Dallas 2K: A Natural History Study of Depression (D2K)

  • End date
    Sep 13, 2026
  • participants needed
  • sponsor
    University of Texas Southwestern Medical Center
Updated on 13 June 2022
medication treatment
HIV Infection
substance use
bipolar disorder
depressive disorder
psychiatric disorder
depressed mood
mood disorder
dysthymic disorder
schizoaffective disorder
psychiatric treatment
structured diagnostic interview
psychiatric therapy
Accepts healthy volunteers


The Dallas 2K is a 10-year natural history, longitudinal, prospective study of a cohort of 2,000 participants that will help uncover the socio-demographic, lifestyle, clinical, psychological and neurobiological factors that contribute to anti-depressant treatment response: remission, recurrence, relapse and individual outcomes in depressive disorders. Hence, the expected duration of this study is 20 years in length. Since this is an observational study, investigators will explore a comprehensive panel of carefully selected participant specific parameters: socio-demographic (age, ethnicity, economic); lifestyle (physical activity, substance use); clinical (medical history, anxious depression, early life trauma), biological (biomarkers in blood, saliva, urine), behavioral (cognitive, emotional), neurophysiological (EEG), and neuroimaging (structural, functional brain circuitry) with the goal to develop the most robust predictive models of treatment response and of depression outcomes. There is no medication or non-medication treatment or intervention provided by this study.

Subjects will have elevated symptomatology of nonpsychotic chronic or recurrent depressive disorder and will be currently receiving or will be prescribed standard of care medication or non-medication based treatments by their providers/clinicians. The study cohort will reflect the wide range of patients seen in typical primary or psychiatric care settings, and may include unipolar or bipolar disorders and dysthymia (a more chronic form of depression). The cohort will be broadly representative of and generalizable to the US general population as a whole.


This is a non-randomized, natural history, non-treatment, longitudinal cohort study. Participants will be receiving standard of care treatment for depression and other comorbidities from their treating clinician and will be allowed to continue such treatments in this study. There are no experimental study procedures, other than methods used for data capture (questionnaires, blood collection, EEG and MRI). Participants will be expected to visit study site (s) for repeated collection of data (assessments, biospecimens, and imaging procedures), up to 4 times a year for 10 years. A reduced battery of tests is allowable if subject is not able or willing to complete the full battery after the baseline visit.

2000 research participants will be enrolled and followed over an eight-year period (each participant will be followed for 10-years) with collection of clinical and depression measurement assessments, measurement of vital signs, collection of biospecimens for biochemical and genetic analyses, electroencephalogram (EEG) with behavioral assessments, and neuroimaging using magnetic resonance imaging (MRI). Skin punch biopsy will be performed in a sub-set of the research cohort, defined as demonstrating a heritable phenotype of depression. Stool sample will be performed in a sub-set of the research cohort, defined as demonstrating a heritable phenotype of depression.

Participants will complete PHQ-9 (Patient Health Questionnaire-9), a brief self-administered measure of depression severity, and PS (Psychosis Screening) questionnaire, as part of inclusion and exclusion criteria, respectively. Participants will then complete all required computer-assisted self-rating and clinician-administered instruments. The self-rating instruments are expected to take approximately 2.5 hours using an iPad or laptop computer, and will collect detailed socio-demographic, life habits, family and medical history, and depression severity and treatment history. After completing the questionnaires, the research personnel will measure the subject's blood pressure, height, waist and hip circumference and weight. The subject will then provide blood, saliva and urine samples (morning blood draw appointments will be offered whenever participants agree to fast before blood draws but non-fasting blood will also be collected, when not possible to obtain fasting blood).

For study assessments, specimen collection; and EEG and behavioral phenotyping, Dallas 2K study participants will require a 6-hour study visit to UT Southwestern. Participants will be given the option to split their visit into two if that is more convenient, and visit 2 will be used to perform EEG and behavioral assessments. Participants choosing the initial visit at an MDN clinician's office will complete screening, assessments and biospecimen collection at the MDN office but may require a 3-hour visit to UT Southwestern clinics for EEG and behavioral assessments. The MRI may be performed during a separate 2-hour visit to UT Southwestern MRI facility.

Schedule of study visits, procedures and duration:

Study A - Assessments and Questionnaires, 3 hours; Study B - EEG and Behavioral Phenotyping, 3 hours; Study C - Neuroimaging (MRI), 2 hours; Study D - Sub-Study only: Skin punch biopsy, 30 minutes; Study E - Sub-Study only: Stool Sample, 15 minutes; Study F - Sub-Study only: mHealth, Continuous monitoring via a wristband (i.e. fitbit) and/or mhealth application downloaded on a Android operating smartphone.

Studies A and B can be combined into a single 6-hour visit when occurring at UT Southwestern.

EEG and behavioral phenotyping and Neuroimaging will be performed at 3-month intervals.

For participants in the optional sub-study, skin punch biopsy, Study D will be performed during any one of the other visits, depending on participants' convenience.

For participants in the optional sub-study stool sample, study E will be performed up to 4 visits per year for 10-years.

For participants in the optional sub-study mhealth study, Study F will be a continuous monitoring of your physical activity, sleep patterns etc. via a wristband (i.e. Fitbit) and/or mHealth application downloaded onto an Android operating Smartphone.

In addition, monthly remote assessments are completed between onsite visits starting from the baseline visit.

Study A will then be repeated at 3-month intervals for up to 4 times a year, during follow-up study visits.

Phlebotomy Procedures Blood samples will be collected from participants by trained phlebotomists, who will draw the sample using standard venipuncture procedures, through a single venipuncture using a small gauge needle. Universal precautions will be observed by the phlebotomists during all draws. The sample collection tubes, priority and volume collected are indicated in the protocol. Each tube will be labeled and packaged for processing and storage.

Electrophysiology (EEG) Procedures: Participants will undergo electrophysiology measures at baseline and at 3-month intervals. Procedures for each of these measures are outlined below. Detailed EEG procedures will be described in the EEG and Behavioral Tasks Procedures Manual, respectively. The EEG markers in this study can be divided into three groups. Participants will first undergo resting EEG. Resting EEG is measured during four, 2 minute periods, half the time with the participants' eyes open, and the other half with the participants' eyes closed. The second EEG measure will specifically localize theta activity using a technique called Low Resolution Electromagnetic Tomography (LORETA). Finally, participants will have head-phones placed, and will be presented with 1000 Hz tones at 5 different intensity levels. The loudness dependency of auditory evoked potential (LDAEP) will be measured during this time. The total time estimate for completion of the EEG collection at each visit is approximately 2 hours. The EEG workgroup will ensure that adequate training, standardization of measures, and validation of equipment is maintained for data consistencies and quality control purposes.

Behavioral Phenotyping: The investigators will administer five distinct tasks to participants, to assess four domains: 1) psychomotor slowing, 2) cognitive control, 3) working memory, and 4) reward responsiveness. To assess these domains, the investigators plan to administer the following tasks: psychomotor slowing, Choice RT task (~5 min) and word fluency task (~5 min); cognitive control, the Flanker task (~10 min); working memory, the A not B task (~10 min); and reward responsiveness, the Probabilistic Reward task (~10 min). This task measures the subject's ability to modify behavior in response to rewards. On each trial, the subject sees a cartoon face with a short or long mouth. The task is to indicate whether a short or long mouth was presented by pressing one of two buttons. Critically, the size difference between the short and long mouths is very small, and correct responses of one type (e.g., short mouth) are followed by monetary rewards three times more frequently than correct responses of the other type (e.g., long mouth). The primary dependent measure is response bias: the degree to which the subject preferentially chooses the response that is more frequently rewarded (in this example, short mouth vs. long mouth). Other dependent measures include RT and a measure of the subject's ability to discriminate between the mouth sizes (28). All tasks will be presented using Eprime software, under standardized procedures across sites. The Behavioral Phenotyping workgroup will ensure that quality control is maintained and that adequate training and standardization of measures is obtained prior to study related activities commencing. The total time the investigators estimate for completion of behavioral tasks at each study visit is about 1 hour.

Neuroimaging: Eligible participants will undergo neuroimaging at baseline and at 3-month intervals. Neuroimaging includes both functional MRI and structural acquisitions. A brief description of procedures for each of these is outlined below; detailed descriptions will be in the Neuroimaging Procedures Manual. In total, the investigators estimate that approximately 90 minutes will be spent in the scanner per visit. In addition, research personnel will spend about 30 minutes preparing participants. Neuroimaging will be performed at baseline (study entry) and at 3-month intervals, for a total of 10 total neuroimaging sessions for the study duration.

The collection of socio-demographics, lifestyle, clinical and other health-related information obtained through self-report questionnaires and clinician interviews will complement the physical, biological, neuroimaging (including EEG) measurements collected at study visits. The information obtained will form a database that allows a wide range of research questions, both anticipated and unforeseen, to be addressed in the future.

Some questionnaires will be given to participant parents as required for minors. Additional assessments completed with minors will be done with study staff to assist with any questions or difficulty with the assessments.

Note: The schedule of assessments to be completed will vary from time to time within this longitudinal study to help balance the data between age, gender and diagnosis breakdown of our enrolled participants for data analyses. The schedule of assessments will NOT exceed the

  1. Monthly Surveys: 12 times a year
  2. MRI: 4 times a year
  3. EEG: 4 times a year
  4. Biospecimen collection: 4 times a year
  5. Cognitive Behavioral Tasks (e.g. NIH Toolbox / Cogstate / Emoticom)
  6. Extensive Self-report and Clinician rated assessments: 4 times a year
  7. Optional Stool Sample collection: 4 times a year
  8. Optional Dermal Biopsy: 1 time only
  9. Optional M-health: Duration of the study (starting from Baseline)

Condition Depression, Depression, Bipolar
Treatment Observational study
Clinical Study IdentifierNCT02919280
SponsorUniversity of Texas Southwestern Medical Center
Last Modified on13 June 2022


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