What is the Score on the Self-Rating Depression Scale?

Level 1: The Mechanics of the Scale — How is the Score Generated?

To understand a score, one must first understand its calculation. The genius of the SDS design lies in its attempt to convert an individual's subjective experience over the past week into a comparable, objective metric through a standardized process.

The Bedrock: 20 Items

The SDS consists of 20 statements, each describing a feeling or behavior related to depression. These items cover the core symptom clusters defined by the World Health Organization (WHO) and the American Psychiatric Association (APA), primarily including four aspects:

• Affective Symptoms: e.g., "I feel down-hearted and blue" (Item 1), "I have crying spells or feel like it" (Item 3). This is the core experience of depression.
• Somatic Symptoms: e.g., "I have trouble sleeping at night" (Item 4), "I find my weight is decreasing" (Item 7), "My heart beats faster than usual" (Item 9). These symptoms reflect the physical manifestation of psychological issues.
• Psychomotor Symptoms: e.g., "I am restless and can't keep still" (Item 13), reflecting inner anxiety and tension.
• Psychological Symptoms: e.g., "I feel that the future is hopeful" (Item 14), "I feel that I am useful and needed" (Item 17), "I feel that others would be better off if I were dead" (Item 19). This part touches on deep psychological activities like cognition and self-worth.

The Core of Scoring: Four-Point Scale and Reverse Scoring

Each item uses a four-point Likert scale, asking the respondent to choose based on the frequency of the symptom in the past week. However, 10 of the items are "negative" statements (describing depressive symptoms), and 10 are "positive" statements (describing a healthy state). To ensure all items point in the same direction (higher score = more severe depression), the scale uses Reverse Scoring for the 10 positive statements (items 2, 5, 6, 11, 12, 14, 16, 17, 18, 20). For these items, an original choice of 1, 2, 3, or 4 is converted to 4, 3, 2, or 1, respectively.

From Raw Score to Standard Score: The Meaning of 1.25

After all 20 items are scored, they are summed to get a Raw Score (ranging from 20 to 80). This is rarely used directly. To make it more intuitive, it is converted to a Standard Score (the final score you see) using a simple formula:

This multiplication converts the 20-80 range to a more familiar 25-100 range, creating an easier-to-understand "depression index."

Level 2: Clinical Interpretation — The Warning Signal Behind the Numbers

A standard score, say 65, needs context. This is where clinical interpretation comes in. It's crucial to remember this is for screening, not diagnosis.

The Cut-off Scores: From Quantity to Quality

Through extensive clinical data, researchers have established cut-off points to differentiate levels of depression. The most commonly used standard in China, after localization, is as follows:

The Score is a "State," Not a "Trait"

A core principle: the SDS measures a "state" (your condition over the past week), not a "trait" (a stable personality characteristic). A high score doesn't mean "you are a depressive person"; it means "you have experienced a certain level of depressive symptoms in the past week." This distinction is vital to avoid self-labeling and to emphasize the potential for change.

Level 3: The Scientific Foundation — Why Can We (Conditionally) Trust This Score?

Any measurement tool must pass two core tests to be scientifically accepted: Reliability and Validity.

Reliability: The Stability and Consistency of the Score

Reliability asks, "Is this scale dependable?" The SDS performs well here:

• Test-Retest Reliability: Scores are stable over short periods, with correlation coefficients typically between 0.7 and 0.9.
• Internal Consistency Reliability: The items work together harmoniously to measure "depression." The Cronbach's alpha coefficient is consistently above 0.80, which is considered excellent.

Validity: Does the Score Accurately Measure "Depression"?

Validity asks the deeper question: "Does this scale measure what it claims to measure?"

• Content Validity: The items adequately cover the core dimensions of depression recognized by diagnostic standards.
• Criterion-Related Validity: SDS scores correlate highly with clinical diagnoses from psychiatrists and scores from other authoritative depression scales (like the HAM-D).

Level 4: Deep Structure Analysis — The Symptom Dimensions Behind the Score

A total score can flatten information. Two people with the same score of 65 might have vastly different experiences. Using a statistical technique called Factor Analysis, we can look inside the SDS "black box" to find underlying dimensions.

Studies typically identify several core factors:

• Affective Factor: The core of depression, including items on sadness, crying, and irritability.
• Somatic Factor: The physical expression of depression, including items on sleep, appetite, fatigue, and heart rate. This is particularly important for identifying "somaticized" depression, where physical complaints are primary.
• Cognitive Factor: Focuses on changes in thinking, including items on hope, self-worth, and meaning in life.
• Psychomotor Factor: Pertains to restlessness or slowdown in activity.

Understanding this structure allows for a more personalized interpretation, moving from "how high" the score is to "what constitutes" the score.

Level 5: Critical Examination — Rational Boundaries and Wise Application

Every tool has its limits. We must examine the SDS's shortcomings with the same rigor.

The Path to Wise Application

Considering all levels of analysis, here is a clear, rational guide:

1. Positioning: It is a "screening tool," not a "diagnostic instrument." It's a smoke alarm, not a firefighter. Never self-diagnose based on the score.
2. Perspective: View it as a "starting point for a conversation," not a "final verdict." A high score is an invitation to look deeper and speak with a professional.
3. Method: Look at the "details," not just the "total score." Which items drove your score up? The details contain far more information than the final number.
4. Action: Seek "professional validation," not "self-diagnosis." If you are concerned, the most responsible action is to take your results to a psychiatrist or a trained psychotherapist for a comprehensive evaluation.