18-depression.Rmd

# 抑郁

## What is Depression?

### Diagnostic Criteria of Major Depressive Episode

#### At least one of the following three abnormal moods significantly interfered with the person's life:

- Abnormal depressed mood most of the day, nearly every day, for at least two weeks (dysphoria)

- Abnormal loss of all interest and pleasure most of the day, nearly every day, for at least two weeks (anhedonia)

- If 18 or younger, abnormal irritable mood most of the day, nearly every day, for at least two weeks

#### At least five of the following symptoms have been present during the same two week depressed period

- Depressed mood (criterion A, above)
- Loss of all interest and pleasure (criterion B, above)
- Appetite or weight disturbance
- Sleep disturbance
- Agitation or slowing
- Fatigue or loss of energy
- Abnormal inappropriate guilt
- Poor concentration
- Thoughts of death or suicide

### source

- Inheritance
- Stress/Loss

## Prevalence and Incidence of Major Depressive Episode

### Prevalence: the proportion in the population with the illness, e.g., a percentage (burden)

- Define and count the population denominator
- Count cases for the numerator from that defined population
 
### Incidence: the rate at which new cases form in the population, e.g.rate per time (force of morbidity)

- Define the population
- Define the cohort (risk set) who have never had the disorder
- Define the time period for follow-up
- Count the number of person years for the denominator
- Count the number of new cases for the numerator

### variety

- gender: female early
- age: after 50
- lifetime: raise then decrease
- culture: east low, west high

## The Natural History of Major Depressive Disorder

- Prodrome is the period after the disease has begun, before it is diagnosed
  - Dysphoria and suicide have a long prodrome
- Onset is the beginning of the first episode
  - Episodes last several months
- Remission is the end of the symptoms in an episode
- Recovery occurs when a year has passed without another episode
- Recurrence is the start of a later episode after recovery
  - About 50% of all lifetime cases have only one episode
  - About 15% of all lifetime cases are unremitting
  - About 35% of all lifetime cases have a relapsing and remitting course
- Gender Is Associated With Prevalence of Major Depressive Disorder, But Not With Bipolar Disorder
- Gender Affects Incidence But Not Recurrence and Duration

## Major Depressive Disorder and Medical Conditions

- Predictors of Non-Insulin Dependent Diabetes Onset
- Find connection between Depression and certain illness

## Estimating the Burden of Major Depressive Disorder and Medical Conditions

- Estimating the Burden of Disease–Disability Weights
  - Disability weight of 0.0 = healthy person
  - Disability weight of 1.0 = death
  - Disability weight of 0.5 = disability weight indicating the prevention program would have to extend life for two years
- Depression for estimation of disability weight: about 0.35 and top3 around the world

## Does depression look the same across the world?

- Majority of research on mental health has been done in so called ‘high-income countries’
- Our methods/knowledge of mental health originate from research with a minority ‘Western’ (industrialized) population
  -Category fallacy (Kleinman, 1987): Applying a category that makes sense for a particular cultural group in another group, for whom this category may not make sense
- Etic:  
  - Disease perspective
  - International	classification
  - Start with	‘Western’	evidence based treatments	
- Emic:
  - Illness	perspective	
  - Local	terminology	and	ethnopsychology	
  - Build	on locally available treatments	for	mental health	

## Is depression a relevant issue in low- and middle-income countries?

- Despite continued tension between emic and etic approaches, research shows high burden of depression also in low- and middle- income countries.

## What predicts depression in low- and middle-income countries?

- Poverty
  - Out of 115 studies of poverty and common mental disorder:
    79% positive association; 15% no association; 6% negative association
    
    More consistent relation with: education, food security, housing,social class, socioeconomic status, financial stress
- Violence
  - In conflict-affected populations, studies show weighted prevalence of depression: 17.3% (26 studies using random samples and diagnostic interviews)
  - Predictors: potentially traumatic events (OR 1.64); torture (OR 1.48); residency status in asylum seekers (OR 1.30); time since conflict (OR 0.80)

## Basic Concepts of Epidemiology as Applied to Depression

- Definitions of Epidemiology
  - The study of diseases in populations
  - The study of rates (Langmuir)
    Prevalence (burden and demand)
    Incidence (force of morbidity)
  - The study of disease occurrence by time, place, and person (Lilienfeld and Stolley)
- Seven Uses of Epidemiology (Morris)
  - The study the history of health of populations, facilitating projections in to the future
  - To diagnose the health of the community, which facilitates prioritizing health problems
  - To study the working of health services, with a view towards their improvement
  - To estimate individual risks, and how to avoid them, which can be communicated to individuals
  - To identify syndromes
  - To complete the clinical picture of chronic disease, especially as regards natural history
  - To search for causes of health and disease
- Time, Space, and Disease: The Ecological Approach
- Cohort Studies
  - Strengths
    No recall bias
    Estimates incidence
    Estimates Relative Risk
  - Weaknesses 
    Expensive
    Many controls
    Long time
    Attrition bias
- Case Control Studies
  - Strengths
    Requires no hypothesis
    Cases can come from clinics
    Small number of controls
  - Weaknesses
    Biased recall (strength)
    Temporality
    Controls may not match cases (consistency)

## Epidemiology of Depression: Risk Factors

- Inheritance
  - Evidence on Inheritance of Depressive Disorder Selected Family Studies - yes
  - Evidence on Inheritance of Depressive Disorder Selected Twin Studies - yes
  - Evidence on Genome-?wide meta?‐analysis -No!(Manhattan plot)
- Stress and Diathesis
  - Diathesis Stress Model

```{r echo=F}
knitr::include_graphics('http://yufree.github.io/blogcn/figure/DSM.png')
```

- Social Supports
  - Stress increases risk for depressive disorder
  - Social supports are protective from depressive disorder
  - Stress and social supports interact in affecting risk
  - Inherited traits interact with stress in raising risk
  - Low social support is riskier for females
- Work, Family, and Life Stage(forest plot)
  - Work Environment affects risk for depression
  - Life stage affects risk for Depression among Women in London
  - Parenting Stress affects Maternal Mental Health
- Recency of Birth: Are we entering an “age of melancholy?”
  - Cohorts born later have higher risk
    People with depression die sooner
    Older cohorts are less introspective
    More treatment availability leads to better recall
    Older subjects forget more distant episodes
  - We are not entering an “age of melancholy”
  - Appearance of large trends for higher prevalence in later cohorts is probably at least partly an artifact of recall
  - Evidence on trends in rise in incidence is limited, but suggests there has not been a rise in incidence in the past half century
  - There is evidence for a rise in prevalence for women in cohorts born about 1935-1954
  - Women born 1935-1954 entered work and married life in 1955-1974
  - These cohorts of females may have greater chronicity of depression than earlier or later cohorts
  - Trends in social supports and divorce may be connected to trends in chronicity of depression for women

## BARRIERS AND SOLUTIONS

- Large proportions of individuals with major depression do not seek mental health treatment.
- There variations in treatment seeking according to social and demographic factors such as age, sex and racial/ethnic group.
- Barriers include lack of perceived need, negative attitudes towards treatments, stigma and structural barriers.
- Legislative initiatives and antistigma campaigns attempt to reduce these barriers.

## HISTORICAL DEVELOPMENTS & RECENT TRENDS

- Possible reasons for recent trends in treatment of major depression
  - Increased popularity of antidepressant medications among providers and the general population.
  - Fewer side effects of newer antidepressants (practice innovation).
  - Increased treatment of major depression in general medical settings.
  - Aggressive marketing practices by pharmaceutical companies.
  - Greater recognition of “major depression” as an illness.

## QUALITY OF DIAGNOSIS & TREATMENT & INITIATIVES FOR IMPROVEMENT

  - Diagnosis of depression, at least in the US has increased over the past 2-3 decades.
  - Much of the care for depression in community settings is done by primary care and other general medical providers.
  - Many patients with depression, however, are not detected and many individuals who are given the diagnosis do not meet the criteria (false negative and false positive problem).
  - The quality of depression care in the community falls short of standards.
  - Prevention of depression is possible through selective and indicated preventive interventions.