Challenges and opportunities in using mixed method designs in rehabilitation research.

Rehabilitation research is faced with complex challenges. Heterogeneous patient populations in terms of clinical presentations, scope of functional impairment, comorbidity, and sociodemographics (eg, age, education) make powerful, blind, randomized controlled trials difficult. Even large treatment centers are often unable to provide sample sizes that would allow meaningful comparisons with controls. The problems with the feasibility of conducting randomized controlled trials are compounded by criticism directed at intervention research in terms of low external validity, and clinical and practical relevance for individual patients living in the community. This article introduces mixed method designs and discusses their relevance in the context of rehabilitation research. Examples are provided from diverse clinical research areas such as spinal cord injury and mixed disability populations.