What is the recommended initial diagnostic study for a patient presenting with symptoms of depression?

The recommended initial diagnostic study for a patient presenting with symptoms of depression is Thyroid Stimulating Hormone (TSH). This is because hypothyroidism can present with depressive symptoms, and checking TSH levels is a crucial step to rule out thyroid dysfunction as a contributing factor to the patient's mood symptoms. A normal TSH level suggests that the depression is likely not due to a thyroid problem, allowing healthcare providers to focus on other potential causes or treatments for the depressive symptoms.

While other tests like a Complete Blood Count (CBC), Magnetic Resonance Imaging (MRI), and Basic Metabolic Panel (BMP) may provide valuable information in different contexts, they are not typically the first line of assessment for depression. A CBC might help rule out anemia or infection, an MRI is usually reserved for cases with neurological concerns, and a BMP assesses electrolyte levels but does not directly address potential metabolic conditions linked to mood. Therefore, TSH testing is uniquely positioned as a relevant and specific initial diagnostic measure in the evaluation of depression.