An exploratory study to biotype adult patients with unipolar depression using digital technologies.

Patients:
1. Written informed consent must be obtained before any assessment is performed.
2. Males and females, age 18 to 65 years (inclusive).
3. Body mass index (BMI) between 18 and 32 kg/m2.
4. Primary diagnosis of moderate to severe major depressive disorder (MDD) without psychotic features or persistent depressive disorder (PDD)/dysthymia according to the DSM-IV or DSM-5, as diagnosed by the attending general practitioner, psychiatrist or clinical psychologist and confirmed with the Mini International Neuropsychiatric Interview (MINI) version 7.0.
5. Total MADRS-SIGMA score of >22 at Screening.
6. Meeting one of the following conditions;
o no treatment with antidepressant drugs (SSRI, SNRI, mirtazapine, TCA, MAO-I) and/or lithium for at least 2 weeks (6 weeks for fluoxetine) before Screening; or
o treatment with antidepressant drugs (SSRI, SNRI, mirtazapine, TCA, MAO-I), with or without lithium, at a stable dose for at least 4 weeks prior to Screening (6 weeks for fluoxetine)
7. Must read and speak Dutch as a first or second language.
8. Able to comply with the study procedures, prohibitions and restrictions (drug and alcohol use) as specified in the protocol.
9. Android-based smartphone with Android version 5.0 or higher.

Healthy volunteers:
1. Written informed consent must be obtained before any assessment is performed.
2. Male or female subjects, 18 to 65 years (inclusive).
3. Body mass index (BMI) between 18 and 32 kg/m2.
4. Must read and speak Dutch as a first or second language.
5. Able to comply with the study procedures, prohibitions and restrictions (drug and alcohol use) as specified in the protocol.
6. Android-based smartphone with Android version 5.0 or higher.

Patients:
1. Current or previously diagnosed psychotic disorder, bipolar disorder, mental retardation, cluster B personality disorder (i.e. borderline, antisocial, narcissistic or histrionic personality disorders).
2. Clinically significant suicidality within the past 6 months as demonstrated with the C-SSRS or as judged by the investigator.
3. Use of sedative medication started within 2 weeks before Visit 1 and/or daily use of benzodiazepines with a dose equivalent of more than 10 mg Diazepam.
4. Foreseeable alterations in the dose of antidepressant drugs (SSRI, SNRI, mirtazapine, TCA, MAO-I) or lithium during the course of the study.
5. Positive alcohol breath test or urine test for drugs of abuse at Screening (positive urine test for benzodiazepines is allowed) or a current diagnosis of substance use disorder (including alcohol but excluding nicotine), or previous substance use disorder (including alcohol but excluding nicotine) within the past 12 months according to DSM-IV or DSM-5.
6. Evidence of any active or chronic disease or condition that could interfere with the conduct of the study.
7. Positive urine β-human chorionic gonadotropin (β-hCG) pregnancy test at Screening in women of childbearing potential.
8. Wearing a pacemaker or other internal medical device (e.g. Vagus nerve stimulation (VNS), Deep Brain Stimulation (DBS)).
9. Current enrollment in another study.

Healthy volunteers:
1. Current or previous clinically relevant history or family history of psychiatric disorders, neurological disorders or neurosurgery.
2. Positive alcohol breath test or urine test for drugs of abuse at Screening or a current diagnosis of substance use disorder (including alcohol but excluding nicotine) or previous substance use disorder (including alcohol but excluding nicotine) within the past 12 months according to DSM-IV or DSM-5.
3. Evidence of any active or chronic disease or condition that could interfere with the conduct of the study.
4. Clinically significant abnormalities, as judged by the investigator, in laboratory test results (including hepatic and renal panels, complete blood count, chemistry panel and urinalysis).
In the case of uncertain or questionable results, tests performed during Screening may be repeated before inclusion to confirm eligibility or judged to be clinically irrelevant for healthy subjects.
5. Use of any medications (prescription or over-the-counter [OTC]), within 14 days of Visit 1, or less than 5 half-lives (whichever is longer). An exception is paracetamol (up to 2 g/day).
Other exceptions will only be made if the rationale is clearly documented by the investigator.
6. Positive urine β-human chorionic gonadotropin (β-hCG) pregnancy test at Screening in women of childbearing potential.
7. Wearing a pacemaker or other internal medical device (e.g. Vagus Nerve Stimulation (VNS), Deep Brain Stimulation (DBS)).
8. Current enrollment in another study.