Sorry, the best answer is C. A PHQ-9 score of 21 indicates severe depressive symptoms, thus both psychotherapy (i.e., CBT, interpersonal therapy, or behavioral activation) and pharmacotherapy are recommended in combinations A is incorrect because, although CBT is a recommended therapeutic intervention, the severity of depressive symptoms would be best treated in combination with medication. B is incorrect with similar rationale to why A is incorrect (i.e., combination of both psychotherapy and medication). D is incorrect because antipsychotics are best utilized as augmentation agents to antidepressants when partially responsive to monotherapy.
Reference: Lam RW, Kennedy SH, Adams C, et al. Canadian Network for Mood and Anxiety Treatments (CANMAT) 2023 update on clinical guidelines for management of major depressive disorder in adults. Can J Psychiatry. 2024;69(9): 641-87. Doi: 10.1177_07067437241245384.