Participants in this observational study will only undergo sequential cognitive performance evaluations by examiner- administered cognitive test battery.

The WLRT used for the computerized test battery that measures person's ability to encode, consolidate, store, and retrieve verbal information and is a sensitive test of verbal learning and memory in a variety of disease states, including MDD. The memory test will include a list of 15 words presented aloud, one at a time, through the iPad. After the 15-word list is presented, the participant will be asked to verbally recall as many of the words as possible. The 15 word list and participant recall will be conducted 4 more times (total 5 times). After the 5th learning trial and recall, performance on the learning trials of the original word list and on the delayed recall will be considered as the primary scores. The participant's responses during the WLRT will be recorded and scored using 2 methods: by the speech recognition engine (SRE) and by an on-site test supervisor who will record the responses directly on the Revere.D application from a touch screen on the iPad.

The VBRT is based on a visuospatial learning test that requires participants to recall the location of colored tiles within an onscreen grid. Performance on visuospatial recall tasks has been shown to be lowered in anxious, depressed, or older healthy participants, as well as in participants with mild traumatic brain injury, schizophrenia, and acquired immune deficiency syndrome (AIDS) dementia complex. The participant is shown a sequence of on screen grids on which an increasingly complex pattern of colored tiles is depicted. Each pattern displays for only a brief period (0.5 seconds), after which participants are asked to recall the pattern. Recall accuracy (the number of correctly recalled patterns) is recorded by computerized cognitive test battery.

The SDMaT measures the time to pair abstract symbols with specific numbers. The test includes a coding key consisting of 9 abstract symbols, each paired with a number ranging from 1 to 9. Following the key, the participant is presented with randomly ordered symbols and is required to enter the number corresponding to each symbol as fast as possible using a keypad. The number of correct digit entries within 90 seconds is recorded by computerized cognitive test battery .

The computerized (Revere.D) version of the TMT-B is modeled after the paper-and-pencil version of the test. The TMT-B measures divided attention and executive function (tracking and sequencing). The participant is instructed to draw a line to connect a set of 25 consecutively numbered and lettered circles, alternating sequentially between numbers and letters (that is, 1 A 2 B). The participant is instructed to work as quickly as possible while still maintaining accuracy. The TMT-B has acceptable reliability; reliability coefficients have typically been reported as exceeding 0.65. The TMT-B is sensitive to cognitive decline associated with MDD.

The BMT used in this study is modeled after published maze learning tests, such as the Groton Maze Learning Test, that assess processing speed, working memory, spatial learning, and error monitoring. In the BMT, the participant learns over 13 trials to navigate a path across tiles from a starting position to a target position using a set of predefined rules. The primary measure is total number of errors made in the 3 trials; the total time required for correct completion of the 3 trials will be used as a secondary score that will be evaluated by computerized cognitive test battery.

The RAVLT is a commonly used measure of a person's ability to encode, consolidate, store, and retrieve verbal information and is a sensitive test of verbal learning and memory in a variety of disease states, including MDD. The test will be administered by an examiner who will read the words aloud to the participant . The memory test will include a list of 15 words presented one at a time verbally by the examiner. After the 15-word list is presented, the participant will be asked to verbally recall as many of the words as possible. The 15 word list and participant recall will be conducted 4 more times (total 5 times). After the 5th learning trial and recall performance on the learning trials of the original word list and on the delayed recall will be considered as the primary scores that will be evaluated by examiner-administered cognitive test battery.

The BVMT-R is a test of visual learning and recall. Participants are presented with 6 geometric figures in a 2*3 visual array; presentation is on a sheet of paper for a 10 second exposure. Participants are asked to draw as many figures in their proper locations as they remember, for each of 3 learning trials. The test has good test-retest reliability; r [greater than (>)]0.96 for the learning trials. The BVMT-R is included in the MATRICS Consensus Cognitive Battery. The total recall score will be used in this study that will be evaluated by examiner-administered cognitive test battery.

The SDMT is a widely used, paper-and-pencil assessment of complex scanning and visual tracking, requiring elements of attention, visuoperceptual processing, working memory, and cognitive/psychomotor speed.The test is viewed as a robust screening test for adult neuropsychological impairment and has been used to demonstrate worse cognitive functioning in patients with MDD. The SDMT measures the time to pair abstract symbols with specific numbers. The test includes a coding key consisting of 9 abstract symbols, each paired with a number ranging from 1 to 9. Following the key, the participant is presented with randomly ordered symbols and is required to write the number corresponding to each symbol as fast as possible. The number of correct substitutions within 90 seconds is recorded by examiner-administered cognitive test battery.

The NAB-MT is a test in which participants are asked to complete 7 increasingly complex paper-and-pencil mazes; scores include time to completion.The test assesses aspects of executive function, especially planning and foresight. It was standardized on a sample of more than 1,400 healthy adults. Extensive validation evidence has been established through exploratory and confirmatory factor analyses, criterion validity investigations, and several clinical validation studies. It has been used to demonstrate neurocognitive impairments in patients with depression. The NAB-MT is included in the MATRICS Consensus Cognitive Battery. The time to completion score will be used in this study that will be evaluated by examiner-administered cognitive test battery.

WCST is a widely used measure of executive function. WCST requires the participant to sort symbols based on symbol features such as color, shape and number without providing instructions as to matching criteria; rather the participant is provided feedback whether a particular match is right or wrong. Responses will be scored for Categories Achieved and Percent Perseverative Errors by examiner-administered cognitive test battery.