Differential Diagnosis for Major Depressive Disorder with General Anxiety Disorder

Single Most Likely Diagnosis

• Major Depressive Disorder (MDD) with Anxious Distress: This is the most straightforward diagnosis given the symptoms of major depressive disorder combined with significant anxiety, which is a common comorbidity. The presence of anxiety can sometimes complicate the diagnosis but is a recognized specifier in DSM-5.

Other Likely Diagnoses

• Generalized Anxiety Disorder (GAD): While GAD is mentioned in the context of MDD, it's possible for GAD to be the primary diagnosis if the anxiety symptoms are predominant and the depressive symptoms are secondary or less severe.
• Anxiety Disorder Due to Another Medical Condition: If there's an underlying medical condition that could be causing or contributing to the anxiety symptoms, this diagnosis should be considered. Certain medical conditions can manifest with anxiety and depressive symptoms.
• Substance-Induced Depressive Disorder or Anxiety Disorder: Substance use or withdrawal can cause symptoms that mimic MDD or GAD. A thorough substance use history is essential to rule out this possibility.

Do Not Miss Diagnoses

• Bipolar Disorder: It's crucial not to miss bipolar disorder, especially bipolar II, where depressive episodes are more common than manic episodes, and anxiety can be a significant symptom. Missing this diagnosis could lead to inappropriate treatment with antidepressants, which can induce mania.
• Post-Traumatic Stress Disorder (PTSD): PTSD can present with depressive and anxiety symptoms. A traumatic event history is key to diagnosing PTSD, and missing it could lead to inadequate treatment.
• Thyroid Disorders: Both hypothyroidism and hyperthyroidism can cause symptoms of depression and anxiety. These conditions are easily missed but can be diagnosed with simple blood tests.
• Sleep Disorders: Sleep apnea, insomnia, and other sleep disorders can cause significant anxiety and depressive symptoms. Treating the underlying sleep disorder can significantly improve mental health symptoms.

Rare Diagnoses

• Neurodegenerative Disorders (e.g., Frontotemporal Dementia, Huntington's Disease): In rare cases, neurodegenerative diseases can present with psychiatric symptoms, including depression and anxiety, before more typical neurological symptoms appear.
• Wilson's Disease: This is a rare genetic disorder that can cause psychiatric symptoms, including depression and anxiety, along with neurological and hepatic symptoms.
• Cushing's Syndrome: This endocrine disorder can cause a range of psychiatric symptoms, including depression and anxiety, due to excess cortisol levels.

Each of these diagnoses requires careful consideration of the patient's history, physical examination, and sometimes additional diagnostic tests to accurately diagnose and treat the condition.