What Is a Longitudinal Study?

Table of ContentsView AllTable of ContentsThe Typical Longitudinal StudyExamplesTypesBenefitsPotential PitfallsFrequently Asked Questions

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Table of Contents

The Typical Longitudinal Study

Examples

Types

Benefits

Potential Pitfalls

Frequently Asked Questions

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A longitudinal study follows what happens to selectedvariablesover an extended time. Psychologists use the longitudinal study design to explore possible relationships among variables in the same group of individuals over an extended period.

Once researchers have determined the study’s scope, participants, and procedures, most longitudinal studies begin with baseline data collection. In the days, months, years, or even decades that follow, they continually gather more information so they can observe how variables change over time relative to the baseline.

For example, imagine that researchers are interested in themental health benefits of exercisein middle age and how exercise affects cognitive health as people age. The researchers hypothesize that people who are more physically fit in their 40s and 50s will be less likely to experience cognitive declines in their 70s and 80s.

Longitudinal vs. Cross-Sectional StudiesLongitudinal studies, a type ofcorrelational research, are usually observational, in contrast withcross-sectional research. Longitudinal research involves collecting data over an extended time, whereas cross-sectional research involves collecting data at a single point.

Longitudinal vs. Cross-Sectional Studies

Longitudinal studies, a type ofcorrelational research, are usually observational, in contrast withcross-sectional research. Longitudinal research involves collecting data over an extended time, whereas cross-sectional research involves collecting data at a single point.

To test this hypothesis, the researchers recruit participants who are in their mid-40s to early 50s. They collect data related to current physical fitness, exercise habits, and performance on cognitive function tests. The researchers continue to track activity levels and test results for a certain number of years, look for trends in and relationships among the studied variables, and test the data against their hypothesis to form a conclusion.

Psychology Research Jargon You Should Know

Examples of Early Longitudinal Study Design

Examples of longitudinal studies extend back to the 17th century, when King Louis XIV periodically gathered information from his Canadian subjects, including their ages, marital statuses, occupations, and assets such as livestock and land. He used the data to spot trends over the years and understand his colonies' health and economic viability.

In the 18th century, Count Philibert Gueneau de Montbeillard conducted the firstrecordedlongitudinal study when he measured his son every six months and published the information in “Histoire Naturelle.”

The Genetic Studies of Genius (also known as the Terman Study of the Gifted), which began in 1921, is one of the first studies to follow participants from childhood into adulthood. Psychologist Lewis Terman’s goal was to examine the similarities among gifted children and disprove the common assumption at the time that gifted children were “socially inept.”

Types of Longitudinal Studies

Longitudinal studies fall into three main categories.

An Overview of Psychology Research Methods

Benefits of Longitudinal Research

A longitudinal study can provide valuable insight that other studies can’t. They’re particularly useful when studying developmental and lifespan issues because they allow glimpses into changes and possible reasons for them.

For example, some longitudinal studies have explored differences and similarities among identical twins, some reared together and some apart. In these types of studies, researchers tracked participants from childhood into adulthood to see how environment influencespersonality, achievement, and other areas.

As with other types of psychology research, researchers must take into account some common challenges when considering, designing, and performing a longitudinal study.

Cost

Longitudinal studies require time and are often quite expensive. Because of this, these studies often have only a small group of subjects, which makes it difficult to apply the results to a larger population.

Selective Attrition

Participants sometimes drop out of a study for any number of reasons, like moving away from the area, illness, or simply losingmotivation. This tendency, known asselective attrition, shrinks the sample size and decreases the amount of data collected.

If the final group no longer reflects the originalrepresentative sample, attrition can threaten thevalidityof the experiment. Validity refers to whether or not a test or experiment accurately measures what it claims to measure. If the final group of participants doesn’t represent the larger group accurately, generalizing the study’s conclusions is difficult.

The World’s Longest-Running Longitudinal StudyLewis Terman aimed to investigatehow highly intelligent children developinto adulthood with his “Genetic Studies of Genius.” Results from this study were still being compiled into the 2000s. However, Terman was a proponent of eugenics and has been accused of letting his ownsexism,racism, and economicprejudiceinfluence his study and of drawing major conclusions from weak evidence.However, Terman’s study remains influential in longitudinal studies. For example, a recent study found new information on the original Terman sample, which indicated that men who skipped a grade as children went on to have higher incomes than those who didn’t.

The World’s Longest-Running Longitudinal Study

Lewis Terman aimed to investigatehow highly intelligent children developinto adulthood with his “Genetic Studies of Genius.” Results from this study were still being compiled into the 2000s. However, Terman was a proponent of eugenics and has been accused of letting his ownsexism,racism, and economicprejudiceinfluence his study and of drawing major conclusions from weak evidence.However, Terman’s study remains influential in longitudinal studies. For example, a recent study found new information on the original Terman sample, which indicated that men who skipped a grade as children went on to have higher incomes than those who didn’t.

A Word From Verywell

Longitudinal studies can provide a wealth of valuable information that would be difficult to gather any other way. Despite the typical expense and time involved, longitudinal studies from the past continue to influence and inspire researchers and students today.

Frequently Asked QuestionsA longitudinal study follows up with the same sample (i.e., group of people) over time, whereas a cross-sectional study examines one sample at a single point in time, like a snapshot.A longitudinal study can occur over any length of time, from a few weeks to a few decades or even longer.That depends on what researchers are investigating. A researcher can measure data on just one participant or thousands over time. The larger the sample size, of course, the more likely the study is to yield results that can be extrapolated.

A longitudinal study follows up with the same sample (i.e., group of people) over time, whereas a cross-sectional study examines one sample at a single point in time, like a snapshot.

A longitudinal study can occur over any length of time, from a few weeks to a few decades or even longer.

That depends on what researchers are investigating. A researcher can measure data on just one participant or thousands over time. The larger the sample size, of course, the more likely the study is to yield results that can be extrapolated.

7 SourcesVerywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Piccinin AM, Knight JE.History of longitudinal studies of psychological aging.Encyclopedia of Geropsychology.2017:1103-1109. doi:10.1007/978-981-287-082-7_103Terman L.Study of the gifted. In:The SAGE Encyclopedia of Educational Research, Measurement, and Evaluation.2018. doi:10.4135/9781506326139.n691Sahu M, Prasuna JG.Twin studies: A unique epidemiological tool.Indian J Community Med. 2016;41(3):177-182. doi:10.4103/0970-0218.183593Almqvist C, Lichtenstein P.Pediatric twin studies. In:Twin Research for Everyone. Elsevier; 2022:431-438.Warne RT.An evaluation (and vindication?) of Lewis Terman: What the father of gifted education can teach the 21st century.Gifted Child Q.2018;63(1):3-21. doi:10.1177/0016986218799433Warne RT, Liu JK.Income differences among grade skippers and non-grade skippers across genders in the Terman sample, 1936–1976.Learning and Instruction.2017;47:1-12. doi:10.1016/j.learninstruc.2016.10.004Wang X, Cheng Z.Cross-sectional studies: Strengths, weaknesses, and recommendations.Chest. 2020;158(1S):S65-S71. doi:10.1016/j.chest.2020.03.012Additional ReadingCaruana EJ, Roman M, Hernández-Sánchez J, Solli P.Longitudinal studies.J Thorac Dis. 2015;7(11):E537-E540. doi:10.3978/j.issn.2072-1439.2015.10.63

7 Sources

Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Piccinin AM, Knight JE.History of longitudinal studies of psychological aging.Encyclopedia of Geropsychology.2017:1103-1109. doi:10.1007/978-981-287-082-7_103Terman L.Study of the gifted. In:The SAGE Encyclopedia of Educational Research, Measurement, and Evaluation.2018. doi:10.4135/9781506326139.n691Sahu M, Prasuna JG.Twin studies: A unique epidemiological tool.Indian J Community Med. 2016;41(3):177-182. doi:10.4103/0970-0218.183593Almqvist C, Lichtenstein P.Pediatric twin studies. In:Twin Research for Everyone. Elsevier; 2022:431-438.Warne RT.An evaluation (and vindication?) of Lewis Terman: What the father of gifted education can teach the 21st century.Gifted Child Q.2018;63(1):3-21. doi:10.1177/0016986218799433Warne RT, Liu JK.Income differences among grade skippers and non-grade skippers across genders in the Terman sample, 1936–1976.Learning and Instruction.2017;47:1-12. doi:10.1016/j.learninstruc.2016.10.004Wang X, Cheng Z.Cross-sectional studies: Strengths, weaknesses, and recommendations.Chest. 2020;158(1S):S65-S71. doi:10.1016/j.chest.2020.03.012Additional ReadingCaruana EJ, Roman M, Hernández-Sánchez J, Solli P.Longitudinal studies.J Thorac Dis. 2015;7(11):E537-E540. doi:10.3978/j.issn.2072-1439.2015.10.63

Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Piccinin AM, Knight JE.History of longitudinal studies of psychological aging.Encyclopedia of Geropsychology.2017:1103-1109. doi:10.1007/978-981-287-082-7_103Terman L.Study of the gifted. In:The SAGE Encyclopedia of Educational Research, Measurement, and Evaluation.2018. doi:10.4135/9781506326139.n691Sahu M, Prasuna JG.Twin studies: A unique epidemiological tool.Indian J Community Med. 2016;41(3):177-182. doi:10.4103/0970-0218.183593Almqvist C, Lichtenstein P.Pediatric twin studies. In:Twin Research for Everyone. Elsevier; 2022:431-438.Warne RT.An evaluation (and vindication?) of Lewis Terman: What the father of gifted education can teach the 21st century.Gifted Child Q.2018;63(1):3-21. doi:10.1177/0016986218799433Warne RT, Liu JK.Income differences among grade skippers and non-grade skippers across genders in the Terman sample, 1936–1976.Learning and Instruction.2017;47:1-12. doi:10.1016/j.learninstruc.2016.10.004Wang X, Cheng Z.Cross-sectional studies: Strengths, weaknesses, and recommendations.Chest. 2020;158(1S):S65-S71. doi:10.1016/j.chest.2020.03.012

Piccinin AM, Knight JE.History of longitudinal studies of psychological aging.Encyclopedia of Geropsychology.2017:1103-1109. doi:10.1007/978-981-287-082-7_103

Terman L.Study of the gifted. In:The SAGE Encyclopedia of Educational Research, Measurement, and Evaluation.2018. doi:10.4135/9781506326139.n691

Sahu M, Prasuna JG.Twin studies: A unique epidemiological tool.Indian J Community Med. 2016;41(3):177-182. doi:10.4103/0970-0218.183593

Almqvist C, Lichtenstein P.Pediatric twin studies. In:Twin Research for Everyone. Elsevier; 2022:431-438.

Warne RT.An evaluation (and vindication?) of Lewis Terman: What the father of gifted education can teach the 21st century.Gifted Child Q.2018;63(1):3-21. doi:10.1177/0016986218799433

Warne RT, Liu JK.Income differences among grade skippers and non-grade skippers across genders in the Terman sample, 1936–1976.Learning and Instruction.2017;47:1-12. doi:10.1016/j.learninstruc.2016.10.004

Wang X, Cheng Z.Cross-sectional studies: Strengths, weaknesses, and recommendations.Chest. 2020;158(1S):S65-S71. doi:10.1016/j.chest.2020.03.012

Caruana EJ, Roman M, Hernández-Sánchez J, Solli P.Longitudinal studies.J Thorac Dis. 2015;7(11):E537-E540. doi:10.3978/j.issn.2072-1439.2015.10.63

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