4.2.1 Unipolar Depressive Disorders & Major Depressive Disorder

Classification of Depressive Disorders in DSM-5

• Primary distinction: unipolar vs bipolar depression
• Unipolar depressive disorders
  • Major Depressive Disorder (MDD)
  • Persistent Depressive Disorder (PDD – formerly dysthymia)
  • Premenstrual Dysphoric Disorder (PMDD)
  • Disruptive Mood Dysregulation Disorder (childhood-onset)

Major Depressive Disorder (MDD)

Core Diagnostic Framework

• Must exhibit $\geq 5$ symptoms in the same $2$-week window
• Represents a change from previous functioning
• At least one of the following must be present:
  • Depressed mood
  • Loss of interest/pleasure (anhedonia)
• Rule-outs: symptoms fully accounted for by medical condition or substances are excluded

Symptom Inventory (need ≥5)

1. Depressed mood most of day, nearly every day
   • Self-report (sad, empty, hopeless) or observed (tearful)
   • In youth: irritability can substitute
2. Markedly diminished interest/pleasure in almost all activities
3. Significant weight/appetite change
   • Weight loss or gain >$5\%$ in $1$ mo
   • Children: failure to achieve expected weight gain
4. Sleep disturbance – insomnia or hypersomnia
5. Psychomotor change – agitation or retardation (observable)
6. Fatigue / loss of energy
7. Worthlessness / excessive or delusional guilt
8. Diminished concentration / indecisiveness
9. Recurrent thoughts of death or suicide (ideation, plan, or attempt)

Functional & Exclusion Criteria

• Causes clinically significant distress or impairment (social, occupational, etc.)
• Not better explained by substances or medical illness

Course Characteristics

• Untreated episode length: $6{-}9$ mo
• $10{-}20\%$ remain symptomatic >2 yr → may meet PDD criteria
• Remission: $\geq 2$ mo symptom-free
  • Relapse: return of same episode (often after stopping meds)
  • Recurrence: new episode after $\geq 6$ mo remission
• Onset: late adolescence → middle adulthood, but possible from childhood to old age

Epidemiology in Youth

• School-age prevalence: $1{-}3\%$
• Adolescents with MDD: $15{-}20\%$; additional $10{-}20\%$ subclinical
• Sex difference emerges in adolescence
• Early onset → poorer adult outcomes & high recurrence (Rudolph $2017$)

Specifiers: Tailoring the Diagnosis

(Additions to indicate course, severity, or special features; guide treatment)

Anxious Distress

• $\geq 2$: tension, restlessness, worry-based concentration deficits, generalized fear, fear of losing control
• Correlates: higher suicide risk, longer illness, poorer treatment response

Melancholic Features

• Near-total loss of capacity for pleasure (not merely diminished)
• Diagnostic cues – need $\geq 3$:
  1. Profound despondency/emptiness
  2. Worse mood in morning
  3. Early-morning awakening (≥$2$ h early)
  4. Marked psychomotor change
  5. Significant anorexia/weight loss
  6. Excessive/inappropriate guilt
• Prevalence ≈$23.5\%$ of unipolar cases; increases with low light/temperature
• Often responds well to antidepressants or ECT

Psychotic Features (Mood-Congruent)

• Delusions/hallucinations whose content mirrors depressive themes (inadequacy, guilt, death)
• Leads to longer episodes, more cognitive impairment, poorer prognosis
• Treatment: antidepressant + antipsychotic or ECT

Atypical Features

• Mood reactivity (brightens to positive events) plus $\geq 2$ of:
  1. Significant weight gain / increased appetite
  2. Hypersomnia (≥$10$ h total sleep per day)
  3. Leaden paralysis (heavy limbs ≥$1$ h/day)
  4. Chronic rejection sensitivity (persists in remission)
• Demographics: more female, earlier onset, higher suicidality
• Better response to MAOI medications; linked to bipolar spectrum (hypomania)

Catatonic Features

• Prominent psychomotor disturbance ranging from immobility/catalepsy & mutism to purposeless agitation
• Historically tied to schizophrenia but more common in mood disorders

Seasonal Pattern (Seasonal Affective Disorder)

• Regular temporal link between episodes & season (typically winter onset, summer remission)
• Pattern stable ≥$2$ yrs; characteristic somatic signs: hypersomnia, carb craving, weight gain, fatigue
• Occurs in ≈$\frac{1}{6}$ of patients with ≥$3$ prior episodes; more common in unipolar & bipolar II
• Exclude episodes driven by seasonal employment or other psychosocial stressors

Peripartum Onset

• Onset during pregnancy or within months postpartum; prevalence $3{-}6\%$
• $\approx 50\%$ begin before delivery
• Often severe anxiety/panic; risk factors = prior mood disorder (esp. bipolar I) & family history
• Postpartum psychosis with command hallucinations to harm infant: $1/500{-}1/1000$ births

Severity Specifiers

• Mild: ≈$2$ symptoms, minor impairment
• Moderate: ≈$3$ symptoms
• Moderate-severe: $4{-}5$ symptoms
• Severe: ≥$4{-}5$ plus marked psychomotor agitation/retardation or pronounced functional loss

Course, Relapse, & Treatment Implications

• Chronic MDD → greater suicide risk, poorer remission
• Relapse often follows premature medication cessation
• Specifiers guide therapy choices:
  • Melancholic → pharmacotherapy, ECT
  • Atypical → MAOIs, light therapy (if seasonal)
  • Psychotic → combo antidepressant + antipsychotic
  • Anxious distress → integrate anxiolytics/CBT focusing on worry

Developmental & Lifespan Notes

• Children: irritability & weight-gain failure key markers
• Adolescents: high prevalence, emerging sex disparity, long-term psychosocial impact
• Elderly: melancholia common; risk of misdiagnosis as dementia

Ethical & Practical Considerations

• Accurate specifier use critical for suicide-risk evaluation & personalized care
• Must rule out medical/substance causes to avoid mis-diagnosis
• Consider environmental stressors (seasonal work, peripartum context) before labeling intrinsic pathology

Integrative Connections

• Cognitive distortions (self-blame, catastrophizing) fuel guilt criteria
• Circadian rhythm disruption (early awakening) links biology to melancholic subtype
• Chronicity & relapse patterns mirror other recurrent illnesses → need long-term maintenance plans