Clinically reviewed by Brandi Richardson, APRN, Nurse Practitioner at Stay Healthy! LLC, Tallahassee, FL.
Clinical Disclaimer: This article is for educational purposes only and does not constitute medical advice. If you are experiencing symptoms of depression or low mood, please consult a qualified healthcare provider. If you or someone you know is in crisis, call or text 988 (Suicide & Crisis Lifeline), available 24/7.
Understanding the medical causes of depression is an important first step in building an accurate diagnosis. Depression is one of the most commonly diagnosed mental health conditions in the United States, but not every case of low mood, fatigue, or cognitive slowing is caused by a primary psychiatric disorder. A number of medical conditions — including thyroid disease, vitamin deficiencies, anemia, and sleep disorders — can produce symptoms that closely resemble clinical depression. At Stay Healthy Med in Tallahassee, FL, Brandi Richardson, APRN, conducts comprehensive evaluations that address both the psychiatric and medical dimensions of mood disorders, helping patients identify the most accurate diagnosis and the most effective treatment path.
Why Medical Evaluation Is Part of a Depression Workup
When a patient reports persistent low mood, fatigue, loss of interest, or difficulty concentrating, the clinical evaluation does not begin and end with a symptom checklist. According to the National Institute of Mental Health (NIMH), depression is diagnosed using clinical criteria — but a thorough evaluation also considers whether an underlying medical condition may be contributing to or producing those symptoms.
Depression Is a Clinical Diagnosis — Not a Lab Test Result
There is currently no single blood test or brain scan that can diagnose depression. The diagnosis is made through a comprehensive clinical interview, validated screening tools such as the PHQ-9, and careful review of a patient’s symptom pattern, personal history, and medical background.
However, because several physical health conditions produce symptoms that are nearly identical to depressive symptoms — fatigue, low mood, cognitive fog, weight changes, and sleep disruption — a responsible clinical evaluation includes ruling out these medical possibilities first or alongside the psychiatric assessment.
When Physical Health and Mood Overlap
The relationship between physical health and mental health is bidirectional. A medical condition can trigger mood symptoms. Depression can also worsen the course of many medical conditions. In some patients, both are present simultaneously. This is why a provider who can evaluate both systems — as is the case at Stay Healthy Med, where primary care and psychiatric care are integrated under one roof — offers a clinical advantage that fragmented care cannot replicate.
Medical Conditions That Can Produce Depression-Like Symptoms
The following conditions are among the most clinically recognized medical causes of depression-like symptoms. Whether any of these applies to a specific patient is a determination that must be made by a qualified healthcare provider based on individual history and presentation.
Thyroid Disorders — Hypothyroidism and Depression
Hypothyroidism — an underactive thyroid gland — is one of the most frequently identified medical mimics of depression. When thyroid hormone levels are insufficient, patients often experience:
- Persistent fatigue and low energy
- Depressed mood and emotional blunting
- Weight gain and cold intolerance
- Slowed thinking and memory difficulties
- Sleep disturbances
These symptoms overlap substantially with Major Depressive Disorder (MDD). A TSH (thyroid-stimulating hormone) blood test is the standard first-line screening for thyroid dysfunction. When hypothyroidism is identified and treated with thyroid hormone replacement, some mood symptoms may improve, although additional treatment for depression may still be appropriate depending on the individual’s symptoms and clinical evaluation.
Iron Deficiency Anemia and Low Mood
Iron deficiency anemia reduces the amount of oxygen delivered to tissues — including brain tissue. Symptoms include:
- Profound fatigue and weakness
- Difficulty concentrating and brain fog
- Irritability and low mood
- Shortness of breath and dizziness
These symptoms are frequently mistaken for depression, particularly in women of reproductive age. A complete blood count (CBC) with serum ferritin is used to evaluate iron stores.
Vitamin D Deficiency and Depressive Symptoms
Vitamin D receptors are present throughout the brain, including in areas that regulate mood. Research has identified an association between low vitamin D levels and depressive symptoms, including:
- Low mood and anhedonia (loss of pleasure)
- Fatigue and decreased motivation
- Cognitive slowing
Vitamin D deficiency is highly prevalent, particularly in individuals with limited sun exposure, darker skin tones, obesity, or restricted diets. Testing involves a 25-hydroxyvitamin D blood level.
Vitamin B12 and Folate Deficiency
Vitamin B12 and folate are essential for neurological function and the synthesis of neurotransmitters — including serotonin and dopamine — that regulate mood. Deficiency in either can produce:
- Depression and mood dysregulation
- Fatigue and weakness
- Memory impairment and cognitive slowing
B12 deficiency is particularly common in older adults, vegans, and long-term users of proton pump inhibitors (PPIs) or metformin. Blood tests for serum B12 and red blood cell folate identify these deficiencies.
Obstructive Sleep Apnea and Fatigue-Driven Low Mood
Obstructive sleep apnea (OSA) causes repeated interruptions in breathing during sleep, leading to fragmented, non-restorative sleep. Patients with untreated OSA commonly present with:
- Excessive daytime fatigue
- Low motivation and flat mood
- Difficulty concentrating
- Irritability
These symptoms are frequently attributed to depression before OSA is identified. Effective CPAP therapy often produces significant improvement in mood and energy.
Diabetes and Mood Dysregulation
Both Type 1 and Type 2 diabetes are associated with higher rates of depression. The physiological effects of chronic hyperglycemia on brain function, combined with the psychological burden of disease management, can contribute to depressive symptoms. Fasting glucose and HbA1c testing identify undiagnosed or poorly controlled diabetes.
Chronic Pain Conditions and Secondary Depression
Chronic pain conditions — including fibromyalgia, arthritis, migraines, and back pain — are strongly associated with secondary depression. Persistent pain alters neurotransmitter function, disrupts sleep, and limits daily functioning, all of which contribute to depressive symptoms.
Adrenal and Cortisol Dysregulation
Conditions affecting cortisol production — including Cushing’s syndrome (excess cortisol) and adrenal insufficiency (insufficient cortisol) — can produce significant mood symptoms, including persistent fatigue, emotional lability, and low mood. When clinically indicated, cortisol testing may be considered.
Medications and Substances That May Contribute to Depressive Symptoms
Mood changes can also be a side effect of medications or substances rather than a primary psychiatric condition. A thorough medication review is a standard part of any mood evaluation.
Commonly Prescribed Medications with Mood-Related Side Effects
Several classes of medication have been associated with depressive symptoms in some patients, including:
- Beta-blockers (e.g., metoprolol, propranolol) — used for cardiovascular conditions; while large clinical trials show they do not cause depression, side effects like fatigue and sleep disruption can closely mimic depressive symptoms
- Corticosteroids (e.g., prednisone) — used for inflammatory conditions
- Isotretinoin — used for severe acne
- Oral contraceptives — hormonal contraceptives may affect mood in some individuals
- Proton pump inhibitors (PPIs) — long-term use may contribute to B12 depletion
- Interferon and certain antiviral medications
Any medication concerns must be discussed directly with the prescribing provider before making any changes.
Alcohol, Cannabis, and Mood
Alcohol is a central nervous system depressant. Regular or heavy alcohol use can produce or worsen depressive symptoms and disrupt sleep architecture. Cannabis has a variable relationship with mood — in some individuals it may worsen depressive and anxiety symptoms over time. An accurate substance use history is an essential component of the depression evaluation.
What a Medical Evaluation for Depression Looks Like at Stay Healthy Med
At Stay Healthy Med in Tallahassee, FL, Brandi Richardson, APRN, provides an integrated approach that combines the diagnostic capabilities of adult primary care with the clinical expertise of psychiatric mental health care.
Clinical Interview and Symptom History
Every evaluation begins with a thorough clinical interview covering mood symptoms, their duration and onset, functional impact, relevant personal and family medical history, current medications, substance use history, and sleep patterns. Validated tools such as the PHQ-9 are used to assess symptom severity.
Laboratory Panel — What May Be Ordered and Why
Based on the clinical interview and individual presentation, laboratory testing may be ordered to evaluate for medical contributors to mood symptoms. A standard panel may include:
- TSH and Free T4 — Thyroid function
- CBC with Differential — Anemia screening
- Serum Ferritin — Iron stores
- 25-OH Vitamin D — Vitamin D status
- Serum Vitamin B12 and RBC Folate — Neurological nutrient status
- Comprehensive Metabolic Panel (CMP) — Kidney, liver, glucose
- HbA1c — Long-term blood sugar control
Not every patient requires every test. The specific panel is individualized based on clinical history, risk factors, and symptom pattern.
The Integrated Advantage — Primary Care and Psychiatry in One Visit
Unlike a standalone psychiatric practice or therapy-only setting, Stay Healthy Med offers the ability to address both the medical evaluation and the psychiatric assessment within the same clinical relationship. Patients do not need to coordinate between multiple providers to receive a comprehensive workup — reducing fragmentation, delays, and the risk of important medical contributors being overlooked.
When the Medical Rule-Out Is Negative — What Happens Next
A Normal Lab Panel Does Not Mean Symptoms Are Not Real
Depression is a biologically based condition with measurable effects on brain chemistry and neurological function. A normal laboratory workup confirms, not questions, the legitimacy of the mood disorder. It is often a clinically valuable step in building a clear diagnostic picture.
Moving Forward with a Psychiatric Treatment Plan
When medical contributors have been evaluated, the clinical focus shifts to evidence-based psychiatric treatment. Depending on the individual’s diagnosis and history, this may include antidepressant medication management, referral to psychotherapy, treatment of comorbid conditions, and appropriate follow-up lab monitoring.
For adults also managing ADHD alongside depression, our comprehensive adult ADHD evaluation in Tallahassee provides a related clinical resource.
Schedule a Comprehensive Depression Evaluation in Tallahassee, FL
If you have been experiencing persistent low mood, fatigue, loss of motivation, or difficulty concentrating, a comprehensive evaluation at Stay Healthy Med can help clarify whether medical factors are contributing to your symptoms — and what the most effective path forward looks like for you.
Brandi Richardson, APRN, accepts new patients for outpatient psychiatry and primary care services in Tallahassee, FL, including in-person visits at 325 John Knox Road, Suite L103, Tallahassee, FL 32303, and telehealth appointments for patients across Florida.
Phone: (850) 329-2913
Visit our appointments page to request a new patient appointment.
Mental health care that sees the whole person — mind, body, and history. That is the Stay Healthy Med difference.
Clinically reviewed by Brandi Richardson, APRN, Nurse Practitioner — Adult-Gerontology Primary Care and Psychiatric Mental Health, Stay Healthy! LLC, Tallahassee, FL.
