Psychiatric Epidemiology

Psychiatric Epidemiology - Epi Essentials

• Epidemiology: Study of distribution & determinants of health-related states in populations, and application to control health problems.
• Psychiatric Epidemiology: Epidemiology focused on occurrence, distribution, and determinants of mental disorders.
• Aims:
  • Describe distribution of psychiatric disorders.
  • Identify etiological factors.
  • Provide data for planning & evaluation of mental health services.
• Key Measures:
  • Incidence: New cases in a population at risk over time. $I = \frac{\text{No. of new cases in a specific period}}{\text{Total population at risk during that period}}$
  • Prevalence: Total existing cases in a population at a point or over a period. (Types: 📌 Point, Period, Lifetime - PPL)
    • Point Prevalence: At a specific point in time. $P_{\text{point}} = \frac{\text{No. of current cases at a specific point in time}}{\text{Total population at that same point in time}}$
    • Period Prevalence: Over a defined duration. $P_{\text{period}} = \frac{\text{No. of current cases over a specific period}}{\text{Average population during that period}}$
    • Lifetime Prevalence: Proportion who have ever had the disorder.

⭐ Lifetime prevalence is generally the highest type of prevalence reported for psychiatric disorders.

Psychiatric Epidemiology - Study Blueprints

• Descriptive Studies:

  • Cross-sectional: "Snapshot" of prevalence at a point in time.
  • Case series/reports: Detailed accounts of individual or few cases.
  • Ecological: Uses population-level data; risk of ecological fallacy.

• Analytical Studies:

  Feature	Case-Control Studies	Cohort Studies
  Design	Retrospective (Outcome → Exposure)	Prospective/Retrospective (Exposure → Outcome)
  Starts with	Cases (disease) & Controls (no disease)	Exposed & Non-exposed groups
  Measures	Odds Ratio (OR) = $ad/bc$	Relative Risk (RR) = $(a/(a+b))/(c/(c+d))$
  Best for	Rare diseases, long latency	Rare exposures, establishing incidence
  Pros	Quick, inexpensive, good for rare diseases	Establishes temporality, calculates incidence
  Cons	Recall bias, selection bias, no incidence	Expensive, time-consuming (prospective), attrition

  ⭐ Cohort studies can establish temporality (exposure precedes outcome), a key aspect of causality, unlike case-control studies.

• Experimental Studies:

  • Randomized Controlled Trials (RCTs): Gold standard for intervention efficacy; assess causality directly.

Psychiatric Epidemiology - Disorder Data & Trends

National Mental Health Survey (NMHS) India 2015-16 Highlights:

• Overall current prevalence of any mental morbidity: 10.6%.
• Nearly 15% of adults need active mental health interventions.
• Lifetime prevalence: 13.7%.

⭐ NMHS 2015-16: Common mental disorders (CMDs) like depression & anxiety are more prevalent than severe mental disorders (SMDs) in India.

Prevalence (Current) of Key Disorders (NMHS):

• Tobacco Use Disorder: 20.9%
• Mood Disorders (Depression, Bipolar): 5.6% (Depression 2.7%, Bipolar 0.6%)
• Alcohol Use Disorder: 4.6%
• Neurotic & Stress-Related (e.g., Anxiety): 3.5%
• Psychotic Disorders (e.g., Schizophrenia): 1.4%

Key Risk Factors:

• Age & Gender: e.g., Females ↑ depression/anxiety; Males ↑ substance use.
• Socioeconomic status: Lower SES ↑ risk.
• Family history of mental illness.
• Stressful life events (trauma, loss).

Protective Factors:

• Social support, positive coping skills, access to care.

Psychiatric Epidemiology - Screen, Prevent & Challenge

• Screening in Psychiatry:

  • Definition: Identifying unrecognized illness in apparently healthy individuals.
  • Purpose: Early detection for timely intervention, improved prognosis.
  • Good Test Criteria:
    • Validity: Accuracy (measures true status; sensitivity, specificity).
    • Reliability: Consistency (reproducible results; precision).

• Levels of Prevention:

• Challenges in Psychiatric Epidemiology:
  • Stigma: Causes underreporting and delays in seeking help.
  • Case Definition Variability: Inconsistent diagnostic criteria across studies.
  • Cultural Factors: Affect illness expression, reporting, help-seeking.
  • Comorbidity: Frequent co-occurrence of multiple psychiatric disorders.

⭐ Universal psychoeducation programs in schools, enhancing mental health literacy and coping skills, exemplify primary prevention in mental health.

High‑Yield Points - ⚡ Biggest Takeaways

• Prevalence measures existing cases; Incidence measures new cases in a defined period.
• Key types: Point prevalence, period prevalence, and lifetime prevalence.
• Anxiety and depressive disorders show high global and Indian prevalence.
• DALYs (Disability-Adjusted Life Years) reflect the total burden of mental illness.
• NMHS (National Mental Health Survey) is a vital source for Indian psychiatric epidemiology.
• Comorbidity of psychiatric disorders is frequent and impacts prognosis_._