Could an antibiotic ease depression in people with obesity?

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

Inclusion Criteria: * Sufficient communication skills to understand the intervention and complete the assessments. * Able to give informed consent. * Treatment resistant depressed (i.e., non-responders to current antidepressant treatment, for at least 6-weeks AND at least one other previous antidepressant). * Tolerant to the current antidepressant. * Able to undergo 2 MRI scans. * Accepting augmentation with minocycline. * CRP \>3mg/L at screening. * No plans to change current therapy for the duration of participation. Exclusion Criteria: * Active suicidal ideation. * Current primary diagnosis of psychotic disorder, bipolar disorder, obsessive-compulsive disorder, or post-traumatic stress disorder. * Have an acute infection or an autoimmune disorder, because of both the rare but described association between minocycline and systemic lupus erythematosus, and the potential confounder effects of these conditions on immune biomarkers. * Alcohol misuse disorder or drug addiction. * Neurological disorders (Parkinson's, Alzheimer's). * Current serious cardiovascular problems. * Have acne or psoriasis. * Currently taking any antibiotic, immunosuppressive medication, or warfarin. * Taken any tetracycline within the last month. * Currently taking Lithium or retinoids (Acitretin, Alitretinoin, Isotretinoin). * Refuse that we contact their GP to inform them about their participation. * \[OPTIONAL - if not met, cannot undergo the MRI\] Has any metal implants in their body such as pacemakers, dental fillings, IUD device (if applicable), or had any accidents where metal fragments might have entered the body or eye. * Pregnant or breastfeeding * Have a positive pregnancy test before starting the study/are unwilling to take a pregnancy test and are unwilling to agree to use an acceptable form of contraceptive throughout the study period (e.g., condoms, intrauterine device (IUD)/intrauterine system (IUS), injection, patch, ring). Female participants who use combined oral contraceptives as their main form of birth control will need to use an additional barrier method for the duration of treatment and for 7 days following completion of treatment. * Are currently participating in another Clinical Trial of Investigational Medicinal Product (CTIMP).