The investigators are doing this study to see if "positive psychology" can help adults with depression or bipolar disorder.

Positive psychology involves exercises-short tasks-that try to increase good feelings and emotions, like optimism, happiness, personal strengths, and well-being. Positive psychology exercises might include imagining a bright future, being grateful for good events, forgiving others, and doing kind acts for others.

The investigators want to see if practicing positive psychology exercises after leaving the hospital can increase feelings of hope, optimism, and positive thinking. The investigators are asking you to take part in this research study because you are in the hospital for depression or bipolar disorder.

This research study will compare "positive psychology exercises" to "control condition exercises." During the study, you may take part in control condition exercises instead of positive psychology exercises.

Inclusion Criteria:

• Patient admitted to Massachusetts General Hospital Inpatient Psychiatric Unit
• Age 18 and older
• Able to read and write in English
• Admission diagnosis of major depressive disorder or bipolar affective disorder (current depressive episode), confirmed using the Mini International Neuropsychiatric Interview and inpatient chart review

Exclusion Criteria:

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