One group pre-test post-test design with 2 weeks of placebo followed by up to 3 weeks of treatment.
A data frame with 250 observations on the following 7 variables.
Hamilton Depression Index
time of measurement in weeks from 0 to 4: 0 is begining of study, 1 is end of 1st placebo week, 2, 3, 4 are at end of treatment weeks
a factor with levels
Plasma log concentration of IMI
Plasma log concentration of DMI – an IMI metabolite
a factor with levels
From Hedeker: http://www.uic.edu/classes/bstt/bstt513/Kaplan http://tigger.uic.edu/~hedeker/long.html
Structure: Longitudinal, up to 5 occasions on 66 depressed subjects
To illustrate an HLM application, we will consider data from a psychiatric study described in Reisby et al. (1977). This study focused on the longitudinal relationship between imipramine (IMI) and desipramine (DMI) plasma levels and clinical response in 66 depressed inpatients. Imipramine is the prototypic drug in the series of compounds known as tricyclic antidepressants and is commonly prescribed for the treatment of major depression (Seiden & Dykstra, 1977). Because imipramine biotransforms into the active metabolite desmethylimipramine (or desipramine), measurement of desipramine was also done in this study. Major depression is often classified in terms of two types. The first type, nonendogenous or reactive depression, is associated with some tragic life event such as the death of a close friend or family member, whereas the second type, endogenous depression, is not a result of any specific event and appears to occur spontaneously. It is sometimes held that antidepressant medications are more effective for endogenous depression (Willner, 1985). In this sample, 29 patients were classified as nonendogenous, and the remaining 37 patients were deemed to be endogenous.
The study design was as follows. Following a placebo period of 1 week, patients received 225-mg/ day doses of imipramine for 4 weeks. In this study, subjects were rated with the Hamilton depression (HD) rating scale (Hamilton, 1960) twice during the baseline placebo week (at the start and end of this week), as well as at the end of each of the 4 treatment weeks of the study. Plasma level measurements of both IMI and its metabolite DMI were made at the end of each treatment week. The sex and age of each patient were recorded, and a diagnosis of endogenous or nonendogenous depression was made for each patient. Although the total number of subjects in this study was 66, the number of subjects with all measures at each of the weeks fluctuated: 61 atWeek 0 (start of placebo week), 63 at Week 1 (end of placebo week), 65 at Week 2 (end of first drug treatment week), 65 at Week 3 (end of second drug treatment week), 63 at Week 4 (end of third drug treatment week), and 58 at Week 5 (end of fourth drug treatment week). Of the 66 subjects, only 46 had complete data at all time points. Thus, complete case analysis under repeated-measures MANOVA, for example, would discard approximately one third of the data set. HLM, alternatively, uses the data that are available from all 66 subjects.
Note from http://healthnet.umassmed.edu/mhealth/HAMD.pdf Hamilton Scale goes from 0 to 60 For the 17-item version, scores can range from 0 to 54. One formulation suggests that scores between 0 and 6 indicate a normal person with regard to depression, scores between 7 and 17 indicate mild depression, scores between 18 and 24 indicate moderate depression, and scores over 24 indicate severe depression.
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