Major Depressive Disorder (MDD) Clinical Overview
I. The "On-Call" Snapshot
Clinical Significance in Malaysia: This is one of the most common reasons for psychiatric admission and a frequent comorbidity in your medical and surgical patients, directly impacting their recovery and functional capacity. Your ability to screen, assess risk, and initiate basic management is non-negotiable.
High-Yield Definition: MDD is a mood disorder characterised by a persistent feeling of sadness or a loss of interest or pleasure, lasting for at least two weeks, accompanied by at least five of the nine diagnostic symptoms, causing clinically significant distress or impairment in social, occupational, or other important areas of functioning. (Adapted from DSM-5 criteria).
Clinical One-Liner: It's not just "feeling sad"; it's a persistent, debilitating medical illness that crushes a person's mood, energy, and will to function.
II. Etiology & Risk Factors
Etiology: We use a biopsychosocial model. It’s a mix of:
Biological: Neurotransmitter dysregulation (primarily Serotonin, Norepinephrine, Dopamine). Genetic predisposition plays a significant role.
Psychological: Maladaptive coping mechanisms, personality traits (e.g., neuroticism), history of trauma.
Social: Major adverse life events (bereavement, job loss), chronic stress, lack of social support.
Risk Factors:
Non-Modifiable:
Previous personal history of depression (strongest predictor).
Family history of mood disorders.
Female gender.
Post-partum period.
Modifiable:
Presence of chronic medical illness (e.g., Diabetes, IHD, CVA, Cancer).
Substance misuse (alcohol, illicit drugs).
Lack of a supportive social network.
Recent significant psychosocial stressors.
III. Quick Pathophysiology
The leading theory you need to know for management is the monoamine hypothesis. This suggests MDD is caused by a functional deficiency of serotonin (5-HT), norepinephrine (NE), and/or dopamine (DA) in the brain. This is the rationale for using antidepressants like SSRIs and SNRIs, which act by increasing the availability of these neurotransmitters in the synaptic cleft.
IV. Clinical Assessment
Red Flags & Immediate Actions:
Active suicidal ideation with a plan: -> Inform senior/psychiatry MO immediately. Ensure 1-to-1 nursing observation. Remove potential ligature points. Do not leave the patient alone.
Psychotic symptoms (delusions/hallucinations): -> Alert senior. Patient requires urgent psychiatric assessment, may need antipsychotics.
Catatonia or severe psychomotor retardation (refusing food/drink): -> Urgent review. This is a medical emergency due to risk of dehydration, malnutrition, and VTE.
Evidence of self-harm: -> Assess and manage physical injuries first (ABCDE). Then, proceed with psychiatric risk assessment.
History: Use the SIGECAPS mnemonic to screen for DSM-5 criteria over the last 2 weeks. You need ≥5 symptoms, and one must be depressed mood or anhedonia.
Sleep: Insomnia (especially early morning waking) or hypersomnia.
Interest: Loss of interest or pleasure (anhedonia).
Guilt: Feelings of worthlessness or excessive guilt.
Energy: Fatigue or loss of energy.
Concentration: Diminished ability to think or concentrate; indecisiveness.
Appetite: Significant weight loss or gain, or decrease/increase in appetite.
Psychomotor: Agitation or retardation observable by others.
Suicide: Recurrent thoughts of death, suicidal ideation, or attempt.
Pertinent Negatives: Crucially, ask about periods of elevated mood, hyperactivity, or decreased need for sleep to rule out Bipolar Disorder.
Physical Examination: The main goal is to rule out organic causes.
General: Look for signs of self-neglect, psychomotor retardation (slow movements), or agitation (pacing, hand-wringing). Note any scars from previous self-harm.
Specific Systems:
Neurological: Screen for focal deficits (to rule out CVA, space-occupying lesion).
Endocrine: Look for signs of hypothyroidism (goitre, dry skin, delayed reflex relaxation).
Mental State Examination (MSE): This is your core examination. Document Appearance, Behaviour, Speech, Mood, Affect, Thought (form & content), Perception, Cognition, and Insight.
Clinical Pearl: Always ask about suicide directly and professionally. "Sometimes, when people feel this low, they have thoughts of harming themselves. Have you had any such thoughts?" Direct questioning does not plant ideas; it opens the door for a patient to disclose risk. Always seek collateral history from family; patients may lack insight or under-report symptoms.
V. Diagnostic Workflow
Differential Diagnosis:
Bipolar Affective Disorder:
Points For: Presents with a depressive episode identical to MDD.
Points Against: No history of mania or hypomania.
How to Differentiate: A thorough history focusing on past episodes of elevated mood, increased energy, racing thoughts, and decreased need for sleep. Collateral history is key.
Anxiety Disorders (e.g., GAD):
Points For: High symptom overlap (fatigue, poor concentration, sleep disturbance).
Points Against: In GAD, worry and apprehension are primary; in MDD, low mood and anhedonia are primary.
How to Differentiate: Determine the predominant psychic symptom. Often, they are comorbid.
Organic Causes:
Points For: Can present with depressive symptoms.
Points Against: Presence of physical signs/symptoms or abnormal bloods.
How to Differentiate: A good clinical exam and baseline blood tests (especially TFTs).
Investigations Plan: Primarily to exclude organic differentials.
Bedside: Urine toxicology screen if substance misuse is suspected.
First-Line Labs:
Full Blood Count (FBC): To rule out anemia causing fatigue.
Renal Profile (RP): To check for electrolyte imbalance, uremia.
Liver Function Test (LFT): Baseline before starting antidepressants.
Thyroid Function Tests (TFTs): Hypothyroidism is a classic mimic of depression. This is mandatory.
Second-Line / Imaging:
CT Brain: Only indicated if the presentation is atypical (e.g., first episode in elderly >60 years, presence of focal neurological signs) to rule out an intracranial lesion.
VI. Staging & Severity Assessment
Severity dictates management. This is based on symptom count and functional impairment as per the Malaysian CPG for Management of MDD.
Mild Depression: 5-6 depressive symptoms. Minor functional impairment.
Management Impact: May be managed with watchful waiting, psychoeducation, and psychotherapy.
Moderate Depression: 7-8 depressive symptoms. Moderate functional impairment.
Management Impact: Antidepressants are indicated, usually alongside psychotherapy.
Severe Depression: 8-9 depressive symptoms. Severe functional impairment. May have psychotic features.
Management Impact: Antidepressants are first-line. Hospitalisation is often required, especially if suicide risk or psychotic features are present. Electroconvulsive Therapy (ECT) may be considered.
VII. Management Plan
Immediate Stabilisation (The ABCDE Plan):
A, B, C: Usually unremarkable unless there is a co-ingestion or self-inflicted injury.
D (Disability): Assess GCS. Primarily, assess and mitigate suicide risk.
E (Exposure/Environment): Ensure a safe environment. Remove any items the patient could use to harm themselves. Initiate constant observation if high risk.
Definitive Treatment (The Ward Round Plan):
First-Line Pharmacotherapy: Selective Serotonin Reuptake Inhibitors (SSRIs).
Drug of Choice (KKM Formulary): Fluoxetine or Sertraline.
Dosing: Start low, go slow. Fluoxetine 20mg OM. Review in 2 weeks for side effects, and 4-6 weeks for efficacy. Can increase to 40mg OM if needed.
Counselling: Warn patient about initial side effects (nausea, headache) which usually resolve in 1-2 weeks. Crucially, explain that the therapeutic effect is delayed for 4-6 weeks.
Non-Pharmacological:
Psychoeducation: Explain the diagnosis. Reassure them it is a treatable medical illness.
Psychotherapy: Refer for counselling or Cognitive Behavioural Therapy (CBT) if available.
Social: Involve medical social worker (MSW) if there are significant psychosocial stressors.
Referral: All new diagnoses of MDD, especially moderate-to-severe cases or those with suicide risk, should be referred to the psychiatry team for co-management.
Long-Term & Discharge Plan:
Medication: Continue antidepressant for at least 6-9 months after remission of the first episode to prevent relapse.
Follow-up: Arrange follow-up at the psychiatry clinic or a designated Klinik Kesihatan with a Family Medicine Specialist.
Return-to-work advice: Provide MC and advise a gradual return to work/duties.
VIII. Complications
Immediate:
Suicide/Self-Harm: Management: Ensure safety, psychiatric admission.
Short-Term:
Medication Side Effects: Management: Reassurance, symptomatic treatment, or switch agent if severe.
Social & Occupational Dysfunction: Management: Psychoeducation, social worker involvement, family meetings.
Long-Term:
Relapse/Recurrence: Management: Long-term or maintenance antidepressant therapy.
Increased Cardiovascular Morbidity/Mortality: Management: Actively screen for and manage cardiovascular risk factors.
IX. Prognosis
With treatment, about 60-70% of patients show significant improvement. However, relapse is common. About 50% will experience a second episode.
Top 3 Poor Prognostic Factors: Severe initial symptoms (especially psychosis), long duration of episode, and presence of comorbid substance misuse or personality disorder.
X. How to Present to Your Senior
"Dr, for review please. This is Puan Aminah in Bed 10, a 45-year-old lady with a background of T2DM, who was admitted for poor diabetic control. On clerking, she reports a one-month history of persistent low mood, loss of interest, poor sleep, and fatigue. She expresses feelings of worthlessness and has had fleeting thoughts of self-harm, though no active plan. My main differential is a moderate Major Depressive Episode. I have done a suicide risk assessment and initiated observation. Baseline bloods including TFTs are pending. I would like to ask about starting her on an SSRI like Fluoxetine 20mg and referring to the on-call psychiatry MO for their input."
XI. Summary & Further Reading
Top 3 Takeaways:
Always rule out organic causes. A TFT is not optional.
Always assess suicide risk directly. Document your assessment clearly.
SSRIs are first-line. Counsel the patient on the delayed onset of action and initial side effects.
Key Resources:
Malaysian CPG: Management of Major Depressive Disorder (Second Edition). Check the KKM website for the latest version.
UpToDate: Search for "Unipolar major depression in adults: Choosing initial treatment".
Review Article: Malhi GS, Mann JJ. Depression. Lancet. 2018;392(10161):2299-2312.
