diathesis-stress model can work in tandem with the biopsychosocial model. The biopsychosocial model is a holistic approachmental illness which considers factor in isolation but proposes a multi-pronged approach to the treatment of such disorders. This essay will the terms diathesis-stress model Major depressive disorder; discuss the merits and disadvantages of the model; explore theory framework used to explain unipolar depression and analyse how effectively the theory accounts for MDD. The Diagnostic