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PSYCHIATRIC EPIDEMIOLOGY

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					 PSYCHIATRIC
EPIDEMIOLOGY
                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
            Uses of Epidemiology


1. Completing the clinical picture
2. Community Diagnosis
3. Secular changes in incidence
4. Identification of Risk Factors/Protective
   Factors/Prevention
5. Delineation of syndromes
6. Planning services
          Epidemiology Terms
• Rates and Ratios
• Prevalence
  –   Point
  –   Period
  –   Lifetime
  –   Treated and untreated
• Inception (Incidence)
        Prevalence and Inception Rates


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


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

• Cross-Sectional Studies
• Longitudinal Studies
  – Prospective
  – Retrospective
• Case-Control Studies
• Case Register Studies
Any Epidemiological study can be
  Observational or Experimental
    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
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
                    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
                   Instruments
• Questionnaires
   –   GHQ
   –   HAD
   –   Beck’s inventories
   –   Symptom checklists
• Rating scales
   – Hamilton’ Depression Scale
   – Bech Raphaelson Mania Rating Scale
   – MIMS?
   Establishing a causal link between event and
                     disorder

                           Case
                        Yes          No

                 Yes       a          b
Exposed
                  No      c           d
               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)
          Structured Interviews
•   Can be applied by trained lay persons
•   Statements and wording pre-set
•   Standard
•   Examples:
    – DIS
    – CIDI
   Semi-Structured interviews
• PSE
• SCAN
• CIS
        Issues of Reliability and Validity


Reliability
Interrater agreement
Test-retest
Validity
  Construct
  Content
  Correlation with gold standard
     Sensitivity and Specificity
•                  Cases by full psychiatric
                           assessment
                       Yes             No
Cases by screening Yes a(TP)          b(FP)
Test
                   No c(FN)           d(TN)
  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
   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
   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
       Stirling County: Alexander Leighton


• 20,000 rural persons ,non-clinicians,
  structured interview, later psychiatrist rating
• 24% had notable impairment, and 20%
  needed psychiatric attention
• Women>men, morbidity increases with age
  and poverty
     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
    Psychiatric Morbidity in Upper Egypt                         (n=5291)

  Total caseness                                                            18.2%
Case in treatment       0.4%
Case in remission           2.1%
            Case                                8.8%
      Likely case                           6.9%
      Subclinical                                                         17.4%

                    0              5               10            15              20
                        Subclinical         Likely case         Case
                        Case in remission   Case in treatment   Total caseness
     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
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
Design an epidemiological study
that could determine the prevalence
and demographic correlates of
psychiatric disorder in the general
population.
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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