Development and validation of the Intrinsic Religiousness Inventory (IRI)

objective: the role of religious involvement in mental health has been increasingly investigated in psychiatric research; however, there is a shortage of scales on religiousness in portuguese. the present study aimed to develop and validate a brief instrument to assess intrinsic religiosity (intrinsic religiousness inventory - iri) in two brazilian samples. method: the initial version was based on literature review and experts' suggestions. university students (sample 1; n = 323) and psychiatric patients (sample 2; n = 102) completed the duke religiosity index (durel), the iri, an instrument of spirituality measurement (whoqol-srpb), as well as measurements of anxiety and depressive symptoms. results: the iri showed adequate internal consistence reliability in sample 1 (cronbach's α = 0.96; 95% ci; 0.95-0.97) and sample 2 (α = 0.96; 95% ci; 0.95-0.97). the iri main component analyses indicated a single factor, which explained 73.7% and 74.9% of variance in samples 1 and 2, respectively. strong correlations between iri and intrinsic subscale of the durel were observed (spearman's r ranging from 0.87 to 0.73 in samples 1 and 2, respectively, p < 0.001). the iri showed good test-retest reliability (intraclass correlation coefficients > 0.70). conclusion: these data indicate that the iri is a valid instrument and may contribute to study intrinsic religiosity in brazilian samples.