Selective Mutism Questionnaire: measurement structure and validity.

OBJECTIVE: To evaluate the factor structure, reliability, and validity of the 17-item Selective Mutism Questionnaire (SMQ).

METHOD: Diagnostic interviews were administered via telephone to 102 parents of children identified with selective mutism (SM) and 43 parents of children without SM from varying U.S. geographic regions. Children were between the ages of 3 and 11 inclusive and comprised 58% girls and 42% boys. SM diagnoses were determined using the Anxiety Disorders Interview Schedule for Children-Parent Version; SM severity was assessed using the 17-item SMQ; and behavioral and affective symptoms were assessed using the Child Behavior Checklist. An exploratory factor analysis was conducted to investigate the dimensionality of the SMQ and a modified parallel analysis procedure was used to confirm exploratory factor analysis results. Internal consistency, construct validity, and incremental validity were also examined.

RESULTS: The exploratory factor analysis yielded a 13-item solution consisting of three factors: social situations outside of school, school situations, and home and family situations. Internal consistency of SMQ factors and total scale ranged from moderate to high. Convergent and incremental validity was also well supported.

CONCLUSIONS: Measure structure findings are consistent with the three-factor solution found in a previous psychometric evaluation of the SMQ. Results also suggest that the SMQ provides useful and unique information in the prediction of SM phenomena beyond other child anxiety measures.