Brief Symptom Inventory-18

The Brief Symptom Inventory-18 (BSI-18), developed by Derogatis in 2001 from SCL-90 and BSI-53, is a brief mental health screening tool. Its 18 items assess somatization, depression, and anxiety and take about 5 minutes. Widely used in several countries, it is concise, easy to administer, and adaptable across cultures. It suits rapid screening in communities, initial clinical assessment, and tracking treatment outcomes.

This site's BSI-18 version uses five ratings from 1 (none) to 5 (severe). Each of the three dimensions—somatization, depression, and anxiety—is the average of its six items. The report also shows: GSI (Global Severity Index), the average of all 18 items; PST (Positive Symptom Total), the number of items scored above 1; and PSDI (Positive Symptom Distress Index), the average score of those positive items, or 0 if there are none. The current calculator displays dimension averages below 1.5 as within its reference range, 1.5 to under 2.5 as mild, 2.5 to under 3.5 as moderate, and 3.5 or above as severe. It flags a result for attention when GSI is at least 1.5 or PST is at least 6. These are the display rules used by this site's implementation, not a diagnosis. The standard 0–4 format cited in the source material differs from the 1–5 ratings used here. No T-score conversion is performed, so standard-version scores or T-score screening rules should not be used to interpret these raw results directly.

BSI-18 suits adults aged 18 and above for community screening, initial clinical symptom assessment, monitoring psychotherapy or medication outcomes, and research. Its brevity makes it useful when time is limited or repeated measurement is needed. Use the broader SCL-90 when a detailed assessment of more symptom areas is required.

Both are symptom screening tools developed by Derogatis. BSI-18 has 18 items taking about 5 minutes; SCL-90 has 90 taking about 20. BSI-18 covers three core areas—somatization, depression, and anxiety—while SCL-90 covers nine. Choose BSI-18 for a quick view of core symptoms or repeated measurements; choose SCL-90 for a comprehensive view, including obsessive-compulsive symptoms, interpersonal sensitivity, or hostility.

① Somatization: physical discomfort such as dizziness, chest pain, nausea, breathing difficulties, numbness, or weakness, often associated with psychological stress. ② Depression: low mood, reduced interest, loneliness, worthlessness, and hopelessness, sometimes with suicidal thoughts when severe. ③ Anxiety: tension, nervousness, sudden fear, panic attacks, or restlessness. These are common, core manifestations of mental health difficulties.

In this site's implementation, a dimension average of 2.5 or above receives a moderate or severe label, and a GSI of 1.5 or above prompts attention to the result. The calculator also flags results with at least 6 positive items, defined here as ratings above 1. These are website report rules and do not establish a clinical diagnosis. Consider professional assessment if symptoms trouble you, especially when depressed mood includes suicidal thoughts, anxiety includes panic attacks, physical symptoms remain unexplained after medical examination, or symptoms last more than two weeks and seriously affect daily life, work, or study. Seek help immediately for suicidal thoughts. Significant distress warrants support even if the site's score labels are low. This version reports raw 1–5 averages and does not calculate standardized T-scores; standard 0–4 or T-score screening criteria cannot be applied directly to its results.