Development and validation of the 48-item Symptom Questionnaire (SQ-48) in patients with depressive, anxiety and somatoform disorders.

Self-report measures of psychological distress or psychopathology are widely used and can be easily implemented as psychiatric screening tools. Positive psychological constructs such as vitality/optimism and work functioning have scarcely been incorporated. We aimed to develop and validate a psychological distress instrument, including measures of vitality and work functioning. A patient sample with suspected depressive, anxiety, and somatoform disorders (N=242) and a reference sample of the general population (N=516) filled in the 48-item Symptom Questionnaire (SQ-48) plus a battery of observer-rated and self-report scales (MINI Plus, MADR, BAS, INH, BSI), using a web-based ROM programme. The resulting SQ-48 is multidimensional and includes the following nine subscales: Depression (MOOD, six items), Anxiety (ANXI, six items), Somatization (SOMA, seven items), Agoraphobia (AGOR, four items), Aggression (AGGR, four items), Cognitive problems (COGN, five items), Social Phobia (SOPH, five items), Work functioning (WORK, five items), and Vitality (VITA, six items). The results showed good internal consistency as well as good convergent and divergent validity. The SQ-48 is meant to be available in the public domain for Routine Outcome Monitoring (ROM) and can be used as a screening/ monitoring tool in clinical settings (psychiatric and non-psychiatric), as a benchmark tool, or for research purposes.