Calgary Depression Scale for Schizophrenia (CDSS)

Depression is reported to be prevalent in 7–75% of patients with schizophrenia, with an average of 25% (Kim et al., 2006; Müller et al., 2005). During the late 1980’s, depression in schizophrenia generated substantial research attention because of its importance in diagnosis, treatment and long-term outcomes of the disorder. Scales for assessing depression in non-psychotic populations have been criticised for being inappropriate for assessing depression in individuals with schizophrenia.

The Calgary Depression Scale for Schizophrenia (CDSS) is a nine item structured interview scale that was designed in 1990 specifically to assess depression independently of symptoms of psychosis in schizophrenia. Originally an 11 item scale (Donald Addington, Addington, & Schissel, 1990), the CDS was developed from, and validated against, the Hamilton Depression Rating Scale (HDRS), Beck Depression Inventory (BDI), and the Brief Psychiatric Rating Scale (BPRS) using factor analysis, internal consistency, and face validity (Donald Addington, Addington, Maticka-Tyndale, & Joyce, 1992; Donald Addington et al., 1990).

The CDS consists of eight structured questions and a ninth observational item that depends on observation over the course of the interview (Kim et al., 2006). Items were constructed to measure: 1. Depression; 2. Hopelessness; 3. Self deprecation; 4. Guilty ideas; 5. Pathological guilt; 6. Morning depression; 7. Early wakening; 8. Suicidal ideation; and 9. Observed depression.

Items are graded on a 4-point Likert type scale (0, absent; 1, mild; 2, moderate; 3, severe), anchored by descriptors (Donald Addington et al., 1992). Point scores of all nine items are summed to obtain the CDS depression score. A score higher than 6 has an 82% specificity and 85% sensitivity for predicting the presence of a major depressive episode.

Psychometric properties

  • Reliable, valid and specific measure of depression in patients with schizophrenia. Measures depression separately from negative and extrapyramidal symptoms. Low correlation with positive and negative symptoms and no substantial correlation with extrapyramidal symptoms
  • High internal consistency: α = 0.76 – 0.86
  • Good internal and inter-rater reliability:
  • High validity: Ability to predict presence of MDD; 2. Correlation with other depression measures; 3. Confirmatory factor analysis
  • Strong construct validity: Single dimension being measured. Confirmed by correlations with other depression rating scales and prediction of major depressive episode
  • Divergent validity: Absence of correlations with positive negative and extrapyramidal symptoms

Settings

  • Used in clinical populations of patients with depression in schizophrenia (DSM-III-R, DSM-IV)
  • Focused on maximising internal and external validity across inpatients and outpatients
  • Has been translated into 40 languages. Validated in: Arabic, Spanish, German, Chinese, Thai, Brazilian, Greek, French

Strengths

  • Quick to administer
  • Sensitive to change, so can be used at both the acute and residual stages of schizophrenia
  • Superior to the Hamilton Depression Rating Scale (HDRS) and Montgomery-Asberg Scale for differentiating between depression and negative and positive symptoms. All items significantly discriminate between the presence and absence of a major depressive episode
  • Most specific and valid assessment of depression in schizophrenia

Weaknesses

  • Scale is designed for use by an experienced rater. It is not intended for self assessment

 

References

Addington, D., Addington, J., & Maticka-Tyndale, E. (1991). Reliability and validity of a depression scale for schizophrenics. Schizophrenia Research, 4(3), 247. https://doi.org/10.1016/0920-9964(91)90089-A

Addington, D., Addington, J., & Maticka-Tyndale, E. (1994). Specificity of the Calgary Depression Scale for schizophrenics. Schizophrenia Research, 11(3), 239-244. https://doi.org/10.1016/0920-9964(94)90017-5

Addington, D., Addington, J., Maticka-Tyndale, E., & Joyce, J. (1992). Reliability and validity of a depression rating scale for schizophrenics. Schizophrenia Research, 6(3), 201-208. https://doi.org/10.1016/0920-9964(92)90003-N

Addington, D., Addington, J., & Schissel, B. (1990). A depression rating scale for schizophrenics. Schizophrenia Research, 3(4), 247-251. https://doi.org/10.1016/0920-9964(90)90005-R

Addington, J., Shah, H., Liu, L., & Addington, D. (2014). Reliability and validity of the Calgary Depression Scale for Schizophrenia (CDSS) in youth at clinical high risk for psychosis. Schizophrenia Research, 153(1), 64-67. https://doi.org/10.1016/j.schres.2013.12.014

Galletly, C., Castle, D., Dark, F., Humberstone, V., Jablensky, A., Killackey, E., Kulkarni, J., McGorry, P., Nielssen, O., Tran, N. (2016). Royal Australian and New Zealand College of Psychiatrists clinical practice guidelines for the management of schizophrenia and related disorders. Australian & New Zealand Journal of Psychiatry, 50(5), 410-472. doi:10.1177/0004867416641195

Kim, S.-W., Kim, S.-J., Yoon, B.-H., Kim, J.-M., Shin, I.-S., Hwang, M. Y., & Yoon, J.-S. (2006). Diagnostic validity of assessment scales for depression in patients with schizophrenia. Psychiatry Research, 144(1), 57-63. https://doi.org/10.1016/j.psychres.2005.10.002

Lançon, C., Auquier, P., Reine, G., Bernard, D., & Toumi, M. (2000). Study of the concurrent validity of the Calgary Depression Scale for Schizophrenics (CDSS). Journal of Affective Disorders, 58(2), 107-115. https://doi.org/10.1016/S0165-0327(99)00075-0

Müller, M. J., Brening, H., Gensch, C., Klinga, J., Kienzle, B., & Müller, K.-M. (2005). The Calgary Depression Rating Scale for schizophrenia in a healthy control group: Psychometric properties and reference values. Journal of Affective Disorders, 88(1), 69-74. https://doi.org/10.1016/j.jad.2005.04.005