When one dimension is not enough
You sleep badly, your shoulders ache, and you snap at people you like. Ask yourself which of those is the problem and you will not get a clean answer, because they usually arrive together. The Symptom Checklist-90 (SCL-90) was built for exactly that situation: instead of scoring one construct, it scans 90 symptoms at once and then tells you where they cluster.
Leonard Derogatis and colleagues published the preliminary report in 1973, when the checklist was still under development. The nine dimensions are still the ones in use today.
What the 90 items cover
Each item is a symptom, rated for the past seven days on five levels: not at all, a little bit, moderately, quite a bit, extremely. On this site that runs from 0 to 4.
| Dimension | Items | What it picks up |
|---|---|---|
| Somatization | 12 | Body complaints that do not have a clear medical explanation: headaches, back and muscle pain, cardiovascular, stomach and breathing symptoms. |
| Obsessive-compulsive | 10 | Thoughts, urges and actions you experience as unwanted and hard to stop, plus trouble with memory and concentration. |
| Interpersonal sensitivity | 9 | Feeling inadequate next to other people, self-consciousness, discomfort in company, expecting rejection. |
| Depression | 13 | Low mood, loss of interest and energy, hopelessness, and thoughts about ending your life. |
| Anxiety | 10 | Restlessness, nervousness, tension, trembling, panic, and feelings of unreality. |
| Hostility | 6 | Irritability, urges to break things, arguments, temper outbursts. |
| Phobic anxiety | 7 | Fear of travel, open spaces, crowds, public places and social situations. |
| Paranoid ideation | 6 | Suspicion, hostility, feeling watched or talked about, grandiosity. |
| Psychoticism | 10 | A broad sample of unusual experiences, from feeling isolated to thoughts being controlled or broadcast. |
Seven more items (19, 44, 59, 60, 64, 66 and 89) ask about sleep and appetite. They do not belong to any dimension, and the Chinese scoring convention treats them as a tenth factor so that the parts add up to the total.
Three summary numbers
The Global Severity Index (GSI) is the average of all 90 answers, so it runs from 0 to 4 and answers the question "how much symptom is there overall". The Positive Symptom Distress Index (PSDI) averages only the items you rated above zero, which makes it a measure of intensity rather than breadth. The Positive Symptom Total (PST) counts how many items you rated above zero, which is a measure of breadth rather than intensity.
The GSI is the number most reports lead with, and the bands below are the ones printed with the Chinese version:
| GSI | Reading |
|---|---|
| 0 to 0.5 | No symptoms from the list reported. |
| 0.5 to 1.5 | Symptoms present but infrequent. |
| 1.5 to 2.5 | Mild to moderate. |
| 2.5 to 3.5 | Moderate to severe. |
| 3.5 to 4 | Both frequency and intensity are high. |
Where the dimensions came from
Five of the nine dimensions were validated across a series of clinical investigations covering over 2,500 patients before the 1973 report. The last four were provisional at that point, and the paper says so plainly: hostility and phobic anxiety had partial empirical support, while paranoid ideation and psychoticism were still being tested. Those four have since accumulated their own evidence, but the ordering matters if you read the original paper.
The scale came out of drug trials. The SCL was designed as a criterion measure for psychotherapy medication studies, and the first five dimensions were shown to respond to antipsychotics and antidepressants. That is why it covers so much ground: it was meant to detect change across a wide range of symptoms, not to pin down a single diagnosis.
Reliability
Internal consistency across the nine scales runs from 0.77 to 0.90, and test-retest reliability over a one-week interval runs from 0.80 to 0.90. The original administration estimate was about 20 minutes of patient time plus five minutes for a technician.
Chinese norms, and a trap worth knowing
The Chinese version ships with factor means for normal adults: somatization 1.37, obsessive-compulsive 1.62, interpersonal sensitivity 1.65, depression 1.50, anxiety 1.39, hostility 1.46, phobic anxiety 1.23, paranoid ideation 1.43, psychoticism 1.29, with standard deviations between 0.41 and 0.61.
Those figures are on the Chinese version's 1 to 5 scale, where the lowest option scores 1 rather than 0. This site scores from 0, so subtract 1 from each norm before comparing it with your own factor scores. Skipping that step makes an ordinary score look almost a full point above average. The same convention applies to the rule of thumb that a factor score above 2 signals a problem, which is a 1 on this site's scale.
For a second reference point, a Danish normative study used a T-score of 63 as the threshold for clinically significant symptoms.
What it does not do
The Chinese version's instructions state the limits directly: the SCL-90 is not suitable for mania or schizophrenia. Coverage and precision trade off against each other, and 90 items spread across nine dimensions cannot tell you which diagnosis fits. A high score means the symptoms are worth a conversation with a professional, not that a particular condition is present.
One item deserves a note. Item 15 asks about thoughts of ending your life and belongs to the depression dimension. If you endorse it, the score is not the important part.
Take the test
The CheckPsych version uses the 90 original items and takes about 15 to 20 minutes. You get the GSI with its band, the nine factor means, the PSDI and the PST.
References
Derogatis, L. R., Lipman, R. S., & Covi, L. (1973). SCL-90: An outpatient psychiatric rating scale, preliminary report. Psychopharmacology Bulletin, 9(1), 13-28.
Derogatis, L. R. (1994). SCL-90-R: Administration, scoring and procedures manual (3rd ed.). NCS Pearson.
Jensen, H. H., Mortensen, E. L., & Lotz, M. (2013). SCL-90-R symptom profiles and outcome of short-term psychodynamic group therapy. ISRN Psychiatry, 2013, 540134.
Gomez, R., Stavropoulos, V., Zarate, D., & Palikara, O. (2021). Symptom Checklist-90-Revised: A structural examination in relation to family functioning. PLOS ONE, 16(3), e0247902.
Disclaimer: this article and the SCL-90 are for education and self-reflection. They are not a diagnosis. Symptom counts move with physical illness, medication, sleep and stress, which is one reason a clinician will ask about all of those before drawing conclusions. If your GSI lands in the moderate to severe range, or if any item about self-harm applies to you, please talk to a qualified professional.