Psychology

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Depression

Diagnosis and classification of depression

Depression is classified under the DSM as a mood disorder. Most depressed individuals will suffer from only one type of depression (unipolar), whereas others may experience states of mania that alternate with depression (bipolar). Comer (2001) claimed depression is ‘a low, sad state marked by significant levels of sadness, lack of energy, low self-worth, guilt or related symptoms’.

Diagnosis requires the presence of 5 of the following symptoms (which must include either depressed mood or loss of interest and pleasure). These symptoms must cause significant distress or impairment in general functioning, and must not be accounted for by bereavement.

* Sad, depressed mood (e.g. feeling sad or appearing tearful). * Loss of interest and pleasure in usual activities.
* Difficulties in sleeping (insomnia or hypersomnia).
* Shift in activity levels (lethargic or agitated).
* Poor appetite or increased appetite.
* Negative self-concept, feelings of worthlessness and guilt. * Difficulty in concentrating.
* Recurrent thoughts of death and/or suicide.

Reliability of diagnosis

The consistency of a measuring instrument such as a questionnaire or scale to assess whether two independent assessors give similar diagnoses (inter-rater reliability) or whether tests used to deliver diagnoses are consistent over time (test re-test reliability).

Inter-rater reliability:

Low levels of inter-rater reliability related to any classification procedure suggest it might lead to faulty diagnosis and inappropriate treatment. Lobbestael et al (2011) assessed inter-rater reliability of the structured clinical interview for assessments of major clinical depressive disorder in a mix of patient/ non-patient controls. Results found moderate agreement with inter-rater coefficient of 0.66.

Test-retest reliability:

This is a major goal in the new version of DSM. Current measurement scales = BDI (Beck Depression Inventory).

Evaluation of diagnosis criteria of the DSM:

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The DSM is constantly changing with the developments of technology and science. This makes the research and content more valid and reliable, as up-to-date information is constantly being used. -
Keller et al (1995) carried out a study to explore the reliability of the classification of depression using 524 outpatients. They were interviewed using the DSM criteria then re-interviewed 6 months later. The inter-rater reliability were fair to good and the test re-test reliability was poor to fair.

According to Keller (1995) the reason for low reliability was due to the high requirements of the diagnosis. One item difference can make the difference between a diagnosis of MDD and a less serious diagnosis.

It can sometimes be hard to determine each type of depression and their symptoms. GP’s may also give invalid diagnosis accounts based on previous knowledge of the patient. Tiller (2001) found only a ¼ of doctors could remember all 9 symptoms= unreliable.

Synoptic; observer-bias

Subjectivity of diagnosis- judging whether patients have any given symptom is subjective because they cannot be measured. For example, loss of pleasure in usual activities is a symptom of MDD, but how much loss of pleasure is needed to qualify?

Beck Depression Inventory (BDI)

What is the BDI?

A self-report questionnaire designed to measure the severity of symptoms in individuals with depression. Each question assesses a specific symptom (items 1-14 measure psychological symptoms, while items 15-21 measure physical symptoms). Every item is accompanied by four alternative responses, graded for severity from 0-3.

How do you test severity?

The sum of the BDI items indicated the severity of depression. For the general population anything over 21 indicated depression, for those who have been diagnosed a score of 0-9 represents minimal depressive symptoms compared to a score of 30...
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