Metformin as Adjunct Therapy in Depression-obesity Comorbidity: Clinical and Genetic Evaluation

INCLUSION CRITERIA Group I: Normal Controls Group II: Depression Group III: Obesity Group IV and V: * Age ≥ 18 years * Both males and females * Recurrent depressive disorder (6A71) according to ICD-11, * Asian cut off: Obese and overweight (BMI \< 23) * BDI score ≥ 13 or PHQ score ≥ 4 * Either medication-naïve or medication-free for at least 2 weeks before enrollment, or the patient did not take antidepressants during the last 7 days before study entry (discontinuation of effective medication to enable study participation is prohibited) * In case of non-psychotropic medication: The patient received stable pharmacological medication for at least 14 days before study entry (any changes in medication dose or frequency of therapy must be answered with no) EXCLUSION CRITERIA Groups I-III: Negative Controls (Normal: no depression and Obesity for SNP comparison only) * Age less than 18 * Dementia/ Mentally impaired who can not fill self report performas for inclusion criteria Group IV: Positive Control (RCT patients) * Patients with comorbid conditions (HTN, CKD) if taking any drug for that condition. * The patient is not an employee of the investigator study site, or a family member of the employees or the investigator, or otherwise dependent on the sponsor, the investigator, or the investigator study site. * The patient did not participate in other interventional trials during the 6 months before and at the time of this trial. The patient does not have a history of non-response to antidepressants included in the study. * The patient has not given birth within the 6 months before study entry and is not breastfeeding * The patient did not receive treatment with ketamine, irreversible MAO inhibitor (e.g. tranylcypromine), electroconvulsive therapy (ECT) or other stimulatory treatments in the index episode. * The patient is not diagnosed with dementia and does not have moderate or severe impairment of general cognitive function according to clinical impression. * The patient does not meet the criteria for alcohol use disorder (DSM-5: 303.90; ICD-10: F10.20) or substance use disorder (DSM-5: 304; ICD-10: F11.20 - F19.20) in DSM-5, and a urine/serum drug screening is negative (except for benzodiazepines and opiates). * The patient does not have: * A known allergy or contraindication against antidepressants included in the study * History of suicidal tendencies * Uncontrolled hepatic disorder, renal or cardiovascular disease * DM * Untreated hypothyroidism * History of myocardial infarction or stroke * Symptomatic peripheral arterial disease * Monogenic familial hypercholesterolemia