Related Disorders

Do some children with DCD have other developmental disorders?

When DCD is present, there is an increased likelihood of other co-occurring conditions, such as attention deficit hyperactivity disorder (ADHD), learning disabilities (LD), specific language impairment (SLI), and behavioural disorders. The two most widely recognized conditions that commonly co-occur with DCD are ADHD and LD. There also seems to be a strong correlation between DCD and SLI. The significant overlap between DCD and these developmental disorders has prompted some researchers to conclude that "pure" DCD may be the exception and not the rule. While there is a demonstrated link between DCD and other developmental conditions, the explanations for their co-occurrence are not yet definitive.

The presence of any co-occurring condition warrants referral to appropriate health care professionals in order to develop an effective and integrated treatment strategy for the child with DCD. It is important to note that unless all co-occurring conditions are identified, there is a strong possibility that the child's motor problems may not be addressed by the educational system. It has been suggested that when more than one set of diagnostic criteria are met (e.g., ADHD and DCD, or language disorders in addition to DCD), more than one diagnosis should be given.

Are there any other associated conditions?

Children with DCD also have a much higher likelihood than other children of having associated social, emotional and behavioural problems. However, debate continues regarding whether some of these conditions are actually co-occurring or secondary to the movement difficulties. It is possible that the presence of emotional difficulties, for example, may occur as a secondary consequence of DCD. It is particularly important to be aware of the potential for these associated conditions, not only when first noticing motor difficulties but also as the child matures, when these issues can become more prominent. As with co-occurring attention and learning problems, involvement of other specialized health care professionals to address issues of associated conditions is critical for the successful management of the child with DCD.

Attention Deficit Hyperactivity Disorder

What is the current evidence about ADHD and DCD?



of children who are diagnosed with ADHD are also diagnosed with DCD

There is a growing body of evidence suggesting that children with attention deficit/hyperactivity disorder (ADHD) have an extremely high rate of co-occurring DCD. Several studies conducted with children with ADHD found that at least 50% of these children also had DCD. Additionally, a few studies have shown that children with the primarily inattentive subtype of ADHD may have the highest rate of motor impairment.

Children who have both ADHD and DCD also have higher rates of problems in selective language functioning, learning abilities and social skills. Outcomes for this group of children appear to be much less favourable than for children with DCD alone and they tend to require more services. Several researchers have suggested that "pure" ADHD is relatively unusual. Based on these findings, all children with attention or learning problems should be assessed for signs of motor impairment.

What might you see?

The overlap between DCD and ADHD can make it difficult to determine whether one or both of these disorders is present. It may appear that children with DCD are not paying attention because they have difficulty keeping their bodies and joints stable, so they look restless. In addition, they may not pay attention well to motor-based tasks that are performed in school, especially if they involve handwriting or other manual skills. When motor problems are present, children may purposely avoid tasks that require motor skills and wander around the classroom, asking to use the bathroom, poking and bothering other children and so on.

The reverse of this problem can also be true. Children with ADHD, particularly the inattentive type, may appear to be clumsy because they do not watch carefully when they cross a room or run across a playground. Children who are hyperactive may bump into other children by accident or have difficulty focusing during ball games. As has been mentioned, at least 50% of children with ADHD also have motor-based problems significant enough to meet the diagnosis of DCD. Careful observation of the types of tasks and settings that are most difficult for the child as well as input from health care professionals can be very helpful in determining which disorders may be present.

Specific Language Impairment

What is the current evidence about Specific Language Impairment (SLI) and DCD?

Similar to studies looking at the overlap between ADHD and DCD, many studies have shown that approximately half to as many as 90% of children with identified speech-language disorders also have co-occurring coordination difficulties. The significant overlap between these two disabilities has led researchers to question the underlying causes of motor and speech-language disorders, which may be common to both conditions.

What might you see?

Unlike the situation with DCD and ADHD, it is usually a little easier to determine whether a child has a motor-based problem, a speech-language-based problem, or both. The type of speech and language difficulties will vary depending upon the severity, type of disorder, and age of the child.

The condition may include difficulties in understanding and/or expressing the following:

  • Semantics - errors in the meaning of words, a limited amount of speech, limited vocabulary, difficulty learning new words, word-finding or vocabulary errors
  • Grammar - errors in sentence structure such as shortened sentences, simple grammar structures, limited grammar, leaving out critical parts of sentences, use of unusual word order
  • Articulation - errors with speech sounds, unclear or slowed speech, repetition of syllables, difficulty with stress in speech

In speech and language disorders, children often have delayed language development, with parents reporting that their child is or was late to talk (e.g., saying his/her first words after 18 months of age, having a vocabulary or less than 50 expressive words and/or not putting words together at 2 years of age). In all speech and language conditions, the difficulties may range from mild to severe. A Speech Language Pathologist can help determine how the communication difficulties affect the child's social and learning needs.

Learning Disabilities

What is the current evidence about LD and DCD?

As with DCD and other co-occurring developmental disorders (attention deficit hyperactivity disorder, and speech language impairment) research indicates that many children with DCD may demonstrate learning difficulties, with poor performance in areas such as reading and reading comprehension, writing, mathematics, and spelling. The co-occurrence of learning difficulties appears to be unrelated to the extent of the motor problem, occurring in cases of both mild and more significant motor impairment.

What might you see?

It can be difficult to determine when children are demonstrating a learning or motor difficulty alone, or when both problems are present. Carefully observing the kinds of academic tasks that children perform poorly can help to determine the underlying reasons for the poor performance. For example, when a child's difficulty is primarily motor-based, they may produce written stories that lack the detail and vocabulary you would expect for their age, but they can tell quite elaborate and well-organized stories. Further observation may indicate that their writing is slow and effortful, and that they tend to write shorter stories when asked for written output, as they are not able to complete the task in a reasonable time. However, children demonstrating learning problems alone may experience difficulties that are unrelated to the motor part of the task.

When children demonstrate learning difficulties, they should also be assessed for signs of motor impairment. Input from a team of health care professionals can help to identify the issues and plan intervention designed to meet all of the needs of the child. When learning difficulties are suspected, assessment by a psychologist can be helpful.