Psychology - Depression


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Classification and Diagnosis

Classification: a system that can differentiate between different disorders e.g.        between depression and schizophrenia.

Diagnosis: A clinical judgement that someone is suffering from a disorder and the  diagnosis then leads to treatment.

Two systems: ICD10 and DSM IV-TR.

Originate from 1st classification system devised by Kraeplin, based on an organic view that disorders have:

- A common cause

- Require similar treatment

- Progress similarly if left untreated (have a similar outcome/prognosis)

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Classification of Depression

Classified as a mood disorder, this can affect a person's perception, thinking and behaviour.

Unipolar disorder / Major depression:                                                                             - An episode of depression that occurs suddenly                                                           - Can be reactive (caused by external factors e.g. death of a loved one)                       - Can be endogenous (caused by internal factors e.g. neurological factors)                   - Prevalence: at least a 5% lifetime risk ; appears cross-culturally ; diagnosed twice as often in women.

Bipolar disorder / Manic depression:                                                                               - An alteration between mood extremes, mania and depression                                    - Change in mood often occurs in regular cycle of days/weeks                                      - Episodes of mania involve over-activity, rapid speech and feeling extremely happy/agitated                                                                                                                 - Prevalence: about a 1% lifetime risk.

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Clinical characteristics of depression


hysical/behavioural symptoms include:                                                                        - Sleep disturbances e.g. insomnia / hypersomnia                                                        - Changes in appetite with weight gain / loss                                                                  - Pain e.g. headaches / joint ache / muscle ache

Affective / emotional symptoms:                                                                                     - Extreme feelings of sadness, hopelessness and despair                                             - Diurnal mood variation - changes in mood throughout the day                                     - Andehonia - no longer enjoying activities or hobbies that used to be pleasurable

Cognitivesymptoms:                                                                                                       - Experiencing persistent negative beliefs about themselves / their abilities                   - Possible suicidal thoughts   - Slower thought processes - difficulty concentrating and making decisions                                                                          Social / motivational symptoms:   - Lack of activity - social withdrawal and loss of sex drive

DSMIV: at least 5 symptoms every day for at least 2 weeks = unipolar

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Classification given to those who:

- suffer chronic mild depression over a period of not less than 2 years

- a depressed mood and other symptoms of mild depression are suffered for most     of the day, on more days than not, without a break, for more than 2 months in a 2   year period

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Aim of classification of depression

To be useful they must:

- provide a comprehensive set of descriptive accounts that includes all types of         abnormal behaviour

- only include classificatory categories that are mutually exclusive i.e. the                   boundaries between different categories must be clearly drawn out so that it is       obvious that an individual's symptoms fit into one particular categoy.

- must be reliable

- must be valid

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Definition of reliability and validity in relation

Reliability: relates to how consistent measures are.

Inter-rater reliability: to what extent does the ICD or DSM result in the same label if          the patient is rated separately by 2 independent assessors.

Test-retest reliability: whether the result is likely to be the same if repeated on two    separate occasions.

Validity: refers to the extent to which the ICD and DSM are true measurements of         an actual disorder.

Different types of validity which relate to classification include:

Descriptive validity: how similar individuals diagnosed with the same disorder are.

Aetiological validity: how similar the cause is for each sufferer.

Predictive validity: how useful the diagnostic categories are for predicting the right       treatment.

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Research into reliability of classification

Keller: used DSMIV both for major depressive disorder and dysthymia.      524 patients interviewed using DSM criteria.        Interviewed 6 months later to establish test-retest reliability.              Results showed that inter-rater reliability was fair to good.        At 6 months, test retest reliability: fair for dysthymia ; poor to fair for unipolar

Zanharini: Inter-rater reliability of 0.80 for major depression     Test-retest correlation after 1 week was 0.61      Shows that reliability deteriorates rapidly.

Comments:   - Keller suggested: number of possible reasons why DSM might lack reliability - for diagnosis to be made, a minimum of 5/9 symptoms must be present. When there is one item disagreement, could mean the difference between diagnosis of major depression and a less serious illness.

- Large sample of patients = results likely to be more representative of general         population of depressed patients.   - Longitudinal study = may be dropout = biased sample (co-operative participants)

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Research into validity of classification

van Weel-Baumgarten: GP diagnosis of depression may be less objective than      other specialists as they are basing their diagnosis on       previous knowledge of the patient rather than symptoms      that are actually present.


- Very difficult to study validity of diagnosis as diagnosis is based on interview method.

- It could be that individuals react differently to a stranger than to a familiar GP.

- Specialists may be biased - are actively looking for symptoms of depression.

- Patients may be having a particularly bad day when seeing the specialist and         interviewer effects (encouraging individuals to talk more about their feelings)           could bias the outcome.

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Evaluation of general reliability and validity of

Both the ICD and DSM have problems with reliability and validity.

It is claimed that the ICD is 'shot through with Eurocentric bias'  

i.e. diagnosis is affected by white Western values.

Our views of normality and abnormality are cuturally biased.

Approaches and treatments vary between cultures.

In Africa, depression is called 'ants in the brain'.

The systems are undergoing research  - The ICD was revised in 2000

        - A new version of DSM is planned for 2011

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Arguments for the classification systems in diagno

Enable disorders to be universally recognised and allow health professionals  to communicate.

Aim to help individuals - might feel relieved at being given a diagnosis and have the prospect of treatment.

Try and find the cause of disorder and the classification can lead to successful treatment

e.g. depression can be linked to high levels of the hormone cortisol and high levels of the neurotransmitter serotonin. Drugs can be used to successfully treat depression by addressing physiological aspects of the disorder.

SImilarities between the ICD and DSM suggest there is a reliable way of assessing mental disorder.

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Arguments against the classification system - Prob

Diagnosis of a disease = with varifiable pathology e.g. blood tests/x-rays etc.

With mental disorders, the main diagnosis is based on observation of behaviour in an interview so is based on judgements of the clinician which are subjective, not objective.

- Can be argued that classification of mental disorders is something we have imposed artificially on behaviour in order to help us understand it - in reality it may not be valid.

- Symptoms of depression (posture/facial expressions etc) are monitored during an interview with a psychiatrist/doctor who is looking for symptoms of a disorder and so may be biased in their observations.

- Patients may react in a certain way - give a biased salf-report.

- Even when other techniques e.g. Beck Depression Inventory there are problems with validity/reliability as outcomes are based on subjective reports and biased analyses.

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Research relating to problems of validity of asses

Beck - Test-retest reliability studied using responses of 26 outpatients tested               at therapy sessions 1 week apart.       Correlation of 0.93 indicating a significant level of test-retest reliability.

Visser - assessed 92 patients with Parkinson's disease for depression using DSM      and Beck Depression Inventory.          In part 2 of study 60 patients completed the BDI again as part of postal                survey, producing a test-retest correlation of 0.88, suggesting that the                BDI was a reliable measure of severity of depressive symptoms.


Beck's sample was small - cannot be generalised to all depressed patients.   Period between test and re-test was very short, participants could have remembered answers.   Visser's research was age biased - Parkinson's patients are generally older so will not be representative of younger depressed patients.   Postal survey = relatively cheap and easy was to collect data.

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Problems relating to reliability of assessment

People showing same symptoms don't always get same diagnosis because:

- Classification of symptoms overlap and some categories are questioned - depression is present in many other disorders - 'co-morbidity' causes a problem for reliability of diagnosis.

- Distinctions between different types of depression are not clear - 10% of people diagnosed with unipolar go on to develop bipolar.

- Patients are given a series of different diagnoses and many are misdiagnosed therefore receive the wrong treatment - could be damaging.

- Many GPs don't recognise the symptoms of depression - Goldberg and Huxley found half of people who go to GP have depressive symptoms and these are not recognised.

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General issues of reliability and validity of diag

- Gender affects diagnosis rates - females = more likely to be diagnosed with depression. May be due to biological differences or life stress differences rather than bias in expectation of clinician. May be a problem of expectation due to gender stereotyping e.g. women may be expected to be more emotional and unstable. Men may be less likely to admit to having symptoms.

- Cultural values affect diagnosis and classification. Other cultures deal with disorders in different ways e.g. China - depression is seen as a problem with living rather than a medical problem. Individuals seek help from family not doctor.

- Cultural differences supported by research: Karasz described depressive symptoms to 2 diverse cultural groups in New York - S. Asians and Eu. Americans. S. Asians identified the problem in social and moral terms. needing self management and non-professional help. Eu. Americans emphasised biological explanations of the symptoms, inc. hormonal imbalances and neurological problems.

Comments: Useful - natural expt - naturally occuring groups. Groups may not be representative of culture as may have been westernised.

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General issues of diagnosis

- Many disorders do not result from a medical problem e.g. depression can be caused by events in individual's life e.g. bereavement so it doesn't make sense to diagnose it as a medical disorder.

- The end result of diagnosis/classification also has ethical considerations due to problem of labeling and stigma as can have a negative impact on the life of the individual. The label may also become a self-fulfilling prophecy ; the individual may give up and feel that they have lost their identity.

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Biological explanation of depression

That which is psychological is first physiological - all thoughts, feelings are behaviours ultimately have a physical or biological cause.

Psychology should therefore investigate genetic links, structure of the brain (neuroanatomy), nervous system, endocrine system (hormones), and neurochemistry (e.g. neurotransmitters).

Reasons why depression has been linked to biological factors:

- Symptoms usually include physical changes.

- Depression runs in families.

- Drugs are helpful in offering relief.

- Certain drugs, which are given in other treatments, may induce symptoms of           depression.

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Genetic factors: AO1

- Being biologically related to someone seems to increase their chance of developing depression.                                           - Children of depressed parents are much more likely to be depressed than their peers. Could be due to environment as families inevitably share same env.   - Recent genetic research looked into influence of particular genes and how these interact with the environment.   - Serotonin transported gene which is responsible for producing serotonin in the brain. Gene comes in various forms due to variations in the length of its 2 strands. Long has been linked to depression.    Comment: Research into genetics uses the scientific method, based on precise and replicable procedures which are replicable. Precise questions can be asked.

Kendler - found that women who were genetically predisposed to depression (had a twin with depression) were far more likely to develop depression when faced with -ve life events - which has been linked to the stress-diathesis model where both the genetic predisposition 

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