How do you diagnose and treat a patient suspected of having major depression, considering their demographic information, medical history, and potential contributing conditions?

Testing for Major Depression

Use the Patient Health Questionnaire-9 (PHQ-9) or structured diagnostic interviews based on DSM-5 criteria to diagnose major depressive disorder, requiring at least 5 symptoms present for at least 2 weeks, including either depressed mood or anhedonia, plus additional symptoms such as sleep changes, appetite changes, psychomotor changes, fatigue, guilt/worthlessness, concentration problems, or suicidal ideation. 1

Diagnostic Criteria

Major depressive disorder requires a minimum 2-week duration of symptoms that interfere with daily functioning. 1, 2, 3 The diagnosis mandates at least 5 of the following symptoms, with at least one being either depressed mood or loss of interest/pleasure (anhedonia):

• Depressed mood most of the day, nearly every day 1
• Markedly diminished interest or pleasure in activities (anhedonia) 1
• Significant weight change or appetite disturbance 2, 3
• Insomnia or hypersomnia 1, 2
• Psychomotor agitation or retardation 2, 3
• Fatigue or loss of energy 1, 2
• Feelings of worthlessness or excessive guilt 1, 2
• Diminished ability to think, concentrate, or make decisions 1, 2
• Recurrent thoughts of death or suicidal ideation 2, 3

Validated Assessment Tools

The PHQ-9 and Hamilton Depression Rating Scale (HAM-D) are the primary screening instruments for assessing depression severity and monitoring treatment response. 1 These tools have sensitivity of 80-90% but specificity of only 70-85%, meaning approximately 24-40% of positive screens will have major depression when prevalence is 5-10%. 4

Additional validated instruments include:

• Montgomery-Åsberg Depression Rating Scale (MADRS) 1
• Quick Inventory of Depressive Symptomatology Self-Report (QIDS-SR) 1
• Mini International Neuropsychiatric Interview for structured diagnosis 1
• Structured Clinical Interview based on DSM-5 criteria 1

Screening can be accomplished in less than 5 minutes, and shorter instruments asking only about depressed mood and anhedonia detect the majority of depressed patients. 4

Critical Differential Diagnosis Considerations

Before confirming major depression, rule out secondary depression from medical conditions, medications, substance use, or other psychiatric disorders. 5, 6, 7

Medical Conditions to Exclude:

• Hypothyroidism, hyperthyroidism, and other endocrine disorders 6, 7
• Neurologic conditions (stroke, Parkinson's disease, multiple sclerosis, dementia) 7, 8
• Chronic systemic illnesses (diabetes, cardiovascular disease, chronic pain) 7, 8
• Malignancies 7
• Delirium (particularly in medically ill patients) 7

Medication-Induced Depression:

Review all current medications, as many drugs can cause depressive symptoms, including corticosteroids, beta-blockers, and certain antihypertensives. 6, 7

Substance Use:

Screen for alcohol and substance abuse, as depressive symptoms occur in up to 30% of those with alcohol use disorder; abstinence is essential before confirming primary depression. 9

Bipolar Disorder Screening:

Prior to initiating antidepressant treatment, screen all patients for bipolar disorder risk through detailed psychiatric history, including family history of bipolar disorder, suicide, and depression, as treating bipolar depression with antidepressants alone may precipitate manic episodes. 2

Special Population Considerations

Patients with Diabetes:

Screen annually for depression in all diabetic patients using age-appropriate validated measures, with particular attention to those with self-reported depression history. 4 Elevated depressive symptoms affect one in four patients with type 1 or type 2 diabetes, with women having significantly higher rates than men. 4

Reassess for depression at diagnosis of diabetic complications or significant medical status changes. 4

Elderly Patients:

Depression is not a normal part of aging; evaluate elderly patients with the same diagnostic criteria, recognizing that medical comorbidities and psychosocial stressors are common confounders. 9

Patients with Serious Mental Illness:

Monitor patients with schizophrenia and other thought disorders for depression, as they have significantly increased rates of comorbid major depression. 4

Screening Intervals and Follow-Up

The optimal screening interval is unknown, but recurrent screening is most productive in patients with depression history, unexplained somatic symptoms, comorbid anxiety or panic disorder, substance abuse, or chronic pain. 4

For patients with prior depression, conduct ongoing monitoring within routine care to detect recurrence. 4

Critical Pitfall: Positive Screens Require Diagnostic Confirmation

A positive screening result mandates further diagnostic questioning to establish the diagnosis and rule out other conditions. 4 Approximately 60-76% of positive screens will be false positives or represent other conditions (dysthymia, subsyndromal depression, anxiety disorders, substance abuse, grief reactions). 4

Suicidality Assessment

Directly assess for suicidal ideation, plans, and intent in all patients with suspected depression, as nearly 60% of suicides are rooted in major depression. 9 This assessment should include:

• Current suicidal thoughts 2, 3
• Specific plans or means 9
• Prior suicide attempts 9
• Family history of suicide 2
• Access to lethal means 9

Monitor suicidality closely during initial treatment and dose changes, as antidepressants increase risk for suicidal thinking and behavior in younger patients, particularly those under age 25. 2