PSYCHIATRIC EPIDEMIOLOGY

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PSYCHIATRIC EPIDEMIOLOGY
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Definition

• Study of the distribution of illness in
  populations over time and space
• The study of Mass aspects of disease
• The pursuit of recurrent and predictable patterns
  of behaviour in a given population

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Uses of Epidemiology

• Completing the clinical picture
• Community Diagnosis
• Secular changes in incidence
• Identification of Risk Factors/Protective
  Factors/Prevention
• Delineation of syndromes
• Planning services

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Epidemiology Terms

• Rates and Ratios
• Prevalence
• Point
• Period
• Lifetime
• Treated and untreated
• Inception (Incidence)

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Prevalence and Inception Rates

• Persons
• A -----------------------
• B ---------------
• C ------------
• D
  ------
• E
• ____________________________
• t0 t1
  t2 t3

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Base Population

• General population or population subgroup
• Primary care population
• Mental health service population
• Psychiatric Case Registers

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Epidemiological Research Design

• Cross-Sectional Studies
• Longitudinal Studies
• Prospective
• Retrospective
• Case-Control Studies
• Case Register Studies
• Any Epidemiological study can be Observational or
  Experimental

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Design of a Community Survey

• Defining the base population (sample frame)
• Sampling method
• Case Identification/definition (ascertainment)
• Survey Instruments
• Contact and Consent
• Interview
• Data entry and analysis

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The Problem of Psychiatric Case Definition

• Informal clinical judgement (Essen Moller,
  Hagnell,1966)
• Categorical and dimensional approaches (Srole et
  al, 1962)
• Reliability and Validity
• Computerized Diagnosis

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Sampling

• Individuals, households, addresses,postcodes
• Random sampling
• Stratified sampling
• Comparison with base population characteristics
• Sampling error, failure of the base population,
  non cooperation, and distorted data from
  respondents

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Instruments

• Questionnaires
• GHQ
• HAD
• Becks inventories
• Symptom checklists
• Rating scales
• Hamilton Depression Scale
• Bech Raphaelson Mania Rating Scale
• MIMS?

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Establishing a causal link between event and
disorder

• Case
• Yes
  No
• Yes a b
• Exposed
• No c d

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Instruments

• Interviews
• Structured (same questions asked of all subjects)
• Semi-structured ( same topics covered with some
  leeway for follow on questions
• Unstructured ( interviewer use their own clinical
  judgement)

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Structured Interviews

• Can be applied by trained lay persons
• Statements and wording pre-set
• Standard
• Examples
• DIS
• CIDI

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Semi-Structured interviews

• PSE
• SCAN
• CIS

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Issues of Reliability and Validity

• Reliability
• Interrater agreement
• Test-retest
• Validity
• Construct
• Content
• Correlation with gold standard

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Sensitivity and Specificity

• Cases by full
  psychiatric
  
• 
  assessment
• Yes
  No
• Cases by screening Yes a(TP) b(FP)
• Test
• No c(FN)
  d(TN)

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Chicago Study Faris and Dunham (1922-1934)

• 35,000 admissions to mental hospitals
• 1st admissions for schizophrenia highest in inner
  city areas within lowest socioeconomic groups
• Led to the social drift and social segregation
  hypotheses
• And to the social causation and social selection
  theories

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Midtown Manhattan Rennie and Srole (1954)

• 1660 adults, structured interview by non
  psychiatrists
• Incidence of mental disorder increased with age
• Low socioeconomic group had 6 times as many
  symptoms as those in the high groups

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New Haven Hollingshead and Redlich (1950)

• Social class and prevalence of treated mental
  disorder
• Census of psychiatric patients, community survey,
  survey of psychiatrists and controlled case study
• Described 5 distinct social classes and found
  neurosis in high classes, and psychosis more
  prevalent in lower classes
• 15.1 of population above 26 showed evidence of
  mental disorder

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Stirling County Alexander Leighton

• 20,000 rural persons ,non-clinicians, structured
  interview, later psychiatrist rating
• 24 had notable impairment, and 20 needed
  psychiatric attention
• Womengtmen, morbidity increases with age and
  poverty

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NIMH-ECA Survey Regier et al 1998-

• 20,000 from various sites across the US
• Structured interview, DIS, lay interviewers
• 15 one year prevalence of mental disorder in US
  population, 1/5 untreated, 1/5 treated by mental
  health, 3/5 primary care
• Depression women 2/men1
• Men more alcohol and substance misuse

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Psychiatric Morbidity in Upper Egypt (n5291)
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The Future of Psychiatric Epidemiology

• Molecular genetics and epidemiology
• Risk factors and dimensional measures of
  psychopathology
• Cross-national differences in the prevalence of
  disorder
• Changes over time (secular) changes in the
  pattern and prevalence of disorders

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• Group I Design an epidemiological study to test
  the hypothesis there is higher prevalence of
  psychosis in prisons compared to the general
  population.
• The design should include detecting associations
  with potential risk factors for any excess of
  psychotic disorders in persons serving a prison
  sentence

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• Design an epidemiological study that could
  determine the prevalence and demographic
  correlates of psychiatric disorder in the general
  population.

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• Design a study to examine the following null
  hypothesis The prevalence of psychiatric
  morbidity was the same in 1977 and 1985. How will
  you explain any changes in prevalence detected by
  the study

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