Participants will listen to lessons from the Healthy Minds Program at home for four weeks, which will not include any actual meditation exercises.

On two nights each week during the four weeks of the intervention, participants will sleep in the lab and undergo sham TES-TI stimulation for approximately 10 hours per night

Participants will sleep in the lab and undergo active TES-TI stimulation for approximately 10 hours per night.

Imaging protocol will include: structural T1-weighted and T2-weighted images, resting-state functional MRI, task-based functional MRI, and multi-shell diffusion weighted MRI, total scan time will be approximately 2 hours

This is a 10-item inventory asking participants to rate from 0 (never) to 4 (very often) the frequency with which they have felt various kinds of stress in the last month. Scores range from 0 to 40 with higher score indicative of higher stress.

This is a 24-item inventory asking participants to rate from 1 (strongly disagree) to 7 (strongly agree). Scores range from 24 - 168, higher scores are indicative of less Healthy Emotionality

The CFI is a 20-item self-report measure to monitor how often individuals engage in cognitive behavioral thought challenging interventions. Participants rate each item from 1 (strongly disagree) to 7 (strongly agree). Scores range from 13 - 91, higher scores are indicative of increased ability to perceive multiple alternative explanations.

The CFI is a 20-item self-report measure to monitor how often individuals engage in cognitive behavioral thought challenging interventions. Participants rate each item from 1 (strongly disagree) to 7 (strongly agree). Scores range from 7 - 49, higher scores are indicative of increased ability to perceive difficult situations as controllable.

The DERS-18 is a 18-item self-report measure which assesses various aspects of emotion regulation, including emotional awareness, acceptance of emotional responses, impulse control, and effective goal-directed behavior during emotional experiences using a 5-point scale from 1 (almost never) to 5 (almost always). Higher scores suggest greater problems with emotion regulation.

This validated assessment tool asks participants to rate 8 items that measure sleep-related difficulties using a 5-point Likert scale. Scores range from 8 to 40 with higher scores indicative of more sleep disturbance.

This 20-item self-report questionnaire is a widely used self-report questionnaire which assesses symptoms of post-traumatic stress disorder (PTSD). Participants rate from 0 (not at all) to 4 (extremely) the severity of their symptoms. Scores range from 0 to 80 with higher scores indicative of more severe PTSD symptoms.

This 5-item scale is a global measure of Well-Being, where higher scores reflect greater overall wellbeing (range 0-25).

This validated assessment measuring subjective perceptions of the restorative or inadequate properties of sleep will be given the morning after every sleep lab visit. The questionnaire includes 9 items rated on a 5 point scale given at the time of awakening. Scores range from 0 to100, where higher scores are indicative of better restorative sleep.

Participants will be asked to rate the depth of their prior night's sleep using 5-point Likert-type scale. How deep was your sleep? from 1 (light) to 5 (deep) after every sleep laboratory visit.

This validated questionnaire evaluates subjective sleep quality. Each of the questionnaire's 19 self-reported items belongs to one of seven subcategories: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication, and daytime dysfunction. Five additional questions rated by the respondent's roommate or bed partner are included for clinical purposes and are not scored. Each component is scored 0 (no difficulty) to 3 (severe difficulty), scores ranging from 0 to 21. Higher scores are indicative of worse sleep quality.

This battery assesses known suicide risk factors. The 13 items ask participants about their sociodemographic characteristics; past experiences with mental health symptoms; thoughts of self-harm, and self-harming actions; psychological traits. Scores range from < 0.39408955691660219 to >= 0.67215170692043313 with higher scores indicative of increased suicidality.

This self-report measure assesses the suicide belief system. Using a 5-point likert scale, participants rate 6 items measuring their enduring or identity-based hopelessness rooted in their beliefs about being undesirable, their emotional state as intolerable, and life challenges as insurmountable. Scores range from 6 to 30 where higher scores are indicative of increased suicidality.

This 17-item validated tool assesses participants' passive and active suicidal ideation in the past seven days using a six-point Likert scale, from 0 (Not in the past 7 days) to 5 (several times every day). Higher score reflects greater suicidal ideation.

The NIH Toolbox Loneliness consists of 5 self-report items assessing participants' feelings of loneliness and social isolation on a 5-point Likert scale ranging from 1-5 where higher scores indicate increased loneliness.

The FFMQ is a widely used self-report inventory that assesses mindfulness across five facets: observing, describing, acting with awareness, non-judging of inner experience, and non-reactivity to inner experience. Participants rate their agreement level with 39 items using a 5-point Likert scale. Scores range from 39 to 195 with higher scores indicative of increased mindfulness.

This self-report measure evaluates the ability to create a mental separation or distance from one's internal experiences by asking participants to rate 10 items assessing defusion across a spectrum of internal thoughts and emotions on a 6-point scale, ranging from 0-5. Total scores range from 0 to 50 with higher scores indicative of increased defusion.

This is a 37-item inventory asks participants to rate their sense of life with purpose and perceived reasons for living using a 5-point Likert scale. The current study will administer the computer adaptive test (CAT) version of the instrument, in which subsequent item choice of the system will be based on participants' previous responses. Scores range from 37 to 185 with higher scores indicative of higher feelings of meaning and purpose.

The inventory consists of 6 items which measures the quality of the therapeutic alliance between a user and a digital mental health intervention, which is the HMP in this study. Participants rate their experience using the HMP on a 7-point scale, ranging from 1 (strongly disagree) to 7 (strongly agree). Scores range from 6 to 42 where higher scores indicate better user experience with the app.

The PTQ is a self-report instrument assessing repetitive and uncontrolled thinking by asking participants to rate 15 items about the frequency, duration, and perceived uncontrollability of repetitive thoughts on a scale of 0-4. Scores range from 0 to 60. The higher the score, the higher the level of perseverative thinking or repetitive thoughts experienced by the individual.

This subscale is an 11-item scale of decentering originally developed to assess mechanisms of Mindfulness Based Cognitive Therapy (e.g., "I can separate myself from my thoughts and feelings."). The EQ-D is originally scored on a 5-point Likert scale (1 = never to 5 = all the time) where higher scores indicate increased decentering.

The experience sampling method assesses present moment experience using a short series of questions administered on a smart phone 6 times a day for 7 days. Questions measure current emotional and cognitive state. Score range from 1-5 where higher scores indicate increased emotional state

This task involves participants viewing words on a screen. Words are either related to self (e.g., "I"), others (e.g., "They"), life (e.g., "survive") or death (e.g., "die"). Like other Implicit Association Tests, participants are asked to indicate which category each word belongs to. Across the trials, self and other are paired with either life or death. The measure can be scored as an implicit marker of how easily participants associated death with themselves. Scores are greater than 2 or less than 2, with more positive values indicating a stronger association between self and death.

This task involves participants viewing and choosing between two abstract visual stimuli (i.e., geometric shapes). After each choice they receive feedback that is either positive (+10) or negative (-10) feedback devoid of monetary value. Stimulus-outcome pairings are reversed over the course of the experiment.

This task involves viewing a series of numbers and letters. Participants are asked to indicate using a button press which number was different from the other numbers. Scores are reported as percentage correct.

This task involves viewing a series of faces and words. Participants are asked to identify the emotional expression of the faces. Percent change in reaction time is reported.

This task involves viewing a series of faces and words. Participants are asked to identify the emotional expression of the faces. Percent correct is reported.

This is a mobile measure of attention, based on the Sustained Attention to Response Task (SART), a validated, standardized laboratory task. This task lasts five minutes and measures attention regulation and sustained attention, as assessed based on reaction time, reaction time variability, and accuracy.

This is a mobile measure of attention, based on the Sustained Attention to Response Task (SART), a validated, standardized laboratory task. This task lasts five minutes and measures attention regulation and sustained attention, as assessed based on reaction time, reaction time variability, and accuracy.

This is a mobile measure of attention, based on the Sustained Attention to Response Task (SART), a validated, standardized laboratory task. This task lasts five minutes and measures attention regulation and sustained attention, as assessed based on reaction time, reaction time variability, and accuracy.

This task involves viewing pictures categorized as neutral, positive, or negative. Participants may be asked to press a button indicating the valence category of the picture. Positive and negative affect ratings will be made on a continuous sliding scale ranging from 0 to 6.

This task involves viewing a series of letters and numbers. Participants are asked to determine whether a target letter was a certain letter (e.g., "T"). Participants receive feedback on their choices. The feedback is not always accurate and participants are informed of this. Change range is from 0 to 1.

This task involves viewing a series of letters and numbers. Participants are asked to determine whether a target letter was a certain letter (e.g., "T"). Participants receive feedback on their choices. The feedback is not always accurate and participants are informed of this. Accuracy is from 0 to 1.

This task involves viewing a series of letters and numbers. Participants are asked to determine whether a target letter was a certain letter (e.g., "T"). Participants receive feedback on their choices. The feedback is not always accurate and participants are informed of this. Response time is reported.

Psychomotor vigilance performance will be measured with the visual psychomotor vigilance task (PVT) a portable, easily usable reaction-time test with a that can yield rapid and reliable assessments of psychomotor vigilance impairment. Participants will take a 3 minute version of the PVT on a tablet or laptop every morning after an in-laboratory sleep visit to assess alertness. Reaction time is reported.

Resting-state fMRI connectivity will be assessed based on the Fisher-Z transformed (FZT) correlation of each seed region with all other voxels in the brain. In order to test for intervention effects, difference maps will be computed and a voxelwise analysis of the difference maps across the whole brain will be used to identify regions that might differ in connectivity between groups over time. A z-score is the number of standard deviations away from the mean.