In the early, desperate months of the pandemic, some medical centers published the results of studies that involved providing a potentially effective treatme
In the early, desperate months of the pandemic, some medical centers published the results of studies that involved providing a potentially effective treatment to a series of patients. There was no randomization and no control group involved. Often different facilities obtained different results and subsequent randomized controlled trials failed to find the treatment to be effective.
Was it right to publish the results of such observational studies?
How was the general public affected by popular media coverage of these studies?
Did the coverage create confusion or mistrust?
100 words
Research Methods in Health Psychology
Correlational Studies
Correlational studies indicate the degree of relationship between two variables, such as the number of stressful life events and the risk of heart attack.
This approach is one type of descriptive research.
In correlational studies, the relationship between two variables is expressed in terms of correlation coefficients. Coefficients range from -1.00 to +1.00, with numbers closer to ±1.00 indicating stronger relationships. Attributions of cause and effect are not possible from correlational studies
Example of a Correlational Study
Marital separation and divorce are associated with increased risk for early death, and the magnitude of this association rivals that of many well-established public health factors. In the case of divorce, however, the mechanisms explaining precisely why and how some people are at risk for early death remain unclear. This paper reviews what is known about the association between divorce and risk for all-cause mortality, then discusses four emerging themes: the biological intermediaries linking divorce to pathophysiology and disease onset, moving beyond the statistical mean, focusing research on the diathesis-stress model, and studying how opportunity foreclosures may place people on a trajectory toward poor distal health outcomes.
Cross-Sectional and Longitudinal Studies
Cross-sectional studies are conducted at one point in time and compare people of different ages.
Longitudinal studies follow participants over an extended period of time.
Cross-sectional studies can show differences between groups, but longitudinal studies can reveal developmental trends.
Disadvantage of taking along time and being expensive.
Example of a Longitudinal Study
The National Longitudinal Study of Adolescent Health (Add Health) is a longitudinal study of a nationally representative sample of adolescents in grades 7-12 in the United States during the 1994-95 school year. The Add Health cohort has been followed into young adulthood with four in-home interviews, the most recent in 2008, when the sample was aged 24-32*. Add Health combines longitudinal survey data on respondents’ social, economic, psychological and physical well-being with contextual data on the family, neighborhood, community, school, friendships, peer groups, and romantic relationships, providing unique opportunities to study how social environments and behaviors in adolescence are linked to health and achievement outcomes in young adulthood.
Experimental Designs
Experimental designs can determine cause and effect relationships by manipulating an independent variable and observing the effect on a dependent variable, for example, comparing an experimental group on a low-fat diet (treatment group) to participants who maintain their regular diet (control group) and then measuring the development of cardiovascular disease (the dependent variable) in the two groups. Well-controlled experimental designs give scientists their best method to determine causation.
Ex Post Facto Designs
Ex post facto designs are similar to experimental designs in that both use contrasting groups, but these designs do not include manipulation of independent variables. Instead, groups of participants differing on some subject variable (or participant variable) are contrasted to determine differences in the dependent variable. For example, contrasting people with varying levels of obesity to determine in food choices is an ex post facto study. The finding that heavier individuals express food preferences that differ from those of less obese individuals does not demonstrate that obesity is causally related to food preferences because ex post facto studies do not manipulate an independent variable or control for other factors.
Observational Methods
Observational methods parallel correlation studies in psychology. The two types of observational methods are retrospective and prospective. Prospective studies are longitudinal designs that follow the forward development of a group of people starting an experience together. Retrospective studies begin with a group of people already experiencing a disease and then look for characteristics of these people that are different from those of people who do not have that disease. Retrospective studies are also called case-control studies because cases (people with a disease) are compared with controls (people not affected).
Case Studies
In depth analysis of one individual
Type of single-subject research design
Advantage is a more complete analysis of the individual
Disadvantage is that it can magnify sampling errors
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Sampling error problem – One purpose of any scientific investigation is to learn something that can be generalized to other participants, other people, or even to an entire population. Case studies may generate finds that are only relevant to that particular individual and so cannot help inform us about factors or processes that are also apply to other individuals or populations.
Randomized, Controlled Trials
Randomized, controlled trials are equivalent to experiments in psychology. Clinical trials are randomized, controlled trials designed to test the effectiveness of a drug or treatment. Researchers assign participants to groups randomly to control for self-selection. Randomized, placebo-controlled double-blind designs are often considered the zenith of research design, but comparative research indicates that observational studies can yield similarly valid results.
Natural Experiments
Natural experiments are similar to ex post facto studies in psychology; both involve the selection rather than the manipulation of a variable. Natural experiments can be conducted when two similar groups of people naturally divide themselves into those exposed and those not exposed to a pathogen.
Meta-analysis
The statistical technique of meta-analysis allows researchers to evaluate many research studies on the same topic, even if the research methods differed. In addition, meta-analysis provides an index of the size of the effect, which allows researchers to gauge the importance of the effect.
The Role of Psychometrics in Research
Health psychologists, like other scientists, use measuring instruments to test their hypotheses and to build their theories. To be useful, measuring devices must be both reliable (consistent) and valid (accurate).
Research Methods in Epidemiology
Epidemiology is a branch of medicine that investigates factors contributing to the occurrence of a disease in a particular population.
Epidemiology evolved into a scientific discipline during the 19th century and played an important role in the fight against infectious diseases.
Today, epidemiologists also study factors associated with chronic illness, including its prevalence and incidence.
Goals of Epidemiology
Establish diagnosis
Identify specific agent
Describe according to person, place and time
Identify source of agent
Identify mode of transmission
Identify susceptible populations
John Snow (1813-1858)
Father of epidemiology
Careful mapping of cholera cases in East London during cholera epidemic of 1854
Traced source to a single well on Broad Street that had been contaminated by sewage
Typhoid Mary and the Start of Epidemiology
Mary Mallon, a cook responsible for most famous outbreaks of carrier-borne disease in medical history
Recognized as carrier during 1904 N.Y. typhoid fever epidemic
When source of disease was traced, Mary had disappeared only to resurface in 1907 when more cases occurred
Again Mary fled, but authorities led by George Soper, caught her and had her quarantined on an island
In 1910 the health department released her on condition that she never accept employment involving the handling of food
Four years later, Soper began looking for Mary again when two new epidemics broke out; Mary had worked as a cook at both places
She was found and returned to North Brother Island, where she remained the rest of her life until a paralytic stroke in 1932 led to her slow death, six years later
Prevalence and Incidence
Prevalence is the proportion of the population affected by a particular disease at a particular time, whereas incidence is the number of new cases of a disease during a particular time, usually one year. Research methods used in epidemiology are similar to those employed by psychologists. Epidemiology research falls into three broad areas: observational methods, natural experiments, and experimental investigations.
Terminology
Endemic: a disease or pathogen present or usually prevalent in a given population or geographic region at all times
Hyperendemic: equally endemic in all age groups of a population
Holoendemic: endemic in most of the children in a population, with the adults in the same population being less often affected
Epidemic: a disease occuring suddenly in numbers far exceeding those attributable to endemic disease; occuring suddenly in numbers clearly in access of normal expectancy
Pandemic: a widespread epidemic distributed or occuring widely throughout a region, country, continent, or globally
Epizootic: of, or related to a rapidly spreading and widely diffused disease affecting large numbers of animals in a given region
Establishing Reliability
The reliability of any measuring tool is the extent to which that tool measures in a consistent fashion. Reliability can be established through test-retest and interrater methods. Reliability is usually expressed in terms of correlation coefficients.
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Establishing Validity
Measuring instruments can be reliable (consistent) and yet lack validity (accuracy or truthfulness). Validity is the extent to which a measuring instrument measures what it is designed to measure. Predictive validity is an estimate of an instrument's ability to predict which participants will develop a particular condition and which ones will remain disease-free.
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