Study to Evaluate Potential Predictors of Relapse in Participants With Major Depressive Disorder (MDD)

This is a prospective, multicenter, longitudinal, single-cohort, observational study in
participants with MDD who have responded to, and are continuing to respond to and receive, an
oral antidepressant treatment regimen. The study will consist of 2 parts: a screening phase
of up to 2 weeks, and an observational phase of variable duration.

Inclusion Criteria:

- Participants must have met Diagnostic and Statistical Manual of Mental Disorders-5th
edition (DSM-V) criteria for diagnosis of nonpsychotic MDD within the past 2 years
(that is, the start of the most recent major depressive episode (MDE) must be less
than or equal to 24 Months before screening), as confirmed using the MINI
International Neuropsychiatric Interview (MINI - DSM-V). MDD must be recurrent, rather
than a single episode

- During the most recent MDE, participant must have responded to, and must be continuing
to receive and respond to, an oral antidepressant treatment regimen (given at an
adequate dosage and duration based on the Massachusetts General Hospital
Antidepressant Treatment Response Questionnaire), within the past 3 months. A change
in the oral antidepressant treatment regimen since the time of achieving response in
the most recent episode will be allowed

- Participants must have a Montgomery Asberg Depression Rating Scale total score less
than or equal to 14

- Participant must be willing and able to complete self-reported assessments via a
study-specific smartphone, and must be willing to wear an wrist actigraphy device for
the duration of the study

Exclusion Criteria:

- Participant has any of the following DSM-V psychiatric diagnoses: MDD with psychotic
features (lifetime), bipolar disorder (including lifetime diagnosis), schizophrenia,
or schizoaffective disorder

- Participant has a history of drug or alcohol use, with a severity of at least moderate
or severe, according to DSM-V criteria, within 6 months before screening

- Participant is currently receiving or has received vagal nerve stimulation (VNS),
electroconvulsive therapy (ECT), or transcranial magnetic stimulation (TMS) or deep
brain stimulation (DBS) for the most recent MDE

- Participant is currently receiving stimulants, anticonvulsants, or mood stabilizers
for treatment of his or her MDD

- Participant is a woman who is pregnant, or planning to become pregnant, while enrolled
in this study