A Lethargic Client Is Diagnosed with Major Depressive Disorder

A lethargic client is diagnosed with major depressive disorder. After taking antidepressant therapy for 6 weeks, the symptoms have not resolved. Which nutritional deficiency should a nurse identify as potentially contributing to the client's symptoms?

A) Vitamin A deficiency
B) Vitamin C deficiency
C) Iron deficiency
D) Folic acid deficiency