Assess and Confirm Diagnosis of Major Depressive Disorder (MDD)

When initial screening is positive, consider further assessment to confirm that criteria are met for major depressive disorder.

Assess

• Offer the person an opportunity to talk, preferably in a private space. Ask for the person’s subjective understanding of his or her symptoms.
• Ask about current psychosocial stressors (see ementalhealth.ca for local resources that could be of help)
• Assess and manage any situation of maltreatment, abuse (e.g. domestic violence) and neglect
• Ask about past psychiatric history, including a history of depression
• Ask about a family history of psychiatric illness
• Ask about social supports and coping strategies
• Consider assessing functioning using the Workplace and Social Adjustment Scale
• Check for accompanying anxiety using the  GAD7

Confirm Diagnosis of Depression

Ask directly in your clinical interview and confirm that DSM-5 criteria (see below) are met, and

Consider using standardized questionnaires such as the PHQ-9

• Interpreting the PHQ-9
• PHQ-9 (PDF)
• PHQ-9 (Online from MDCalc.com)
• PHQ-9 in other languages 

Rule out contributory medical conditions, that might better explain the symptoms of depression:

• Do physical exam
• Consider doing CBC, lytes, BUN, Cr, Glucose, B12, folate, TSH
• If indicated, consider other investigations such as:
  • Sleep study if there are symptoms such as excessive daytime sleepiness that might suggest sleep disorder such as sleep apnea, restless legs, periodic limb movement disorder, etc. Lausanne NoSAS score for sleep apnea.pdf
  • CT/MRI if there are focal neurologic symptoms suggesting focal lesions

Rule out main psychiatric differential diagnoses such as:

• Substance Abuse
  • For alcohol Consider using Audit-C
  • For drug use ask "How many times in the past year have you used an illegal drug or used a prescription medication for non-medical reasons?" (response of 1 or greater is considered positive)
    • if positive response Consider using DAST-10
•  Bipolar Disorder
  • Consider using MDQ 
    • Note: this is a screening not a diagnostic tool

DSM-5 Criteria for your reference

A. Five (or more) of the following symptoms have been present during the same 2-week period and represent a change from previous functioning; at least one of the symptoms is either (1) depressed mood or (2) loss of interest or pleasure.

Note: Do not include symptoms that are clearly attributable to another medical condition.

1. Depressed mood most of the day, almost every day. Mood is classically sadness but can also include emptiness, hopelessness or irritability.
2. Markedly diminished interest or pleasure in all or almost all activities most of the day nearly every day.
3. Significant weight loss when not dieting or weight gain.
4. Inability to sleep or oversleeping nearly every day.
5. Psychomotor agitation or retardation nearly every day.
6. Fatigue or loss of energy nearly every day.
7. Feelings of worthlessness or excessive or inappropriate guilt (which may be delusional) nearly every day.
8. Diminished ability to think or concentrate, or indecisiveness, nearly every day.
9. Recurrent thoughts of death (thoughts such as wanting to die, not just fear of dying), recurrent suicidal ideation without a specific plan, or a suicide attempt or a specific plan for committing suicide.

B. Symptoms cause clinically significant distress or impairment in social, occupational, or other important areas of functioning

C. The episode is not due to the effects of a substance or to a medical condition

D. The occurrence is not better explained by schizoaffective disorder, schizophrenia, schizophreniform disorder, delusional disorder, or other specified and unspecified schizophrenia spectrum and other psychotic disorders

E. There has never been a manic episode or a hypomanic episode