How common are motor problems in children with a developmental disorder: rule or exception?

BACKGROUND Few co-morbidity studies have been conducted since the Leeds Consensus Statement on developmental co-ordination disorder (DCD) in 2006. In this Statement, international cut-offs and inclusion criteria were agreed and consequently, the status of DCD changed. Furthermore, most existing co-morbidity studies are small clinical studies, rather than epidemiological studies, resulting in a broad range of co-morbidity rates. DCD has a higher incidence for boys in comparison with girls; questions arise if this preponderance remains the same in combination with other developmental disorders. Therefore, in this study we aimed to determine co-morbidity and gender differences of motor problems in children with a pervasive developmental disorder, a hyperkinetic disorder and/or a speech, language or learning disability. METHODS Profiles of 3608 children (mean age: 9 years 1 month) referred to rehabilitation centres for behavioural, developmental and sensorineural disorders were studied. RESULTS Motor problems were reported in one-fifth of the total sample. Co-morbidity of motor problems in specific disorders varied from almost one-fourth to more than one-third. The male/female ratio was significantly higher in children with motor problems and two or more other disorders, compared with children with motor problems and less than two other disorders. CONCLUSIONS This study indicates that co-morbidity of motor problems with other clinical disorders is not exceptional and developmental deviance is seldom specific to one domain. However, current co-morbidity studies tend to overestimate the number of children with motor problems. In addition, there may be different patterns of symptoms between the genders. These findings stress the importance of assessing motor skills in children with various developmental disorders.