Upgrade to remove ads
Ch. 4, Sect. 2, Lesson 2: Epigenetics and Depression
Terms in this set (21)
Biologists recognize _, which is a part of epigenetics.
For a behaviour to occur, genes must be "expressed."
A complex chemical reaction to environmental or physiological changes that allow a gene to "do its job."
Important to know:
_ like stress, exercise or diet, may result in genetic expression, or the lack of it.
Someone may have a gene that could lead to a behaviour, but if the gene isn't expressed, then this behaviour won't occur.
In twin research and studying behaviour, the concordance rate of MZ twins is never 100% because...
genes have to be expressed. MZ twins have the same genes, but may not have been exposed to the same environmental stressors, so the genes aren't expressed.
Concordance rates are higher for MZ than DZ twins because...
twins share some genes, so it's possible both DZ twins share genes related to a behaviour like depression, but not all DZ twins would. Plus, in the DZ twins that do share those genes, some wouldn't be expressed, which accounts for the significantly lower rate of concordance among DZ twins.
_, officially known as Major Depressive Disorder, is considered the common cold of mental health.
Genetic researchers say _ can partly explain depression. Mood disorders tend to run in families, so we can investigate it through _.
genetic predisposition; twin studies
Kendler el al (2006)
showed genetic vulnerability (genetic predisposition)
Twin study of over 42,000 twins from the Swedish national twin registry
Goal: To determine the level of heritability of depression.
Findings: The average concordance rate for...
MZ male twins = 31%
MZ female twins = 44% vs.
DZ male twins = 11%
DZ female twins = 16%
Heritability of depression is estimated to be 38%.
The fact that the concordance rate for MZ twins is far below 100%...
~ indicates depression may be the result of a genetic predisposition, or genetic vulnerability.
~ doesn't contradict the argument that depression is genetically inherited. (It may mean the gene is there, but wasn't expressed b/c both twins didn't experience the same level of stress).
The fact that some of the DZ twins also both had depression is explained by the fact that they do share some of the same genes.
Using DNA markers to identify the gene/s involved in depression.
The Human Genome Project helped us see there are up to _ genetic markers/variations that seem to be correlated with Major Depressive Disorder.
Caspi et al (2003)
Examined the role of the 5-HTT gene in depression. More specifically, the gene plays a role in the serotonin pathways that scientists believe are involved in controlling mood, emotions, aggression, sleep and anxiety.
Hypothesized people who inherit two short versions of the 5-HTT gene are more likely to develop major depression after a stressful life event.
There were 127 DNA samples studied over 25 years from people who were part of a long-term study of mental health. Studied to determine the effect of major life events on mental health.
Findings: Those with...
~ 2 short 5-HTT genes - 80% were diagnosed as depressed after 3 or more negative life events in a year
~ 2 long genes appeared resilient - only 30% developed depression in similar situations.
~ 1 long and 1 short version of the gene had an intermediate risk of depression.
Remember: The study recognizes the importance of environmental stressors in gene expression. Simply inheriting the gene isn't enough to lead to depression.
When evaluating Caspi et al (2003), you should remember...
~ Correlational: The study is correlational, so no cause and effect relationship can be determined.
~ Serotonin Assumption: The study makes an assumption that serotonin causes depression.
~ Self-Reported/Salience: Info. about events was self-reported. Salience of negative life events may play a role in depression (so those who recalled the events easier may have a tendency toward depression, while those who are more resilient may not recall negative life events as easily).
~ Holistic Interaction (Un-Reductionist): The theory acknowledges the interaction between biological and environmental factors in depression, a more holistic approach, not reductionist.
~ Exceptions: Some people didn't have the gene mutation but became depressed anyway, so we can't say gene expression alone can cause depression.
Strengths to genetic arguments for depression
1) Reliable Results: Twin studies have highly reliable results.
2) Genetic Location: We can locate genetic variations using very large sample sizes.
3) Un-Reductionist: Modern research isn't reductionist; it recognizes the interaction of environmental and biological factors in depression.
Limitations to genetic arguments for depression
1) Correlational: Genetic arguments are correlational (they can't establish a cause and effect relationship).
2) Population Validity Problem: Twin studies have a problem with population validity b/c the samples aren't representative of the general population, and they tend to be small.
(It's impossible to isolate variables and separate out the role of environmental factors).
3) Unclear Interaction: (Although genetic markers have been identified,) It isn't clear how (these) genetic markers interact to produce the behaviours associated with depression.
A type of external validity that describes how well the sample can be generalized to a population.
The field of epigenetics studies...
the interaction of genetic inheritence and environmental stimuli. (It looks at the gene - environment interaction and gene expression).
Why is the concordance rate of monozygotous (MZ) twins almost never 100%?
Even though both twins have all the same genes, those genes are not all expressed.
(MZ twins have the same DNA, but don't have the same genetic expression. They aren't a representative sample.)
What assumption does Caspi et al (2003) make about the origin of depression?
That it is caused by a lower rate of serotonin.
(The study isn't of a "depression gene", it's of a serotonin transporter gene, meaning Caspi assumed serotonin is linked to the origin of this disorder, which may be problematic for the validity of the study).
What conclusion did Caspi et al draw from their study of the 5-HHT gene?
Depression was the result of the combination of genetic inheritence and negative life experiences.
Which of the following variables could have an effect on the results (validity) of the study by Caspi et al?
All of the above (The validity of the diagnosis of the participants, individual levels of resilience - how they are able to cope with negative life experiences, and the culture of the sample).
(We have to assume the diagnosis of MDD is valid for all of those who were diagnosed as having the disorder. If people are more resilient, then they may not develop the disorder, which may actually account for the rates being lower than 100%. Culture also plays a role in how we cope with stress and manifest symptoms of mental illness.)
THIS SET IS OFTEN IN FOLDERS WITH...
IB Psychology HL Qualitative Terminologies
Ch. 4, Sect. 2, Lesson 1: Methodology in Genetic R…
Qualitative Research Methods Vocab.
Ch. 4, Sect. 2, Lesson 3: Evolutionary Psychology
YOU MIGHT ALSO LIKE...
Caspi et al. (2003)
Abnormal Psychology - Etiology LAQ
To what extent do biological, cognitive…
OTHER SETS BY THIS CREATOR
Potential exam questions: Treatment of disorders (…
SCLOA Potential Exam Questions
CLOA Potential Exam Questions
OTHER QUIZLET SETS
Chapters 11-Profit Centers
12 week test
chapter 16 labor and birth
World History-Midterm Exam 2017