The QIDS-SR16 is a widely used self-report scale for depressive symptoms, containing 16 items that cover all core symptom criteria for DSM-IV major depression. This scale was developed by Rush et al. for rapid assessment of depression symptom severity. Each item has 4 options with a scoring range of 0-3 points, where 0 = no symptoms or mildest symptoms, and 3 = most severe symptoms. The scale demonstrates good internal consistency (Cronbach's α = 0.86) and exhibits high sensitivity for detecting symptom fluctuations.

THINC-it® is a comprehensive, digitally-based cognitive screening instrument specifically designed to assess cognitive dysfunction in adults with major depressive disorder (MDD). This validated tool comprises five integrated components: four objective cognitive tests (Codebreaker, Trials, Spotter, and SymbolCheck) that evaluate processing speed, executive function, attention, and working memory, plus the PDQ-5-D self-report questionnaire for subjective cognitive assessment. The entire battery requires approximately 10-12 minutes to complete and demonstrates robust psychometric properties with high sensitivity to cognitive changes over time.

The Snaith-Hamilton Pleasure Scale (SHAPS) is a 14-item self-report instrument designed to assess anhedonia (reduced capacity to experience pleasure) in clinical and research settings. Each item is rated on a 4-point Likert scale (1-4), yielding a total score range of 14-56, where higher scores indicate greater levels of anhedonia. The scale demonstrates excellent internal consistency with Cronbach's alpha values ranging from 0.84 to 0.88 and shows satisfactory test-retest reliability (ICC=0.70).

The Hamilton Anxiety Rating Scale (HAMA) is a 14-item clinician-administered instrument developed by Hamilton in 1959 to assess anxiety symptom severity in clinical populations. Each item is rated on a 5-point scale (0-4), with total scores ranging from 0-56, where higher scores indicate greater anxiety severity. Score interpretation follows established cutoffs: 0-17 (mild anxiety), 18-24 (mild to moderate anxiety), and 25-30 (moderate to severe anxiety) . The scale demonstrates excellent internal consistency reliability with Cronbach's alpha values consistently ranging from 0.77 to 0.92.

The Pittsburgh Sleep Quality Index (PSQI) is a self-report questionnaire designed to assess sleep quality and disturbances over a one-month period. The scale comprises seven component scores: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleep medication, and daytime dysfunction. Each component is scored from 0-3, yielding a global PSQI score ranging from 0-21, where higher scores indicate poorer sleep quality. A global score >5 typically indicates poor sleep quality, while a cutoff of 8 demonstrates optimal sensitivity (0.90) and specificity (0.83) for detecting sleep disturbances. The PSQI demonstrates good psychometric properties with Cronbach's alpha coefficients ranging from 0.64 to 0.89.

The 36-Item Short Form Health Survey (SF-36) is a measure of health-related quality of life consisting of 36 items that assess eight health domains: physical functioning, role limitations due to physical health, bodily pain, general health perceptions, vitality, social functioning, role limitations due to emotional problems, and mental health. Items are scored using various response scales (dichotomous, 3-point, 5-point, and 6-point), with domain scores ranging from 0-100, where higher scores indicate better health status. The Cronbach's alpha of the SF-36 ranges from 0.70 to 0.94.

The World Health Organization Quality of Life Assessment - Brief Version (WHOQOL-BREF) is a comprehensive 26-item self-report instrument that evaluates quality of life within the context of an individual's culture, value systems, personal goals, and standards. The scale comprises four domains: Physical Health (7 items), Psychological (6 items), Social Relationships (3 items), and Environment (8 items), plus two additional items assessing overall quality of life and general health. Each item is rated on a 5-point Likert scale, with domain scores transformed to a 0-20 scale or alternatively to a 0-100 scale for standardized comparison. The Cronbach's alpha coefficients of the WHOQOL-BREF ranges from 0.70 to 0.896.