Pathobiology of Depression

Depression is an extremely common psychiatric disorder, affecting over 280 million individuals worldwide. It causes significant impairments in both emotional and physical health, leading to persistent mood disturbances, cognitive impairments, and somatic symptoms. Depression results from intricate interactions among social, psychological, and biological factors. Recent studies have identified key roles of oxidative stress and inflammation in this disorder. TNF-α and IL-1β, proinflammatory cytokines released in response to stress, initiate neuroinflammation by activating microglia. Alongside increased inflammatory processes, oxidative stress further exacerbates these mechanisms. Key mechanisms include alterations in neurotransmitter systems, particularly serotonin and norepinephrine, which are core contributors to depressive symptoms. Inflammation-driven mechanisms, such as activation of the kynurenine pathway, produce neurotoxic effects that worsen depressive symptoms. Therefore, treatment for depression should be integrative, incorporating pharmacological, lifestyle, and psychosocial interventions. Exercise and anti-inflammatory therapies are promising approaches for enhancing treatment outcomes, especially for treatment-resistant forms of depression. Understanding the mechanisms underlying depression is crucial for developing novel therapeutic strategies that could significantly reduce its global burden.