Study of child language development and disorders in Iran: A systematic review of the literature

Child language development and disorder in Iran has been the focus for research by different professions, the most prominent ones among them being psychologists and speech therapists. Epidemiological studies indicate that between 8% and 12% of children show noticeable signs of language impairment in the preschool years; however, research on child language in Iran is not extensive compared to studies in English speaking countries, which are currently the basis of clinical decision-making in Iran. Consequently, there is no information about the prevalence of child language disorders in Iranian population. This review summarizes Iranian studies on child language development and disorder in the preschool years and aims to systematically find the most studied topics in the field of normal development, the assessment and diagnosis of language impairments as well as exploring the current gaps within the body of literature. Three main Iranian academic websites of indexed articles along with four other nonIranian databases were scrutinized for all relevant articles according to the inclusion criteria: Iranian studies within the field of Persian language development and disorders in preschool children published up to December 2013. They are classified according to the hierarchy of evidence and weighed against the criteria of critical appraisal of study types. As this is a type of nonintervention systematic review, the preferred reporting items for systematic reviews and meta-analyses is modified to be more compatible to the designs of eligible studies, including descriptive studies, test-developing and/or diagnostic studies. Several limitations made the process of searching and retrieving problematic; e.g., lack of unified keywords and incompatibility of Persian typing structure embedded in Iranian search engines. Overall, eligible studies met the criteria up to the third level of the hierarchy of evidence that shows the necessity of conducting studies with higher levels of design and quality.