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Etiologies of Major Depressive Disorder (Description- (To be used to…

- - - - Feelings of guilt or sadness, lack of enjoyment or pleasure in familiar activities and company
- - - - Aim-To investigate genetic factors in depression by looking at the concordance rates for depression in monozygotic and dizygotic twins
      - Sample- 42161 twins, some monozygotic (same DNA) and some dizygotic (different DNA)
      - Results
        
        Female
        
        Monozygotic: 44% concordance
        
        Dizygotic: 16%
        
        Male
        
        Monozygotic: 31%
        
        Dizygotic: 11%
      - Conclusions
        
        Women may be genetically more predisposed to depression
        
        Genetic factors may predispose people to depression
        
        As the concordance rate for MZ twins is far below 100%, the relationship may only be one of increased vulnerability, and that environmental stimulus is required to cause depression.
      - Strengths
        
        Very large sample size which increases external validity
        
        The results mirror what is perceived by society: that women have a higher rate of depression than men
      - Weaknesses
        
        no specific genes are identified, isolating genes is important for gaining a better understanding
        
        We cannot know if the twins had the same genes but were not expressed
        
        Research into gender differences in depression argue that women are subjected to more environmental stressors which could account for the greater concordance rate
    - - Aim- To investigate the role of the 5HTT gene on depression. This gene is responsible for the transport of serotonin across the synapse.
      - Sample- New Zealanders
      - Procedure- Capsi classified the sample into groups, based on whether they had two long 5HTT alleles, one long and one short, or two short alleles.They were also asked to fill in a stressful life events survey. Their mental health was monitored over the following five years.
      - Results- Participants who had two short alleles and had also experienced more than 3 stressful life events were more likely to experience depression
      - Conclusions Genetics may have an influence on depression, however, they need to be expressed by environmental stressors
      - Strengths
        
        Large sample size
        
        Identifies a genetic variation
        
        Longitudinal, holistic view of participants- evaluates interaction between environment and genetic
      - Weaknesses
        
        Based on the assumption that serotonin plays a role in causing depression
        
        Some argue that depression causes low serotonin levels rather than vice-versa
        
        Symptoms were self-reported- participants were not actually diagnosed- reducing validity
        
        Low reliability due to lack of replications which found similar results
    - - All genetic research is correlational in nature- no cause and effect can be estalished
      - In order for psychologists to understand the origin of the disorder, the must understand the physiological changes caused by the genes and their relationship to depression
      - It is impossible to isolate biological factors. Our genes interact with the environment
      - Cognitive factors may act as mediating factors for depression
      - Could be seen as reductionist. Despite being helpful in providing effective drug treatment, it does not explain the wide range of symptoms.
      - Some symptoms vary in different cultures e.g. back pain in Chinese people
    - - Genetic arguments show great promise for helping to explain depression
      - However, as there are many genes thought to be involved in affecting depression, it is difficult to know how all of these genes interact
      - Genetic markers may be useful in the study of genes
- - - - Strengths
        
        Shows support for Beck's model
      - Weakness
        
        Highly artificial task so low ecological validity
        
        The sample with depression were already diagnosed, so it is not possible to say that these thoughts caused their depression
        
        It could be that memory bias is a result of depression
        
        A limitation of Beck's theory is that it is unclear whether thinking patterns are a cause or an effect of depression. Consequently, prospective research has been done
  - - - Strengths
        
        The strong trend suggests that thinking styles may play a large role in depression
        
        Provides prospective research
      - Weaknesses
        
        The research is correlational so no cause and effect can be established
        
        It does not consider daily stress
        
        It does not consider the role of genetics
- - - - Vulnerability factors- These factors increase the likelihood of depression in combination with stressful life events, e.g. loss of your mother before age 11, the lack of a confiding relationship
      - Protective factors- These are factors which reduce the likelihood of depression, e.g. a strong sense of community or a strong relationship with a family member
      - Provoking agents- This is acute and ongoing daily stress
      - The model suggests that depression is more likely when one's vulnerability factors are greater than one's protective factors
    - - Aim- Investigate the role of environmental factors on the onset of depression in women
      - Sample- 458 women in London
      - Procedure- Participants answered a survey about biographical information and difficulties that they have faced
      - Results- 8% of all women had developed depression in the previous year. Almost 90% of them had experienced an adverse life event in the previous year. This is compared to 30% of people who had not been diagnosed with depression
      - Evaluation
        
        Strengths
        
        This research was one of the first to suggest that the prevalence rate of depression in women is higher due to greater amounts of risk factors
        
        Weaknesses
        
        There may be cultural biases in the research. London has a very individualistic culture where people are expected to keep problems private and are less likely to reach out for help. This may mean the research is not applicable in other cultures
        
        The research does not consider cognitive processes as a mediating factor for depression
        
        There can be weaknesses when measuring stress. Stress is a subjective experience meaning it can have different effects on different people. Making it difficult to measure and to make conclusions from
        
        There is less consideration for daily stressors as a source of depression
      - Conclusion- The researchers argued that adverse life experiences are risk factors for depression. This study supports the vulnerability model by suggesting that life experiences may interact with genetic predisposition for depression
    - - Aim- To investigate the role of protective factors in the onset of depression in gay men diagnosed with HIV
      - Sample- Gay men diagnosed with HIV
      - Results- The men who had been rejected by friends and family were more likely to develop depression and have a faster onset of AIDS
      - Evaluation
        
        Weaknesses
        
        This research is correlation, it may not be the lack of family support that causes depression
        
        It is hard to control variable which means a conclusion about cause and effect cannot be made
    - - The greatest limitation of this approach is that we cannot isolate biological or cognitive factors
      - Vulnerability models could help to prevent the onset of depression by providing those at risk with more protective factors
      - Changes in prevalence rates can be explained by the changeability of risk and protective factors. This is something the biological approach cannot do.
      - The vulnerability model is only useful when considered alongside biological etiologies
    - - AIm- To investigate the affect of hand holding on the levels of stress experienced during a threatening situation
      - Sample- A sample of married women
      - Procedure- The women were threatened with an electric shock. They were shown certain images which were an indication that they were going to be shocked. The women were in an fMRI machine during the experiment. They either held their husband's hand, the hand of an anonymous male researcher or did not hold anyone's hand and lowest when not holding any hand.
      - Results- The brain's threat response was lowest when holding their husband's hand. There was also a negative correlation between marital satisfaction and stress response.
      - Link- This study suggests that social support could be a protective factor against depression
      - Evaluation
        
        Weaknesses
        
        Although social support is a social factor, there may be physiological changes in the brain as a result of physical contact. For example, a neurotransmitter or hormone may be released which could act as a protective factor for depression
- - - - The data is self-reported. There is no official diagnosis of the depressed women in the study
      - This is a general weakness of prevalence data, It may not be representative of the true proportion of the population which has the disorder. Hospital records may not be valid as not everyone seeks treatment.
      - The interview method may cause there to be a higher prevalence rate than there actually is, due to people experiencing symptoms without actually having depression. A lack of formal diagnosis enables this potential inflation.
      - As there are validity and reliability issues with diagnosis, there may be the same issues when it comes to prevalence rates
  - - - Becker used two groups of girls so she could focus on one age bracket, however this prevents us from ruling out the affect of individual differences on the results.
      - Symptoms are self-reported and no formal diagnosis has been made which weakens the strength of conclusions. Triangulation of data with hospital records would be the only way to verify that an increase has occurred.
      - Although the natural setting of the experiment is a strength, it means that the study cannot be replicated, which reduces the reliability of the research.