Can a Low-Dose Add-On drug lift depression and boost thinking in bipolar disorder?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Patient Inclusion Criteria: * Age: 18-75 * Male or female * Bipolar Disorder type I or type II * Current treatment-resistant depressive episode (with MADRS \>/= 24 and item 2 (reported sadness) \>/= 3) for a minimum of 2 weeks but \</= 52 weeks at screening visit and baseline visit * Patients must have failed at least one other treatment for the current depressive episode * If female and of childbearing potential, is using an adequate method of contraception. Adequate methods of contraception include abstinence; oral contraceptive pill or surgically implanted device; intra-uterine device; condom plus spermicidal foam or jelly; or tubal ligation * Is treated with a mood stabilizer (lithium and/or valproate and/or lamotrigine and/or quetiapine \</= 100mg/day) * The following laboratory values are within normal limits at Screening: CBC with differential; ferritin; extended electrolytes (sodium, potassium, chloride, calcium, magnesium, phosphate); thyroid function test(s); kidney function tests; hemoglobin A1c; lipid profile; prolactin * Normal EKG at Screening * Patient is able to give his(her) consent Patient Exclusion Criteria: * Is at high risk of suicide as defined by a score of \>/= 3 to item 10 of MADRS and/or in the clinical opinion of the investigator * Hypo(mania) episode with YMRS \>/= 8 * Psychotic symptoms as defined by a score of \>/= 4 to item 8 (content) of YMRS and/or in the opinion of the investigator * Is treated with fluoxetine OR carbamazepine * Is treated with risperidone OR olanzapine OR quetiapine \> 100mg/day OR ziprazidone OR any other antipsychotic * Is pregnant or lactating or absence of contraceptive treatment * Drug abuse or dependence as per DSM-V (MINI) * Unstable medical condition * Other unstable and/or untreated psychiatric condition, organic brain disorder, unstable and/or untreated medical condition such as hypothyroidism, hyperthyroidism, diabetes, cardiac condition, hypertension * Deficit in vitamin B12 or folate * Rapid cycling (more than 4 mood episodes per year) * Active or history of difficulty to swallow * Seizures not currently controlled with medications * Orthostatic hypotension defined as a drop in systolic blood pressure of at least 20 mmHg or of diastolic BP of at least 10 mmHg within 3 minutes of standing * A history of clinically significant cardiovascular disorders and cardiac arrhythmias * A low white blood cell count * Known eye disease * Involuntary, irregular muscle movements, especially in the face * Known hypersensitivity to Brexpiprazole and any components of its formulation * Known lactose intolerance or have hereditary galactose intolerance or glucose-galactose malabsorption, because Brexpiprazole and placebo tablets contain lactose (a disaccharide of glucose and galactose) * Active inflammatory disease including lupus, colitis, Crohn's disease, psoriasis, irritable bowel syndrome (IBS) * Mild or major neurocognitive disorder * Previous history of sensitivity/low tolerance to medications metabolized by CYP 2D6 inhibitors, or CYP 3A4 inducers Control Inclusion Criteria: * Age: 18-75 * Male or female * No current or past history of any psychiatric disorder * Patients must have failed at least one other treatment for the current depressive episode * If female and of childbearing potential, is using an adequate method of contraception. Adequate methods of contraception include abstinence; oral contraceptive pill or surgically implanted device; intra-uterine device; condom plus spermicidal foam or jelly; or tubal ligation * The following laboratory values are within normal limits at Screening: CBC with differential; ferritin; extended electrolytes (sodium, potassium, chloride, calcium, magnesium, phosphate); thyroid function test(s); kidney function tests; hemoglobin A1c; lipid profile; prolactin * Normal EKG at Screening * Patient is able to give his(her) consent Control Exclusion Criteria: * Alcohol or drug abuse * Deficit in vitamin B12 or folate * Seizures not currently controlled with medications * History of clinically significant cardiovascular disorders and cardiac arrhythmias * Mild or major neurocognitive disorder Patient/Control Exclusion Criteria for MRI: * Pacemaker * Heart/vascular clip * Metal prosthesis * Metal fragments in body * Transdermal patch * Aneurysm clip * Prosthetic valve * Claustrophobia * Pregnant