Autism is diagnosed about 5 times more frequently in boys than in girls. The presentation of autistic traits in girls is often very different than in boys. However, most autism research in the past has been focused only on boys. As a result, we don't yet fully understand the relationship between biological sex and autism.

The goal of the Girls with Autism Imaging of Neurodevelopment (GAIN) Study is to better understand sex differences in autism. Eventually, we hope this information will help us in finding the best ways to identify and support autistic girls.


The GAIN Study started in 2014, led by Dr. Christine Wu Nordahl. Both autistic and non-autistic girls were enrolled in the study when they were between 2-4 years old. We then followed up with them at time points one year and two years later. We look at many different factors to help us get a complete picture of each child. This includes behavioral and neuropsychological assessment, medical history, blood draw, and an MRI scan of the brain.

Over 120 girls have participated in our research program to date. The GAIN Study is the largest MRI study of young, autistic girls in the world. We are very appreciative to all of the families that have participated so far and have helped us to improve our understanding of autism.

Current and related studies

Current phases of GAIN

We are continuing to follow-up with the original participating families, as well as enroll new participants.

Early Childhood

In the early childhood phase of the study, we hope to improve our understanding of early brain development, behavioral presentations of autism, and co-occurring medical conditions in young girls. Depending on their child's age at enrollment, families may be asked to return for follow-up visits 1 year and 2 years after they first join the study.

We are currently enrolling autistic and non-autistic girls who are 2-6 years old.

Middle Childhood

Autism can impact individuals differently throughout life. In this phase of the GAIN, we focus on autistic traits, co-occurring medical and mental health conditions, and brain development. We are particularly interested in emergence of ADHD and anxiety. We also are looking at how behavioral or biological characteristics in early childhood may predict the strengths and challenges a child will face in middle childhood.

We are currently inviting families who participated in previous phases of GAIN to return for this phase of the study when their child is 9-12 years old.

We are also enrolling autistic and non-autistic boys and girls who are 11-12 years old in our related study, APP.

If you are interested in participating in any of the studies listed above, please contact our team
at hs-GAINStudy@ucdavis.edu.

Related studies

The GAIN Study builds on the work of the Autism Phenome Project (APP), a long-running study at the MIND Institute. We work closely with the APP and other related studies: