Major Depressive Disorder & Anxiety Disorders in Adults & Older Adults

Major Depressive Disorder and Anxiety Disorders across the Adult Lifespan

Psychiatric disorders, specifically Major Depressive Disorder (MDD) and Generalized Anxiety Disorder (GAD), represent major causes of disability and functional impairment in primary care. In older adults, psychiatric illnesses frequently manifest with atypical somatic symptoms, executive dysfunction, or overlap with chronic medical comorbidities. The advanced practice registered nurse (APRN) must apply rigorous diagnostic criteria, utilize validated screening instruments, adhere to geriatric prescribing guidelines (such as the American Geriatrics Society Beers Criteria 2023), and execute structured suicide risk evaluations.

Major Depressive Disorder (MDD): Diagnostic Criteria and Screening

DSM-5-TR Diagnostic Criteria

According to the DSM-5-TR, a formal diagnosis of Major Depressive Disorder requires the presence of at least 5 of 9 clinical symptoms during the same continuous 2-week period, representing a clear change from baseline functioning. At least one of the symptoms must be either:

1. Depressed mood most of the day, nearly every day.
2. Anhedonia (markedly diminished interest or pleasure in activities).

The constellation of 9 potential symptoms is recalled using the mnemonic SIGECAPS:

• S - Sleep Disturbances: Insomnia (middle insomnia or terminal early-morning awakening) or hypersomnia nearly every day.
• I - Interest Loss (Anhedonia): Significant decline in pleasure or motivation for previously enjoyed activities.
• G - Guilt or Worthlessness: Excessive, inappropriate feelings of self-reproach or worthlessness.
• E - Energy Loss: Daily fatigue or loss of physical vitality.
• C - Concentration Impairment: Diminished ability to think, focus, or make everyday decisions.
• A - Appetite and Weight Changes: Significant weight loss when not dieting or weight gain (> 5% body weight in a month), or appetite changes.
• P - Psychomotor Alterations: Psychomotor agitation (restlessness) or retardation (slowness of speech and movement).
• S - Suicidal Ideation: Recurrent thoughts of death, suicidal ideation without a specific plan, or a suicide attempt/plan.

Clinical Presentation in Older Adults and Pseudodementia

In older adults, depression often presents atypically with somatic complaints—such as fatigue, unexplained pain, gastrointestinal distress, or cognitive complaints ("pseudodementia"). Differentiating pseudodementia from true dementia is critical:

• Depression (Pseudodementia): Subacute onset; patient highlights memory deficits; answers test questions with "I don't know" or poor effort; performance on cognitive testing fluctuates; mood disturbance precedes memory complaints.
• Dementia: Insidious onset; patient minimizes memory deficits; attempts to answer questions and confabulates; exhibits consistent cognitive deficits; memory impairment precedes affective changes.

Validated Clinical Screening Instruments

• PHQ-2: Rapid 2-item initial screen assessing depressed mood and anhedonia over the prior 2 weeks. A score >= 3 is positive, mandating completion of the PHQ-9.
• PHQ-9: 9-item tool corresponding to DSM-5 criteria: Mild (5–9), Moderate (10–14), Moderately Severe (15–19), and Severe (>= 20). A 50% reduction in baseline PHQ-9 score defines clinical response; a score < 5 indicates remission.
• Geriatric Depression Scale (GDS-15): 15-item binary (Yes/No) questionnaire validated for adults aged 65 and older. By omitting somatic symptoms (sleep, fatigue, appetite) that overlap with physical illness, the GDS-15 avoids false-positive diagnoses. A score >= 5 suggests depression.

Evidence-Based Pharmacotherapy and Beers Criteria 2023 Warnings

SSRIs and SNRIs constitute first-line pharmacotherapy for MDD and anxiety. Drug selection in older adults requires strict adherence to safety profiles.

Preferred Antidepressants in Older Adults

• Sertraline (Zoloft): Excellent cardiac safety profile; preferred in patients with ischemic heart disease or post-myocardial infarction. Minimal CYP450 drug interactions.
• Escitalopram (Lexapro): Clean pharmacokinetic profile with minimal drug interactions. Max dose in older adults is 10 mg daily due to QTc prolongation risks.
• Mirtazapine (Remeron): Alpha-2 antagonist and 5-HT2/5-HT3 blocker. At low doses (7.5–15 mg daily at bedtime), H1-antagonism causes sedation and appetite stimulation. Ideal for frail, underweight older adults with depression, insomnia, and anorexia.
• Duloxetine (Cymbalta): Dual SNRI indicated for co-occurring depression and chronic pain syndromes (diabetic peripheral neuropathy, fibromyalgia).

Antidepressants to Avoid in Older Adults (Beers Criteria 2023)

• Paroxetine (Paxil): Strongly anticholinergic SSRI. Causes dry mouth, constipation, urinary retention (exacerbating BPH), confusion, orthostasis, and fall risk. Listed on the Beers Criteria as inappropriate for older adults.
• Fluoxetine (Prozac): Prolonged elimination half-life (active metabolite half-life up to 15 days), causing drug accumulation, agitation, insomnia, and CYP2D6/3A4 drug interactions in older adults.
• Tricyclic Antidepressants (TCAs) (Amitriptyline, Imipramine, Doxepin > 6 mg): Highly anticholinergic, sedating, cause severe orthostatic hypotension, and carry cardiac conduction toxicity. Avoid in older adults.
• Bupropion (Wellbutrin): Norepinephrine-dopamine reuptake inhibitor (NDRI). Useful for depression with fatigue or tobacco cessation; lacks sexual side effects. Absolute Contraindications: Seizure disorders, bulimia, or anorexia nervosa.

Generalized Anxiety Disorder (GAD) and Benzodiazepine Risks

Generalized Anxiety Disorder (GAD) involves excessive, uncontrollable worry occurring more days than not for at least 6 months. It requires at least 3 of 6 symptoms: restlessness, fatigue, concentration difficulties, irritability, muscle tension, or sleep disturbance.

• GAD-7 Scale: Standardized 7-item screen: Mild (5–9), Moderate (10–14), Severe (>= 15).
• First-Line Pharmacotherapy: SSRIs (Sertraline, Escitalopram) or SNRIs (Duloxetine, Venlafaxine). Initiate at half standard dose ("start low, go slow") to avoid activation anxiety. Buspirone is a non-sedating, non-addictive option for GAD.
• Beers 2023 Benzodiazepine Warning: Benzodiazepines (Diazepam, Lorazepam, Alprazolam) should be strictly avoided in older adults. They increase risks of cognitive impairment, delirium, motor vehicle accidents, falls, and hip fractures. If short-term bridging is unavoidable in younger adults, use agents without active metabolites (LOT: Lorazepam, Oxazepam, Temazepam).

Psychotherapy and Comprehensive Suicide Risk Assessment

• Cognitive Behavioral Therapy (CBT): First-line non-pharmacological treatment for MDD and GAD. Focuses on identifying automatic negative thoughts, cognitive restructuring, and behavioral activation.
• Suicide Risk Assessment: Older white males aged 85 and older have the highest suicide rate of any demographic. NPs must perform structured evaluations using the Columbia-Suicide Severity Rating Scale (C-SSRS), evaluating: Ideation, Plan, Intent, and Access to lethal means.

Emergency Intervention: Active suicidal ideation with plan, intent, or access to means requires immediate continuous observation, safety protocol activation, emergency evaluation, and crisis psychiatric admission.