6 - (IOP 3) Predicting Difficult-to-treat Depression Before It Becomes Treatment Resistant

There has been longstanding interest in defining and investigating treatment resistant depression (TRD). It is common to classify depressed patients who have not responded to multiple pharmacologic treatment efforts as treatment resistant. Recently, it has been recommended that the TRD be reconceptualized as difficult to treat depression (DTD). This shift emphasizes the importance of a broader conceptualization that requires a more comprehensive assessment and shifts the focus of treatment from a curative/remission model to a disease management model emphasizing functioning and quality of life rather than symptom elimination. It also makes identification of DTD possible prior to failed medication trials. The current study validates of the first self-report scale of DTD, the Difficult to Treat Depression Questionnaire (DTDQ), and assesses its ability to predict DTD prior to treatment failure.

Patients from a partial hospital program (N = 920) completed the DTDQ, including one item assessing the number of prior failed treatment episodes, prior to treatment. Patients also completed the Remission from Depression Questionnaire (RDQ) at admission and discharge from a partial hospital program as a measure of overall symptoms/functioning, depressive symptoms, non-depressive symptoms, coping ability, positive mental health, functional impairment, and quality of life. Analyses examined psychometric characteristics of the DTDQ, concurrent and predictive validity of the DTDQ, and compared the predictive validity of the DTDQ and multiple failed treatment episodes. These analyses were then replicated using a smaller subsample (n = 211) who did not have multiple prior episodes of treatment failure to examine the predictive validity of the DTDQ in characterizing treatment resistance prior to meeting criteria for TRD.

The DTDQ demonstrated excellent internal consistency and test-retest reliability. Greater scores on the DTDQ were associated with greater symptomatology and worse functioning on all RDQ subscales at admission, discharge, and discharge after controlling for scores at admission. The DTDQ was significantly associated with outcomes after controlling for the number of failed trials, but the number of failed trials did not predict outcome after controlling for DTDQ scores. Patients with DTD according to the DTDQ (highest 25% of sample) demonstrated greater symptomatology and functioning on all RDQ scores at admission, discharge, and discharge controlling for admission RDQ. Results were largely comparable, but only extended to the overall symptomatology/functioning, greater levels of depressive and non-depressive symptoms, and worse coping ability subscales when examining the relationship between DTD and RDQ scores at discharge when controlling for RDQ scores at admission.

The DTDQ is a reliable and valid measure of the recently introduced construct of DTD and has good predictive validity. The DTDQ captures important prognostic information related to DTD beyond that accounted for by the number of medication trial failures. Critically, the DTDQ can be used to prospectively identify depressed patients who meet criteria for DTD before they begin their first treatment episode.