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Lather, rinse, repeat: The importance of long-term studies in autism

Cheryl Cohen
Online Community Director
Interactive Autism Network (IAN)
Date Published: 
July 25, 2014

The way that researchers design their research studies is often determined by what a researcher wants to learn, his/her training and expertise, and the types of funding that are available. Longitudinal studies observe and measure a phenomenon over time in a particular set of people. This type of study may last many years and can be quite costly. It allows scientists to understand changes that occur at an individual level and at a group level and helps scientists disentangle the effects of history (for example, a person with autism born in 1970 will experience a very different world than someone born in 2014), identify critical periods for exposure and risks by allowing scientists to look at sequences (did the anxiety disorder occur before or after the bullying?), and can help scientists pry apart whether one phenomenon (scientists call them variables) causes another.

Some important longitudinal studies in medicine

One of the best known longitudinal studies in medicine is the Framingham Heart Study. This study on cardiovascular disease (CVD) began in 1948, when 5,209 adults in the town of Framingham, Massachusetts were recruited by researchers “to identify the common factors or characteristics that contribute to CVD by following its development over a long period of time in a large group of participants who had not yet developed overt symptoms of CVD or suffered a heart attack or stroke.”1 Participants returned to the study every two years and had detailed medical examinations. In 1971, the children of the original participants joined the study. And now the grandchildren are participating along with others from the community. With over 2,000 peer-reviewed publications, the Framingham study has contributed tremendously to our understanding of heart disease and a number of other chronic conditions. For example, in 1960, evidence from the Framingham Study revealed that cigarette smoking increased the risk of heart disease. In 1961, cholesterol levels, high blood pressure, and electrocardiogram abnormalities joined the culprits.2 Important knowledge that seems like common sense to us now was made possible by this study.

Another important study in medicine is the Nurses’ Health Study (NHS), which began recruiting its first group of women (called a cohort) in 1976. It gathers medical and lifestyle information from female nurses in the U.S. focusing on the prevention of cancer. A second group began forming in 1989 (NHS2). In 2011, the third group (NHS3), began recruiting from the U.S. and Canada. This group now has 38,000 individuals registered. Like IAN, the NHS3 study is done entirely online with participants completing one thirty-minute survey every six months. Over the years, 230,000 female nurses have participated, with 90% of the nurses from the original 1976 group still participating. Without the NHS, we might not understand that by exercising more, women can decrease their chances of getting cardiovascular disease, colon cancer, and breast cancer.3

The Nurses’ Health Study and autism

While longitudinal studies like the NHS are designed to focus on factors related to particular health-related conditions (cancer, in the case of the NHS), the participants of the NHS2 and the information collected about them has also been used to learn about other factors that influence their health. Recently, John Constantino, a noted autism researcher, worked with participants from the NHS2 who had children with ASD. He used a standardized questionnaire to learn whether the parents had some autistic traits themselves. His research showed that parents of children with autism are more likely to have autistic traits than parents of neurotypical children.4

Why are longitudinal studies in autism important?

Adolescents and Adults with Autism is one of the most compelling longitudinal studies about autism. It began in 1998 when researchers recruited more than four hundred families with family members with ASD from Wisconsin and Massachusetts. The study’s goals were to “describe the quality of life of these families, assess the extent to which their service needs are adequately met, and to examine the plans they made and put into place for the future.”5 This long-term approach allowed the researchers to see how the families were doing over time and to figure out what factors contribute to their quality of life. The study has produced numerous academic publications as well as family-friendly ones. Families participated in two or three hour interviews at 18 month intervals over the course of 14 years.6

According to autism researcher Julie Lounds Taylor, who has published important research about the Adolescents and Adults with Autism study:

“Longitudinal studies are critical in autism research because they can answer many questions that cannot adequately be addressed any other way. For example, do the benefits of treatments in early childhood last into adulthood? What is the natural course of autism through the lifespan? Does the behavioral profile tend to get better over time, stay the same, or worsen? Do difficulties in employment tend to abate over time or worsen? And for whom? These are very important questions that have significant implications for people with autism and their families, and longitudinal research gives us the best tools to be able to answer them.”7

A long look at infants and toddlers

There are many other longitudinal studies in autism, especially ones that look at infants and toddlers. The High Risk Baby Siblings Research Consortium is a network of projects that follows the younger brothers and sisters of children with autism through their early years (usually age 3). As of 2012, their database consisted of information from 2,838 high-risk siblings and 1,703 low-risk controls.8  Included in the findings is the important finding that girls are widely underdiagnosed9, the younger brothers and sisters of children with autism are more likely to have social and communication delays, including autism spectrum disorder than siblings of unaffected children.10 Learn more about research on high risk baby siblings.

This type of study allows researchers to trace the characteristics of people before they are diagnosed, leading to techniques that allow us to diagnose autism earlier and earlier and to characterize different traits.11 While these baby siblings studies usually start between the ages of six and eighteen months, The Early Autism Risk Longitudinal Investigation (EARLI study) has recruited nearly 1,200 mothers at four locations in the United States. It follows mothers through pregnancy and delivery and follows their new babies through the third year of the babies’ lives. This study is designed to examine what causes autism by looking at environmental risk factors for autism and their potential interaction with genes.12  It is hoped that the EARLI studies and others like it will help “identify avoidable or modifiable factors” and “help reduce the impact of autism on quality of life.”12

What is in store for the Interactive Autism Network (IAN)?

The Interactive Autism Network’s Research could be called longitudinal in that we gather information from families over time. For example, during the first five years of our study (2007-2012), parents tracked the treatments that they gave their children. We hope to enhance the information that we collect from families so that we can follow the developments and changes that occur in our participants’ lives through the years. So stay tuned!

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Additional Resources: 

The following articles explore additional longitudinal studies in autism: Long-term Studies Track How Autism Changes with Age and Tony Charman: Longitudinal Studies for Autism research.

To learn more about the findings from the Adolescents and Adults with Autism view autism researcher Marsha Mailick’s talk.

  1. History of the Framingham Heart Study. (n.d.). . Retrieved July 3, 2014, from
  2. Research Milestones. (n.d.). . Retrieved July 3, 2014, from
  3. 20th Anniversary of the Nurses’ Health Study II. (2009, January 1). Nurses' Health Study Newsletter, Volume 16, 2009, 16, 1-2.
  4. Lyall, K., Constantino, J.N., Weisskopf, M.G., Roberts, A.L., Ascherio, A., Santangelo, S.L. (2014), Parental social responsiveness and tisk of autism spectrum disorder in offspring. JAMA Psychiatry. Published online June 18, 2014. doi:10.1001/jamapsychiatry.2014.476.
  5. Adolescents and adults with autism: A study of family caregiving. (2014, January 14). Retrieved July 3, 2014, from
  6. Supporting Adolescents and Adults with Autism: Critical Life Transitions. (2014, May 17). Retrieved July 3, 2014, from
  7. Taylor, Julie Lounds. Email interview by Cheryl Cohen (2014, March 24).
  8. Autism Speaks Baby Siblings Research Consortium: 2012 Annual Report. (2013). Retrieved July 25, 2014, from
  9. Zwaigenbaum, L., Bryson, S.E., Szatmari, P., Brian, J., Smith, I.M., Roberts, W., Vaillancourt, T., Roncadin, C. (2012). Sex differences in children with autism spectrum disorder identified within a high-risk infant cohort. Journal of Autism and Developmental Disorders, 42, 2585-96.
  10. Landa, R.J., Gross, A.L., Stuart, E.A., & Bauman, M. (2012). Latent class analysis of early developmental trajectory in baby siblings of children with autism. Journal of Child Psychology and Psychiatry, 59, 986-996.
  11. Landa, R., Garrett-Mayer, E. (2006). Development in infants with autism spectrum disorders: a prospective study. Journal of Child Psychology and Psychiatry, 47, 629-638.
  12. Newschaffer, C.J., Croen, L.A., Fallin, M.D., Hertz-Picciotto, I., Nguyen, D.V., Lee, N.L., Berry, C.A., Farzadegan, H., Hess, H.N., Landa, R.J., Levy, S.E., Massolo, M.L., Meyerer, S.C., Mohammed, S.M., Oliver, M.C., Ozonoff, S., Pandey, J., Schroeder, A., Shedd-Wise, K.M. (2012). Infant siblings and the investigation of autism risk factors. Journal of Neurodevelopmental Disorders. 4:7.