In this study, the investigators will perform an exploratory randomized trial of Positive Psychology (PP). The trial will consist of 50 participants and will compare the impact of a phone-based PP intervention vs. an attentional control condition, in Major Depressive Disorder (MDD) patients who are hospitalized for SI or following a suicide attempt. This is a 12 week trial with 6 weeks of intervention and two blinded follow-up assessments at 6 and 12 weeks.

Specific Aim #1: To assess the feasibility and acceptability of the phone-based PP intervention in this high-risk population.

Hypotheses: The intervention will be feasible (with most patients completing at least 4/6 PP and with follow-up data from at least 80% of subjects). The ratings of ease and subjective helpfulness of the exercise and other mental states as measured before and after each PP exercise will be more than 6 out of 10 and higher than the same ratings obtained from subjects in the control condition.

Specific Aim #2: To examine the impact of the six-session PP intervention on positive psychological well-being.

Hypothesis: Compared to control subjects, subjects randomized to PP will have greater scores on scales of optimism (measured via the Life Orientation Test-Revised [LOT-R]), gratitude (Gratitude Questionnaire-6 [GQ-6]), and positive affect (Positive Affect Negative Affect Schedule [PANAS]) at 6 and 12 weeks.

Specific Aim #3 (primary aim): To assess the impact of the PP intervention on key suicide risk factors.

Hypothesis: PP subjects will have greater scores on scales of hopelessness (Beck Hopelessness Scale [BHS]; primary study outcome measure), suicidal ideation (SI) (Concise Health Risk Tracking scale [CHRT]), and depression (Quick Inventory of Depressive Symptomatology-Self Report [QIDS-SR]) at 6 and 12 weeks.

We will also measure impact on readmission and suicide attempts to assess these key outcomes.

Participants will be randomized to receive the intervention or recollection (control) arm. They will be randomized by a random-number generator and will be assigned a condition after receiving baseline questionnaires. The RA/blinded assessor will be blind to the study condition. The interventionist and subjects will not be blind to the study condition.

Baseline assessments: After consent and eligibility rule outs, subjects will receive baseline questionnaires to assess hopelessness (BHS46), suicidality (CHRT47), depression (QIDS-SR48), and positive states (LOT-R,43 GQ-6,44 PANAS45). Then, subjects will be randomized via random number generator to receive the control or intervention condition.

After completing baseline questionnaires and receiving randomization, subjects in both groups will have a 20 minute initial in-hospital session ("week #1"), within a week of anticipated discharge, in which the interventionist will provide a treatment manual specific to their condition, review the rationale for the initial exercise, and assign the exercise. The next day, the exercise will be reviewed and an exercise assigned for the next week. Immediately after completing the exercise, subjects will rate (on a Likert scale of 1-5) ease of exercise completion, overall utility, and initial impact on hopelessness/optimism, to assess immediate effects.

After discharge from the hospital, subjects will have five 20 minute weekly phone sessions ("weeks #2-6") with a different exercise used each week (assigned in the same order to all subjects). The phone sessions will include: (a) review of the prior week's exercise (including subject ratings of ease and impact as in week #1), (b) discussion of the rationale and assignment of the next week's exercise via a guided review of the study manual, and (c) completion of the Clinical Status questions and the Clinical Global Improvement scale (CGI) to monitor symptoms and improvement. Sessions will be audiotaped and random sessions reviewed by our PP consultant to ensure fidelity to the intervention (and that other techniques, e.g., Cognitive Behavioral Therapy, are not used).

Positive psychology (intervention condition)

Exercises. These were selected based on their superior performance in our pre-pilot study and others' work:

• Gratitude for positive events: Subjects recall three events, small or large, in the preceding week that were associated with satisfaction, happiness, pride, or other positive states.
• Gratitude letter: Subjects write a letter of gratitude thanking a person for an act of kindness; subject may, at their discretion, share the letter with the other person.
• Performing acts of kindness: Subjects are instructed to complete three acts of kindness in one day. The acts can be small or large, planned or spontaneous, but must be expressly completed to be kind to another.
• Using personal strengths: Subjects undergo a brief assessment of personal strengths, then find a new way to use that strength in the next 24 hours.
• Enjoyable and meaningful activities: Subjects complete a series of self-selected activities that vary between those that bring immediate boosts in mood and those that are more deeply meaningful.
• Repetition of an exercise previously done.

Recollection (control condition) The recollection condition was selected because it has been used in a prior study by our team of a phone-based positive psychology intervention and it was found to be feasible and well-accepted. Each week, subjects will record recent life events in a manual without describing emotions associated with the events. The nature, setting, or type of events to be recorded will differ each week to provide variety and maintain subjects' interest. This will be described as an intervention that may assist with organization and hone recall of important life events. Also, as an attentional control, it has a parallel structure to the experimental arm with a treatment manual, weekly exercises, and weekly calls to review exercises.

Follow-up 6 and 12 week phone call. After completion of the intervention (6 weeks), and then at 12 weeks, a blinded study research assistant (RA) will call subjects at 6 and 12 weeks to repeat measures of hopelessness (BHS), suicidality (CHRT), depression (QIDS-SR) and positive states (e.g., GQ-6, PANAS, LOT-R). Subjects will also be asked to rate their overall satisfaction with the treatment they received for their cardiac condition (outside of this study) over the last 6 and 12 weeks on a scale of 1 (excellent) to 5 (poor). We will record specific times that subjects would prefer to be called (and not to be called) for future follow-ups, to reduce intrusion on subjects' lives. We will also send a postcard to subjects reminding them of their upcoming study phone call. The blinded assessor will make 2 follow-up phone calls (at 6 and 12 weeks) to gather information about outcomes. If subjects would rather complete the questions in written form rather than over the phone, we will send them a written packet at the time of each follow-up.

Inclusion Criteria:

• Patient admitted to Massachusetts General Hospital inpatient psychiatric unit
• Age 18 and older
• Able to read/write in English
• SI documented on admission OR admission due to a suicide attempt
• Admission diagnosis of MDD (and current major depressive episode), confirmed using the Mini International Neuropsychiatric Interview (MINI) and inpatient chart review

Exclusion Criteria:

• Psychotic symptoms, as assessed using the MINI and inpatient chart review
• Cognitive disorder, assessed using a six-item cognitive screen developed for research
• Primary admission diagnosis of substance use disorder