My breakdown of the autism Princeton study... part 4

I think I'm finally ready to get into the biological / genetic findings of the study. 

But first, for context, so you understand the lens I am looking through and why my content can be trusted...

I'm not a scientist or biologist... but I do have a psychology degree, which included training in statistics and research methods. 

So though biology is not my area of expertise, I do have formal training in reading and analyzing research. 

And my actual expertise, as in, what I do for a living, is in making extremely complex information understandable and digestible... 

So, with that said... let's get into it.

As a reminder, the study identified 4 distinct groups within the autistic sample group. 

Many have been calling these groups "subtypes." 

If you didn't see my part 1 of this series where I explain why the term "subtype" is causing confusion, you may want to go back and look for it. But in this post, I'll be referring to them as groups.

So, the four groups identified were...

1. The Social Behavioral group, which had somewhat noticeable social and behavioral autistic traits, no developmental delays, and commonly presented with ADHD and other co-occurring psychiatric conditions.

2. The Moderate Challenges group, which also did not have developmental delays, had the least noticeable autistic traits of all the groups, and did not have co-occurring psychiatric conditions.

3. The Mixed ASD with Developmental Delays group, which had developmental delays, as the name suggests, and more noticeable autistic traits than the previous two groups, but no co-occurring conditions.

4. And the Broadly Affected group, which had developmental delays, the most noticeable traits and challenges of all the groups, and co-occurring psychiatric conditions including depression, anxiety, and mood dysregulation. 

In addition to everything I just mentioned, the study also uncovered patterns related to biology and genetics...

Here are some key features the researchers looked at to identify biological and genetic patterns within the 4 groups...

- They looked for genetic mutations (so genetic markers that don't typically show up in nonautistic individuals) and when the affected genes became active... whether prenatal, or postnatal / in early childhood development.

- And they looked at whether or not the mutations were found in the parents of the autistic participants. In other words, if they were inherited.

Ok, so now I'm going to explain how the biological and genetic patterns showed up within each group.

1. I'll start with the Broadly Affected group because I'm seeing a lot of people misinterpret this part of the research and I think the details and nuances are important...

In the broadly affected group the study found that the gene changes happened before birth and occurred in parts of the brain that are really important for early development. Some of the affected genes were also part of a group that has been linked to Fragile X syndrome.

These kinds of gene mutations were considered "de novo," meaning they were not found in the parents of the autistic participants. In other words, they were new mutations that happened spontaneously in the child.

But this is the part I want to clarify because I see a lot of people misunderstanding what this means. 

This finding does NOT automatically mean that their autism wasn't inherited or that the parents can't be autistic. It just means that they didn't have the same specific gene mutations found in their child.

It's possible for one or both of the parents to also be autistic, but to have traits linked to a different type of genetic pattern associated with other autistic presentations.

But I think it's extremely important to understand that a child presenting with very noticeable autistic traits and very high support needs CAN have an autistic parent or parents with lower support needs and mostly hidden traits. This study does not rule that out as a possibility.

2. Next, let's dig into the biological and genetic patterns found in the Mixed ASD with Developmental Delays group...

In this group, the gene changes also happened before birth (referred to as prenatal expression) just like the Broadly Affected group.

So the affected genes were active during early brain development, which is likely why these children had developmental delays. 

But biologically, this group stood out from the others because the gene mutations were both inherited AND de novo.

In other words, some of the gene changes were passed down from parents, while others were spontaneous and weren’t found in either parent. 

This pattern is one of the things that differentiated this group from the Broadly Affected group, which had mostly de novo mutations.

Another important finding was that this group didn't show the same psychiatric overlap that was found in the Broadly Affected group. So, no links to behavioral conditions like ADHD or depression.

3. Okay, now let's dig into the biological and genetic patterns found in the Social / Behavioral Challenges group...

For this group, the study found that the affected genes became active after birth... in early childhood rather than during pregnancy. This is called postnatal expression.

Now, an important point I want to clarify, because I've seen this misstated a lot. 

Postnatal in the context of this study does NOT indicate that the genes became active later in LIFE. As in, in adulthood. 

We are talking specifically about later in childhood, because the study only included participants up to the age of 18. So nothing in the postnatal findings refers to traits that showed up in adulthood.

Ok, back to what they found for the Social / Behavioral group...

In this group, the genes were especially active in areas of the brain that impact behavior regulation. These are areas that tend to become more important as children grow and enter more structured social environments, like school.

Unlike the Broadly Affected group, most of the genetic mutations in this group were inherited. In other words, the parents had many of the same gene differences as their children. 

But these weren’t high-impact, rare mutations like those found in the first group. They were more common inherited variants, especially ones that are also associated with ADHD, anxiety, and depression.

4. OKAY last but definitely not least... let’s dig into the biological and genetic patterns found in the Moderate Challenges group…

For context, I suspect a lot of higher masking, lower support needs autistic people will see themselves in this group. I personally think I most likely would match the patterns found here if my genes were analyzed. That said...

In this group, the affected genes became active before birth, so prenatally, BUT...

Unlike the other two groups with prenatal expression, the changes in this group occurred in genes that are not heavily involved in early development, which could explain why this group didn’t show noticeable developmental delays.

There WERE some de novo genetic mutations in this group, but they weren't concentrated in high-impact genes like in the Broadly Affected group. So the genetic profile for this group looked milder overall.

Another important finding for this group, was that it didn’t show the psychiatric overlap found in the Broadly Affected or Social / Behavioral groups. So, no links to ADHD, anxiety, or mood-related conditions.

Whew. Ok, I know that was a lot. And I'm sorry this post had to be so long 😅 but there's a ton of complexity and nuance here, and I really didn't want to oversimplify it and lose important details. 

I still have a lot more to share about this study. Especially when it comes to my own understanding of my autism, which I think will resonate with a lot of you. So if you're interested in that, stick around for part 5.

In the meantime, let me know what you think of all of this!