Introduction: Autism spectrum disorder (ASD) is a major disability of childhood which is the basis of many mental pressures on children and their families. Regarding the unfavorable effects of this disorder on the family system, the present research aims to design a family- focused therapy based on the integrated human development approach which is a new approach in the treatment of ASD. In this model, to enhance the abilities of the child, family functioning is set the objective as a general unit, and its effectiveness in combination with Floortime therapy which is the center of therapy of this model is investigated. Materials and Methods: This study uses single-subject design framework where 12 children with autism aged between 3 to 8 years old and their families are examined during 5 months; the research data were collected from three phases. In order to examine the effectiveness of therapy, the researcher-built instruments of (DFFAQ), (FEDQ) and (FEAS) were used. Results: According to the results, the percentage of improvement in developmental family functioning in the mixed family- focused therapy group were above 50 percent, especially in the areas of intimacy, engagement, discipline and also the functional-emotional development of children in the self-regulation, attachment, and mutual interaction levels; thus, the improvement were clinically significant. The effectiveness of treatment in mixed therapy was estimated higher than 0.80. Conclusion: The mixed family-focused therapy which was designed in this study can increase the effectiveness of Floortime therapy and be used as an effective therapy for the treatment of ASD.

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