BACKGROUND: Our objective was to investigate to what extent the Clinical Interview for Depression (CID) used in the general practice setting covers clinically valid subscales (depression, anxiety, and apathy) which can measure outcome of antidepressant therapy as well as identifying subsyndromes within major depressive disorder. The CID was compared to the Hamilton Depression Rating Scale (HAM-D17).

METHODS: 146 patients from a previous study in general practice with the CID were investigated. The item response theory model established by Rasch was used to investigate the scalability (a scale׳s psychometric adequacy) of the subscales, and principal component analysis was used to identify subsyndromes with the symptoms of major depression according to DSM-5 or ICD-10.

RESULTS: Whereas the HAM-D17 was found not to have an acceptable scalability, the three brief CID subscales for depression (six items), anxiety (five items), and apathy (five items) all had an acceptable scalability. Within the major depressive symptoms, principal component analysis identified the CID items of hypersomnia, increased appetite or weight gain as defining the subsyndrome of atypical depression. In total 29 patients (approximately 20%) had an atypical depression.

LIMITATIONS: The samples were derived from a single study and were all rated by a single rater.

CONCLUSION: The CID contains subscales of depression, anxiety, and apathy with an acceptable scalability for use in general practice. A subsyndrome of atypical depression is also a useful identifier in the treatment of depressed patients in general practice.