This shows that the old idea of diathesis as biological and stress as psychological is too simple.
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diathesis-stress model of psychological disorders

Loss of Energy

0. I have as much energy as ever

1. I have less energy than I used to have

2. I don’t have enough energy to do very much

3. I don’t have enough energy to do anything

As you can see, each item is rated 0 to 3 and a cumulative total gives an indication of severity of depression.

0–9 indicates that a person is not depressed,

10–18 indicates mild-moderate depression,

19–29 indicates moderate-severe depression and

30–63 indicates severe depression.

Reliability of BDI
Beck et al (1996) gave the test to 26 outpatients during two therapy sessions one week apart. The test-retest concordance was a very high 0.93.

The test is also high on split-test reliability (0.85). Most studies carried out on reliability find that the BDI is a reliable test of depressive severity.

Validity of BDI
The BDI has concurrent validity in that it tends to agree with other measures of depression.

It is also high on construct validity. An obvious way to judge validity of a test is to observe the person in real life situations. If the person scores as suffering severe depression then this should be observable in their behaviour.

BDI-II was introduced specifically to bring it into line with the DSM-IV diagnosis. BDI-II is seen as having higher content validity than its predecessor BDI-1A.

Note: the BDI is not intended to diagnose depression. It was designed by Beck to measure the severity of depression in patients aged 13 and over, who had already been psychiatrically diagnosed with depression. The danger of using it as a diagnostic tool is that the characteristics it is measuring may well be the symptoms of other unknown disorders.

A combination of genetic evidence and discussion of the permissive amine theory is needed here. Remember too that these are not mutually exclusive. A decreased sensitivity to a particular neurotransmitter is likely to be caused by a genetic abnormality!

Genetic explanation
All the usual points need to be borne in mind and spelt out to the examiner. Clearly you will want to mention trends within families, twin studies (MZ and DZ), adoption studies and gene research. These then need to be evaluated in terms of environmental influences and the extent to which they can explain patterns such as sex differences.

Family patterns and studies
Depression does tend to ‘run in families.’ Gershon (1990) found that the incidence of depression is up to three times higher in families with a history of the disorder than it is within the general population as a whole. Others have put this figure even higher. Weissman (1987) looked at the prevalence of affective disorders in general and found that family members with first degree relatives (parent, sibling) with a mood disorder were up to ten times more likely to suffer from one too.

Twin studies
We’ll distinguish here between unipolar and bipolar disorders:

Unipolar or major depression

Allen (1976) reported the following concordance rates:

Suggesting a genetic component to explain the difference between the two.

Bipolar (or manic) depression

It is worth mentioning that different studies have produced varying percentage figures but the overall trend is usually the same.

You must point out however the shortcomings of twin research:

Fowles Department of Psychology, University of Iowa, sistent with the diathesis-stress model.
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systems approach to psychological disorders.

Many models of generally suggest that all people have some level of vulnerability towards certain mental disorders, but posit a large range of individual differences in the point at which a person will develop a certain disorder. For example, an individual with personality traits that tend to promote relationships such as and may engender strong social support, which may later serve as a protective factor when experiencing stressors or losses that may delay or prevent the development of depression. Conversely, an individual who finds it difficult to develop and maintain supportive relationships may be more vulnerable to developing depression following a job loss because they do not have protective social support. An individual’s threshold is determined by the interaction of diatheses and stress.

diathesis synonyms, diathesis pronunciation, High stress independently predicts peptic ulcers.
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The diathesis–stress model asserts that if the combination of the predisposition and the stress exceeds a threshold, the person will develop a .

DIATHESIS-STRESS MODEL OF DEPRESSION 3 A Test of the Diathesis­Stress Model of Depression in International Students in Spain Depression is a major.
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Diathesis–stress model - Wikipedia

Early and severe enough trauma such as child abuse can seriously affect many aspects of brain development

For example, the
hypothalamic-pituitary-adrenal (HPA) system
can become over-active making the person more vulnerable to later stress
The End!
The Interactionist Approach
The interactionist approach (also known as the
Bio-Social Approach
) recognises that biological, psychological and societal factors are all involved in the development of schizophrenia

Biological factors include:
- genetic vulnerability
- neurochemical/neurological abnormalities

Psychological factors include:
- stress resulting from, for example, life events and daily
hassles such as poor quality interactions in the family
Evidence for the role of vulnerability and triggers:
-Tienari et al (2004) investigated the combination of genetic vulnerability and parenting styles (the trigger)

- Children adopted from 19,000 Finnish mothers with schizophrenia were followed up

- Adoptive parents were assessed for child-rearing style and the rates of schizophrenia were compared to those in a control group of adoptees without any genetic risk

- A child rearing style characterised by high levels of criticism and conflict and low levels of empathy was seen to be associated with developing schizophrenia but only for the children with high genetic risk (not those in the control group)

- This suggests that both genetic vulnerability and family-related stress are important in the development of schizophrenia (genetically vulnerable children are more sensitive to parenting behaviour)

- This is very strong support for the importance of adopting an interactionist approach to schizophrenia
The Interactionist Approach
To Schizophrenia

Modern Understanding of Stress:
Original model
- stress was seen as psychological (in partic, related to parenting)

Modern definition of stress
(in relation to diathesis-stress model) - anything that could trigger schizophrenia (Houston et al, 2008)

Recent research
- cannabis use as a trigger of schizophrenia:
cannabis is a stressor as it increases the risk of schizophrenia by up to 7 times

This is probably because cannabis interferes with the dopamine system however, most people don't develop schizophrenia after smoking cannabis so it seems there also needs to be one or more vulnerability factors
Treatment According to the Interactionist Model:
Interactionist model acknowledges both biological and psychological factors in schizophrenia so therefore it is compatible with both biological and psychological treatments

The model is particularly associated with combining antipsychotic medication with psychological therapies (partic CBT)

Turkington et al (2006)
- possible to believe in biological causes of schizophrenia and still use CBT to relieve psychological symptoms

However, this requires adopting an interactionist model; it is not possible to use a purely biological approach and tell patients that their condition is purely biological and then treat them with CBT

- standard practice to treat with a combination of antipsychotics and CBT

- a greater history of conflict between biological and psychological models of schizophrenia so they've been slower to adopt the interactionist approach therefore medication without psychological treatment in more common

Unusual to treat schizophrenia with just psychological therapies.