Cognitive Strengths and Weaknesses Observed in People With 3q29 Deletion Syndrome

3q29 deletion syndrome (3q29Del) is generally associated with mild to moderate intellectual disability. Identifying an Intellectual and Developmental Disability (IDD) is important for helping children and adults get the resources they need. 

By some estimates, 92% of those with 3q29Del display signs of IDD. This figure, however, doesn’t help us to understand the areas of strengths and weaknesses (also called a “cognitive profile”) among the 3q29Del population, or what other factors might contribute to apparent deficits. 

Researchers with the 3q29 Project wanted to describe a more specific cognitive profile of people with 3q29Del. Using modern assessment techniques, they developed a study that looked at a variety of developmental areas (like cognitive, social, and adaptive) within the contexts these occurred (family, community, etc.). 

You can read the full study here or continue reading the overview below.

About the Study

The 3q29 Project recruited 32 volunteers with 3q29Del between the ages of 4-39 (20 males/12 females) to participate in person at Emory University in Atlanta, GA.

This study had two goals:

  1. To gain a better understanding of the cognitive impact of 3q29Del

  2. To determine if the degree of cognitive impact had anything to do with the occurrence of other neurodevelopmental and/or psychiatric conditions

Participants were evaluated on three measures—cognitive ability, adaptive ability, and whether or not they qualified for a neurodevelopmental or psychiatric diagnosis. 

Cognitive Ability Tests

In this study, cognitive ability was measured by how the participants performed on a series of tests that assessed verbal, nonverbal, and spatial skills. The type of test given depended on the person’s age. 

These tests generate subsets of scores called:

  • Verbal IQ (VIQ) – an estimate of verbal skills

  • Nonverbal IQ (NVIQ) – an estimate of nonverbal and spatial skills

  • Full Scale IQ (FSIQ) – a score that estimates overall cognitive functioning and is what we commonly refer to as “IQ”. FSIQ is a combination of the VIQ and NVIQ scores. 

Adaptive Ability Tests

This set of tests predicts the ability to perform the “real life” skills people need to function independently like taking care of their hygiene, managing money, and making friends. Here, information was gathered across three areas:

  • Socialization

  • Daily living skills

  • Communication skills

For this, parents or caregivers filled out a questionnaire electronically. 

Neurodevelopmental and/or Psychiatric Evaluation

Expert clinicians evaluated participants for conditions including anxiety disorder, ADHD, autism spectrum disorder (ASD), depression, and schizophrenia. 

What the Study Found

Cognitive Profile

When the scores of the cognitive and adaptive portions of the test were combined for all participants, the FSIQ of the group as a whole fell into the low-to-normal range. The scores broke down as follows:

Mean FSIQ – 73 (range 40-99)

Mean VIQ – 80 (range 31-106)

Mean NVIQ – 75 (range 53-98)

Mean spatial ability score – 71 (range 34-108)

Mean score for adaptive skills – 74 (range 48-110)

There were some other notable observations:

  • For many 3q29 del study subjects, there were big differences in the VIQ and NVIQ scores. This means that some people with 3q29del can have excellent verbal ability, but have compromised nonverbal reasoning. The opposite can also be true: someone with 3q29 del can have challenges expressing themselves verbally but have strong nonverbal reasoning skills. Females’ FSIQ and VIQ scores were 9 and 10 points higher than males’ on average, respectively. This was a small study so the researchers don’t want to make any conclusions yet about how the scores relate to biological gender. 

  • Age was not significantly associated with FSIQ, VIQ, or NVIQ scores. 

  • The age someone began speaking single words didn’t seem to be associated with VIQ. However, verbal ability was associated with the age at which someone began using  2-word phrases. 

Again, these results reflect the average scores of all 32 participants. However, scores from one person to the next varied quite a bit. This was especially noticeable when it came to verbal skills. 

For example, the average VIQ score was 80 (low-normal) but individual scores ranged from 31 (very low) to 106 (average-high). In other words, some people with 3q29Del may have verbal skills well below those of the general population while others function well in that area.

Of the individuals studied here, 34% (11 participants) met the diagnostic criteria for intellectual disability (ID). For comparison, this number is around 1% among the general population. Those with VIQ lower than NVIQ were more likely to meet these criteria.

Relationship Between Cognitive Profile and Other Diagnoses

In addition to describing the cognitive profile among those with 3q29Del, researchers wanted to understand if there was a relationship between cognitive ability and other neurodevelopmental or psychiatric conditions.

Here’s what they observed in this study:

  • Having a high or low FSIQ did not provide any information about whether someone would also have an additional diagnosis like anxiety disorder, ADHD, ASD, or schizophrenia ASD was associated with lower NVIQ scores.

  • Anxiety disorders were associated with higher NVIQ scores.

  • Cognitive ability was not a good predictor of whether or not someone would be diagnosed with a co-occurring disorder.

What It Means

This study suggests that many factors need to be taken into account when characterizing the relative strengths and weaknesses of skills associated with 3q29Del. It’s a complex combination of cognitive and adaptive abilities, language development, and co-occurring conditions. 

When all of the participants’ scores were put together, they fell within a range of what would indicate mild intellectual disability. However, some displayed moderate disability while others had cognitive and adaptive skills within a normal range. 

It’s also possible that the relative verbal strength demonstrated with 3q29Del could mask underlying areas of relative weakness. This may explain why despite the fact that only 34% of study participants met the criteria for IDD, a much higher percentage of children with 3q29Del receive special education services “in real life”. In other words, even though assessments might suggest kids with 3q29Del function at an average level, there are often areas where they require additional academic support. 

Finally, since cognitive ability did not predict risk of co-occurring developmental or psychiatric conditions, the researchers emphasize the importance of behavioral evaluations for everyone with 3q29Del.

This study was limited by the small sample size. It may also inaccurately represent the 3q29Del population because only those who were willing and able to travel to Atlanta were evaluated in this case.