Description of the condition
Children with developmental co-ordination disorder (DCD) (APA 2013) have significant difficulty in performing the essential motor tasks required for self care (for example, dressing), social and recreational activities (for example, riding a bicycle), and academic achievement (for example, handwriting) as compared with typically developing children of the same age. Additionally, the disturbance in movement skills is not explained by any known medical conditions (APA 2013).
A diagnosis of DCD is made if the child satisfies the diagnostic criteria from the Diagnostic and Statistical Manual for Psychiatric Disorders 5 (DSM-5) (APA 2013). The assessment involves taking a developmental history, performing a clinical examination to rule out possible medical conditions, assessing the child's functional motor skills (usually through parent or teacher report), and objectively assessing the child's motor competence using a performance-based motor assessment (Blank 2012). DCD is usually diagnosed between the ages of five and 16 years (Blank 2012). By definition, children with suspected DCD should be free from definite neurological conditions (Gibbs 2007); however, minor neurological dysfunctions are frequently reported in children with DCD, suggesting that early brain lesions might be causative (Hadders-Algra 2003). Moreover, studies on imaging report differences in neural networks and brain activation patterns between children with DCD and control children (Kashiwagi 2009; Zwicker 2010).
The prevalence of DCD has been cited as 6% of school-aged children (APA 2013) and the male to female ratio has been reported as 1.9 to 1 in a recent UK study of seven-year-olds (Lingam 2009). DCD may also be referred to as clumsy child syndrome, dyspraxia (Miyahara 2000), or specific developmental disorder of motor function (World Health Organization 2010). Currently, the DSM-5 criteria accept comorbidities of DCD with attention-deficit and/or hyperactivity disorder, communication disorders, intellectual disability, and specific learning disorders (APA 2013).
DCD is included in the manual of mental disorders because of its consequential avoidance behaviours and psychosocial impacts (Spitzer 1994). The self esteem of children with DCD, in terms of physical competence, is diminished to a greater extent than that of children with severe physical disabilities (Miyahara 2006). They are likely to be onlookers in playgrounds, isolated and solitary in the school yard (Smyth 2000). Rejection by their peers can lead to children with DCD missing out on important socialisation experiences, resulting in suboptimal social skills (Cummins 2005). They may be easy targets for bullies (Piek 2005). Their levels of depressive symptomatology and anxiety are higher than typically developing children (Schoemaker 1994) and adolescents (Cantell 1994). DCD influences children's physical functions and health status, as well as their emotional life and social participation, not only during childhood but also throughout adolescence (Losse 1991) and adulthood (Cousins 2003; Missiuna 2008). Their reduced levels of participation in physical activity (Cairney 2005) have secondary consequences, such as reduced cardio-respiratory fitness (Cairney 2006), and increased risk for obesity and coronary vascular disease (Cairney 2007). While the motor difficulties of children with DCD may appear to be less debilitating than those experienced by children with severe physical disabilities (for example, cerebral palsy), it is the high prevalence of DCD, and its impact on children's socio-emotional well-being and future health status, that makes DCD a significant condition in need of appropriate intervention.
DCD is often measured using performance-based and impairment-based motor outcomes. Performance-based outcomes assess general motor ability, which underpins activities of daily living and academic performance. These measures employ neutral tasks which vary slightly from real-life functional tasks to avoid item bias. They are also standardised, objective, and sensitive to change. Some measures of task performance, such as the Canadian Occupational Performance Measure (COPM) or the Goal Attainment Scale (GAS), offer a self report perspective of task-related outcomes and are used to complement objective measures of task performance. Impairment-based measures, an historic way of approaching intervention and assessment, cover the spectrum of WHO categories (Impairment, activity limitations, participation restrictions).
Description of the intervention
Existing interventions range from movement-based therapies and education (usually provided by physiotherapists, occupational therapists, and physical educators) to pharmacology, dietary supplements, and counselling. Traditionally, the movement-based approaches have been classified in accordance with the emphasis of the intervention; that is, task-oriented or process-oriented. Interventions that focus on the performance of specific movement tasks or 'occupations', such as tying shoelaces, ball catching, and handwriting, are collectively called task-oriented approaches. Within the task-oriented approach are task-specific training (Revie 1993), cognitive motor approach (Henderson 1992), cognitive orientation to daily occupational performance (CO-OP) (Missiuna 2001), neuromotor task training (NTT) (Schoemaker 2003), and ecological intervention (Sugden 2007). The common theme of the task-oriented approaches resides in the employment of specific tasks in an attempt to improve corresponding skills. The differences between the task-oriented approaches depend on where the relative emphasis is placed, such as task-specificity in motor skill learning (Revie 1993), the interaction between cognitive, affective, and motor competence (Henderson 2007), child-centred cognitive strategies (Missiuna 2001), analysis of neuromotor processes underlying motor control (Schoemaker 2003), and making the task relevant and ecologically valid (Sugden 2007). In contrast, process-oriented approaches work on the principle that there is an underlying deficit, which must be remediated before functional change can take place. One of the most popular approaches in this category is sensory integration therapy, first devised by Ayres in the 1960s, which aims to improve the effectiveness and efficiency of processing and coordinating sensory information input in order to improve motor performance (Ayres 1979). However, there is more evidence against the effectiveness of this approach than in favour of it (Zimmer 2012). In this review, we will evaluate existing research on the more recently proposed task-oriented approaches in comparison to these other process approaches so that consumers and professionals have the opportunity to make informed decisions.
How the intervention might work
Based on principles of motor control and learning, task-oriented approaches involve concentration on the tasks, or group of tasks, to be mastered. In essence, they capitalise on the assumption that learning and skill acquisition is strongest when the learner understands the meaning of the training, and finds the task to be useful or relevant to his or her life. Thus, aspects of motivation and engagement are catered for, as well as the current understanding around brain plasticity, which supports the idea that learning effectiveness is enhanced when the individual perceives the goal, or likely reward, as functional and beneficial (Hoerzer 2012). At the behavioural level, the intervention effects are explained in terms of the variables involved in motor learning, such as repetition, duration, intensity, frequency of practice, and the types of feedback given (Keogh 1985; Henderson 1992; Revie 1993; Schoemaker 2003). At the cognitive level, the improvement of motor skills is explained in terms of intellectual understanding of motor tasks and verbal mediation, or talking through movements in the process of perceiving stimuli, and preparing and executing movements (Cratty 1989; Henderson 1992; Missiuna 2001). The impact of incorporating ecological aspects involves adapting or manipulating the environment and context to reproduce, as closely as possible, the actual learning task environment. This ensures contextual relevance and meaning, and thus is ecologically valid to the child with the support of significant others such as parents and teachers (Sugden 2007).
Why it is important to do this review
Parents of children with DCD need a readily understandable review to help them make informed decisions about the best available interventions, as do service providers. Since the publication of the recent systematic (Hillier 2007) and meta-analytic reviews (Pless 2000) of the intervention effects for children with DCD, new evidence has accumulated. The latest systematic and meta-analytic reviews (Smits-Engelsman 2013; Wilson 2013) include the recent evidence only, and do not evaluate these data together with older evidence. The meta-analytic studies also considered the intervention effects of the foregoing studies altogether, rather than examining the differential intervention effects of the children's age, the environment of intervention, and interventionist (Hillier 2007). The identification of differential intervention effects would allow service providers and consumers to make more informed decisions. It is of clinical and theoretical interest whether the intervention effects are transferred from the specific intervened tasks to general motor ability.