Z Distribution
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Z Distribution
Definition
▶ Standard Normal (Z) Distribution
The Zung Depression Inventory (SDS) is a 20-item self-rating scale concerning affective, cognitive, behavioral, and somatic symptoms of depression (Zung, 1965). Half of the items are worded positively, half are phrased negatively. The scale was developed on the basis of the most commonly found diagnostic criteria of depression and patient interviews. Subjects rate each item according to how they felt during the preceding week. The response categories range from (1) “none or a little of the time” to (4) “most or all of the time.” The scale takes on average 5 min to complete. An index for the SDS is derived by summing the item scores. This summary score is then divided by a maximum possible score of 80. The SDS index ranges from 0.25 to 1. The following cutoffs are recommended by the author of the scale: Individuals with an index below 0.62 are considered normal, with an index of 0.62–0.74 are considered to suffer from a mild depression, and with an index of 0.75–0.86 are considered to suffer from a moderate to marked depression. Indices of 0.87 and above indicate severe depression. The SDS is available in about 30 languages. The little available data examining the reliability of the SDS reveals satisfactory split-half reliability (r ¼ 0.73) and internal consistency (Cronbach’s alpha ¼ 0.79). Concurrent validity of the scale could be demonstrated by correlating the SDS with other standardized self-rating scales of depression like the Beck Depression Inventory
Zoloft ® ▶ Selective (SSRIs)
Serotonin
Reuptake
Inhibitors
Z-Score ▶ Standard Normal (Z) Distribution
Zung Depression Inventory Maria Kleinst€auber Department of Clinical Psychology and Psychotherapy, Johannes Gutenberg-University of Mainz, Mainz, Germany
Synonyms Zung depression rating scale (ZDRS); Zung depression scale; Zung self-assessment depression scale; Zung self-rating depression scale (SDS)
M.D. Gellman & J.R. Turner (eds.), Encyclopedia of Behavioral Medicine, DOI 10.1007/978-1-4419-1005-9, # Springer Science+Business Media New York 2013
Z
2086
and the Depression Scale of the Minnesota Multiphasic Personality Inventory. Results of correlations between the SDS and clinicianrated instruments like the Hamilton Rating Scale for Depression are less consistent. Factor analyses of the SDS revealed three main factors: positive symptoms/well-being, negative effect, and somatic symptoms. Sensitivity of the SDS in differentiating between depressed and nondepressed subjects was found to be adequate. The influence of different demographical variables on the SDS index was also examined. There seem to be higher SDS scores for individuals being older than 64 or younger than 20 years in non-patient groups. Associations between SDS score and age in psychiatric populations could not be demonstrated clearly. Women in patient as well as non-patient groups seem to have slightly higher scores than males. Furthermore, SDS scores are slightly negatively correlated with education (range: r ¼ .08 to .2
