Can a Questionnaire Help Distinguish DCD from ADHD in Adults?

What you need to know

• The Adult Developmental Co-ordination Disorders/Dyspraxia Checklist (ADC) was translated into German and tested in adults with DCD and/or ADHD.
• A restructured version with subscales for gross motor, fine motor, and executive function skills shows promise for distinguishing DCD from ADHD.
• The revised questionnaire may help identify unique symptom profiles in adults with DCD versus ADHD.

Background on DCD and the ADC

Developmental Coordination Disorder (DCD) is a condition that affects motor skills and coordination. While it’s often diagnosed in childhood, DCD can persist into adulthood and impact daily life. However, there are few tools available to screen for or assess DCD in adults.

The Adult Developmental Co-ordination Disorders/Dyspraxia Checklist (ADC) is one of the few existing questionnaires to screen adults for potential DCD. It was originally developed in English and Hebrew. The ADC asks about coordination difficulties in childhood and current symptoms in adulthood.

However, the ADC may not distinguish well between DCD and other conditions with overlapping symptoms, like attention-deficit/hyperactivity disorder (ADHD). This study aimed to create a German version of the ADC and explore how it might be improved to better differentiate DCD from ADHD.

Translating and Testing the German ADC

The researchers first translated the ADC from English to German using a structured process. They then tested this German version in a small pilot study with 19 participants - 8 with DCD or self-reported severe coordination difficulties, and 11 matched controls.

This initial testing showed the German translation worked well overall. People with DCD scored significantly higher than controls on the total ADC score and all subscales. However, the researchers identified some ways the questionnaire could be improved based on participant feedback.

Revising and Restructuring the ADC

In the next phase, the researchers made some revisions to the German ADC based on the pilot feedback. They added examples and clarifications to some items that participants found confusing. They also added a “does not apply” option for certain questions, like those about driving, to account for people who may avoid activities due to coordination difficulties.

The revised German ADC was then tested in a larger online study with 148 participants who had a diagnosis of DCD and/or ADHD. The researchers used this larger dataset to take a fresh look at how the questionnaire items clustered together.

Through statistical analysis, they identified three main groupings of items:

1. Gross motor skills
2. Fine motor skills
3. Executive functions

This was different from the original ADC structure, which had sections on childhood symptoms, current symptoms, and symptoms noticed by others.

How the New Structure Compares

The researchers compared how well the original ADC structure versus this new three-factor structure could distinguish between participants with DCD, ADHD, or neither condition.

They found the new structure showed more promise for differentiating DCD from ADHD. Specifically:

• People with DCD tended to report more difficulty with gross motor skills
• People with ADHD tended to report more difficulty with executive functions
• Both groups reported similar levels of fine motor difficulties

This aligns with what we know about the core symptoms of each condition - DCD primarily affects motor skills, while ADHD primarily affects attention, impulse control, and other executive functions.

Importantly, the executive function subscale scores were similar between DCD and ADHD groups. This supports other research showing executive function difficulties are common in DCD, even without co-occurring ADHD.

Testing in English Speakers

To see if these findings would hold up in other languages, the researchers applied the new three-factor structure to existing ADC data from 134 English-speaking adults.

The results were similar to the German sample. The gross motor, fine motor, and executive function subscales showed good reliability. And again, the DCD group scored higher on gross motor items while the ADHD group scored higher on executive function items.

This suggests the new structure could be useful across languages for identifying different symptom profiles in DCD versus ADHD.

Potential Benefits of the Restructured ADC

The revised ADC structure with gross motor, fine motor, and executive function subscales shows several potential advantages:

• It may help distinguish between adults with DCD versus those with ADHD more effectively than the original ADC structure.

• It provides more detailed information about a person’s specific areas of difficulty (e.g. gross motor versus fine motor skills).

• It highlights that executive function difficulties can occur in DCD even without ADHD, which clinicians should be aware of.

• The symptom-based structure may be more intuitive and meaningful than the original temporal structure (childhood versus current symptoms).

Limitations and Future Directions

There are some important limitations to keep in mind:

• The sample sizes were relatively small, especially for adults with confirmed DCD diagnoses. Larger studies are needed to confirm these findings.

• Diagnoses were self-reported and not independently verified by the researchers.

• The restructured ADC has only been tested to distinguish DCD from ADHD so far. Its ability to differentiate DCD from other conditions still needs to be examined.

• While promising, the restructured ADC is not meant to be used alone for diagnosis. A comprehensive assessment by a qualified clinician is still necessary to diagnose DCD or ADHD.

Future research should:

• Test the revised ADC structure in larger samples
• Examine how well it distinguishes DCD from other neurodevelopmental and motor disorders
• Explore whether different cutoff scores may be needed for the new subscales
• Investigate whether the restructured ADC could be useful for assessing treatment progress over time

Conclusions

• The German translation of the ADC shows good reliability and validity for assessing DCD symptoms in German-speaking adults.

• Restructuring the ADC into gross motor, fine motor, and executive function subscales may help differentiate between adults with DCD versus ADHD.

• The revised structure highlights that both motor and executive function difficulties are common in DCD, even without co-occurring ADHD.

• While promising, more research is needed before the restructured ADC can be widely implemented in clinical practice.

• The ADC should be used as a screening tool to complement, not replace, comprehensive clinical assessment for diagnosing DCD or ADHD in adults.

This study takes important steps toward improving how we assess and distinguish DCD from other conditions in adulthood. With further development, tools like the restructured ADC may help clinicians better recognize DCD in adults and tailor interventions to each individual’s specific areas of difficulty.