Cannabidiol Oil for Treatment-Resistant Major Depression

Major depressive disorder (MDD) is a highly prevalent psychiatric condition and one of the leading causes of disability worldwide. Despite the availability of several antidepressant treatments, approximately one-third of patients do not achieve adequate symptom remission after multiple treatment attempts, characterizing treatment-resistant depression. This condition is associated with substantial functional impairment, reduced quality of life, increased healthcare utilization, and elevated suicide risk. The endocannabinoid system has emerged as a promising target for the treatment of mood disorders because of its involvement in emotional regulation, stress response, neuroplasticity, neuroinflammation, and neurotransmitter modulation. Cannabidiol (CBD), a non-intoxicating phytocannabinoid derived from Cannabis sativa, has demonstrated anxiolytic, anti-inflammatory, neuroprotective, and antidepressant-like effects in preclinical studies, while preliminary clinical evidence suggests potential benefits in psychiatric disorders. The ANANDA trial is a multicenter, randomized, double-blind, placebo-controlled, parallel-group clinical trial designed to evaluate the efficacy, safety, and tolerability of full-spectrum cannabidiol oil as adjunctive therapy in adults with treatment-resistant major depressive disorder. The study will be conducted at the University of Southern Santa Catarina (UNISUL) and the Federal University for Latin American Integration (UNILA). A total of 120 participants diagnosed with treatment-resistant major depressive disorder will be randomized in a 1:1 ratio to receive either full-spectrum cannabidiol oil or placebo for 12 weeks while maintaining stable antidepressant treatment. Randomization will be performed using a computer-generated allocation sequence. Participants, investigators, healthcare providers, outcome assessors, and members of the research team responsible for participant follow-up and data analysis will remain blinded to treatment allocation throughout the study period. The placebo formulation will be matched to the active intervention in appearance, color, packaging, and administration conditions to maintain blinding. Clinical evaluations will be performed at baseline, Week 4, and Week 12 using validated instruments for depressive symptoms, anxiety, sleep quality, perceived stress, adverse effects, and quality of life. Biological samples will be collected at baseline and after 12 weeks of treatment to assess inflammatory and neuroendocrine biomarkers potentially associated with treatment response. The primary outcome is the change in depressive symptom severity measured by the Montgomery-Åsberg Depression Rating Scale after 12 weeks of treatment. Secondary outcomes include changes in anxiety symptoms, sleep quality, perceived stress, biological markers, safety, and treatment tolerability. The results of this study may contribute to a better understanding of the therapeutic potential of cannabidiol in treatment-resistant depression and may provide evidence to support future clinical applications of cannabinoid-based interventions in psychiatry.