This thesis explores the cognitive theory of depression and also compares the efficacy of psychotherapy (Cognitive Behavioural Therapy) and pharmacotherapy in treating Major Depressive Disorder (MDD). It provides a theoretical foundation based on Aaron T. Beck’s model and includes neurobiological evidence to support a strong understanding of depression. The work critically analyses current treatment options and emphasizes the superior outcomes of combined therapy. This is especially in moderate to severe or chronic cases. Limitations of each modality are discussed alongside emerging solutions such as digital CBT, augmentation strategies, and collaborative care. The thesis is well-researched, clinically relevant, and highlights the importance of individualized, integrative treatment planning.