Validity of the 15-item social inhibition questionnaire in outpatients receiving psychological or psychiatric treatment: The association between social inhibition and affective symptoms

Objective
Social inhibition may promote symptoms of depression and anxiety in adults from an outpatient hospital population. The current work builds on a previously corroborated construct of social inhibition and examines the psychometric properties of this assessment tool and its predictive validity in the adult outpatient hospital population.

Methods
A total of 350 adult outpatients receiving treatment at the department of Medical Psychology or Psychiatry completed measures of social inhibition and symptoms of anxiety (7-item Generalized Anxiety Disorder scale) and depression (9-item Patient Health Questionnaire). Factor analyses, reliability estimates, and regression analyses were used to replicate the robustness of the model of social inhibition, and the 15-item Social Inhibition Questionnaire (SIQ15).

Results
In the current sample (N =350; Mage =45 years; 67.4% women), factor analyses confirmed the previously suggested three-factor model of social inhibition as measured by the SIQ15. The subscales of behavioral inhibition, interpersonal sensitivity and social withdrawal proved to be internally consistent (Cronbach's α be-tween 0.87/0.95) and stable over time (test-retest reliability between r =0.76/0.83). At baseline, interpersonal sensitivity and social withdrawal were associated with anxiety and depressive symptoms. At three months follow-up, only interpersonal sensitivity was related to depressive symptoms.

Conclusions
Social inhibition is associated with anxiety and depression at baseline and can be reliably assessed with the SIQ15 in an outpatient hospital population. The association of interpersonal sensitivity with depressive symptoms at three-month follow-up suggests an important aim for future research on the development of preventive methods for affective symptoms in socially inhibited outpatients.