I receive treatment, but I helped others by recording my experiences with the drug.

Post 1

A really fun way to check out a longitudinal study is to watch the British documentary "Up." It follows a group of British people from early childhood onward with the hypothesis that a person's social class will likely remain the same throughout their entire life. The researchers interview the participants every seven years. It's also an interesting insight into British culture in the 1960's. The study is still going on today with the next set of interviews scheduled for this year.

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