USMLE Biostats 2: Types of Research Studies (Case Control, Cohort, RCT and more!) 

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/ lymed Welcome to LY Med, where I go over everything you need to know for the USMLE STEP 1, with new videos every day.
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This video is going to be on the different types of research. There are two broad categories: experimental (interventional) and observational. There are three types of observational studies: case control, cohort, and cross sectional.
Cohort studies: this is a prospective study, when you take a group of people (cohort) who do not have the disease, but have risk factors. Then you watch them prospectively and see if they develop the disease. You then compare this relative to those who don't have the risk factor: relative risk.
Case control: this is the opposite. This is a retrospective disease, where you get a group of people with the disease and look retrospectively to assess for risk factors. This study helps measure the odds ratio.
Cross sectional studies: this looks at the prevalence of the disease in the present. The group is gathered regardless of exposure or disease.
Some other study types include twin concordance study which looks at the genetic link between disease in twins. Another one is adoption study, which looks at nature vs nuture in children who are adopted to other families.
Our next big category of studies are experimental studies. The best ways to conduct an experimental study is to randomize your groups, having a control group. The gold standard for experimental studies is called a randomized controlled trial for that reason. There are some subtypes of RCTS, including a crossover study where members from one group crossover to the other. Another one is a meta-analysis, which pools common RCT that increase the sample size and power.
Last topic - the stages of an RCT. The first phase is to look at safety, the pharmacokinetics and pharmacodynamics, and side effects. The second phase is on efficacy. This is where most drugs fail. Phase three is whether or not the drug is better. Phase four deals with the longevity of the drug and to monitor it for long term side effects.