Residency · Residency · Family Medicine

Depression in Primary Care: Screening, Diagnosis, and Stepped Care

Introduction

Depression is one of the most common conditions encountered in family medicine, affecting approximately 8% of adults in any given two-week period. Primary care physicians diagnose and manage the majority of depression cases, making competence in screening, diagnosis, and evidence-based treatment essential for every family medicine resident.

Epidemiology and Risk Factors

The lifetime prevalence of major depressive disorder (MDD) is approximately 20% in women and 12% in men. Peak onset occurs between ages 25 and 44, though depression affects all age groups. Key risk factors include family history of mood disorders, chronic medical illness (such as diabetes, heart failure, and chronic pain), adverse childhood experiences and ongoing psychosocial stressors, substance use disorders, and the postpartum period and perimenopause.

Screening in Primary Care

Validated Screening Tools

The PHQ-2 is a two-item screener assessing depressed mood and anhedonia over the past two weeks, with a sensitivity of approximately 83% and specificity of approximately 92%. The PHQ-9 is a nine-item tool aligned with DSM-5 criteria, with scores categorizing severity: 5 indicates mild, 10 moderate, 15 moderately severe, and 20 severe depression.

USPSTF Recommendations

The USPSTF recommends screening all adults aged 19 and older, including pregnant and postpartum individuals (Grade B recommendation). Screening should be implemented with adequate systems for diagnosis, treatment, and follow-up.

Diagnosis

DSM-5 Criteria for Major Depressive Disorder

Diagnosis requires five or more of the following symptoms during the same two-week period, representing a change from baseline, with at least one symptom being depressed mood or loss of interest: depressed mood most of the day, nearly every day; anhedonia (markedly diminished interest or pleasure); significant weight change or appetite disturbance; insomnia or hypersomnia; psychomotor agitation or retardation; fatigue or loss of energy; feelings of worthlessness or excessive guilt; diminished concentration or indecisiveness; and recurrent thoughts of death or suicidal ideation.

Differential Diagnosis

The differential includes bipolar disorder (always screen for prior manic episodes with the MDQ before starting antidepressants), hypothyroidism, anemia, vitamin B12 or folate deficiency, substance-induced mood disorder, and adjustment disorder, grief, or persistent depressive disorder (dysthymia).

Initial Workup

The initial workup includes CBC, TSH, and a basic metabolic panel. Vitamin D, B12, and folate levels should be considered. A urine drug screen is appropriate when substance use is suspected.

Stepped Care Model

Step 1: Mild Depression (PHQ-9 5-9)

Mild depression is managed with watchful waiting and scheduled follow-up in two to four weeks, psychoeducation and self-management strategies, an exercise prescription of 150 minutes per week of moderate-intensity aerobic activity, and digital cognitive behavioral therapy (CBT) programs.

Step 2: Moderate Depression (PHQ-9 10-14)

Moderate depression warrants first-line pharmacotherapy with SSRIs (such as sertraline or escitalopram) or SNRIs (such as venlafaxine or duloxetine), along with referral for structured psychotherapy (CBT or interpersonal therapy). The combination of medication and therapy is more effective than either alone.

Step 3: Moderately Severe to Severe Depression (PHQ-9 15+)

For moderately severe to severe depression, antidepressant medication is strongly recommended along with combined medication and psychotherapy. Psychiatric consultation should be considered for treatment-resistant cases, and safety assessment is essential at every visit.

Step 4: Treatment-Resistant or Complex Depression

Treatment-resistant depression may benefit from augmentation strategies such as adding bupropion, aripiprazole, or lithium, or switching to a different antidepressant class. Referral to psychiatry is appropriate for consideration of esketamine, transcranial magnetic stimulation (TMS), or electroconvulsive therapy (ECT).

Antidepressant Prescribing Pearls

Treatment should begin at a low dose and be titrated to the therapeutic dose over two to four weeks. Patients should be educated that full therapeutic effect takes four to six weeks. Monitoring for activation syndrome and suicidality is important in adolescents and young adults, as there is an FDA black box warning for ages under 25. A minimum of six to nine months of treatment is recommended for a first episode, with longer treatment for recurrent episodes. Gradual tapering is essential to avoid discontinuation syndrome, especially with paroxetine and venlafaxine.

Follow-Up and Monitoring

The PHQ-9 should be repeated at every follow-up visit to track response. Response is defined as a 50% or greater reduction in PHQ-9 score, and remission is defined as a PHQ-9 score less than 5. Follow-up should be scheduled at two, four, eight, and twelve weeks after starting treatment.

Clinical Pearls

Always screen for bipolar disorder before initiating antidepressants, as antidepressants without a mood stabilizer can trigger mania. PHQ-9 item 9, which addresses thoughts of death or self-harm, should always prompt a direct suicide risk assessment. Sertraline is preferred in patients with comorbid cardiac disease due to its favorable safety profile. Collaborative care models that integrate behavioral health into primary care improve outcomes by 50% compared with usual care. Cultural factors in the presentation of depression should be considered, as somatic complaints may predominate in some populations.

References

1. Kroenke K, Spitzer RL, Williams JBW. The PHQ-9: validity of a brief depression severity measure. J Gen Intern Med. 2001;16(9):606-613.
2. US Preventive Services Task Force. Screening for depression in adults: recommendation statement. JAMA. 2023;329(23):2057-2067.
3. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 5th ed., text revision. Washington, DC: APA; 2022.
4. Archer J, Bower P, Gilbody S, et al. Collaborative care for depression and anxiety problems. Cochrane Database Syst Rev. 2012;10:CD006525.

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