Hi all,

I'm looking into observational studies to try and better characterize treatment-resistant depression. I'm having trouble deciphering the paragraph in bold below, having read it multiple times. What does this mean in plain English? I have provided some additional text for context.

Thanks in advance for your help!

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The study sample began with identifying patients with Major Depressive Disorder and included 572,682 patients with at least one service claim for a depressive disorder including dysthymic disorder.

Patients were excluded if:

a) they had a pre-defined exclusion diagnosis for schizophrenia,

schizoaffective or bipolar disorders

b) the patient’s age on Index Diagnosis Date was not within the 18–64 year age bracket;

c) an Index Diagnosis Date was not found.

The Index Diagnosis Date for each patient was defined as the date of the first inclusion diagnosis that:

1) had no other inclusion diagnosis or prescription claim of antidepressants in the prior 120 days (guided by the definition of a ‘‘new episode’’ contained in PQRI 2007 Measure 9) [19], and

2) had continuous service

eligibility for 4 months prior to and 24 months after the date (to ensure a minimum study period of 2 years for each patient).

Classification of MDD Episode

After patients were included in the study sample, the data were examined and episodes of MDD were established for each patient. An MDD episode was defined to begin on a first relevant date and end 120 days after the last relevant date, where the first relevant date was a date of inclusion diagnosis that was not preceded by any inclusion diagnosis or an antidepressant prescription claim in the preceding 120 days. The last relevant date was a date of inclusion diagnosis or antidepressant prescription claim that was followed by a clear period of 120 days without any inclusion diagnosis or antidepressant claim.