topic 3 (genetic methods and mental health problems)

Question 1

what is a candidate gene?

Answer 1

any single gene thought to be likely to cause a disease

this is through a priori selection- so hypothesis driven based on previous findings or established biological pathways

Question 2

what are critiques of candidate gene studies?

Answer 2

a priori selection doesnt allow for novel gene discovery

they only tend to show a very small effect size on mental health so they cannot tell us much about mental health

studies tend to be small and not replicable

Question 3

what is a genome wide association study?

Answer 3

• a study of a genome wide set of genetic variants (500,000+) , examining how many genetic variants are associated with a mental or physical health problem
• they compare the DNA of those who have the disorder to those who do not have the disorder
• consortiums where researchers combine studies can allow samples of over 1,000,00

Question 4

what are critiques of genome wide association studies?

Answer 4

• most studies have been done in WEIRD samples so generalisability is not know
• in consortium studies different measures may have been used between studies

Question 5

describe polygenic risk scores

Answer 5

polygenic risk score= a genetic score based on the restults of a GWAS, which can combine thousands of genes which associate with an outcome

the higher the score the higher the genetic risk

these genes each have very small individual effect sizes but when combined the effect size increases

these scores can be created by smaller independent studies but because they are informed by larger independent study they can replicate better

Question 6

what does reserach say about how much variance in depression polygenic risk scores can account for?

Answer 6

one study showed that polygenic risk scores only account for 3.2% of the variance in depression