% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/data.R
\docType{data}
\name{phq9}
\alias{phq9}
\title{PHQ-9 Depression Screener (NHANES Subsample)}
\format{
A data frame with 600 rows and 12 variables:
\describe{
\item{q1}{Little interest or pleasure in doing things. Integer 0--3.}
\item{q2}{Feeling down, depressed, or hopeless. Integer 0--3.}
\item{q3}{Trouble falling/staying asleep, or sleeping too much.
Integer 0--3.}
\item{q4}{Feeling tired or having little energy. Integer 0--3.}
\item{q5}{Poor appetite or overeating. Integer 0--3.}
\item{q6}{Feeling bad about yourself --- or that you are a failure
or have let yourself or your family down. Integer 0--3.}
\item{q7}{Trouble concentrating on things, such as reading the
newspaper or watching television. Integer 0--3.}
\item{q8}{Moving or speaking so slowly that other people could have
noticed --- or the opposite, being so fidgety or restless that
you have been moving around a lot more than usual. Integer 0--3.}
\item{q9}{Thoughts that you would be better off dead, or of hurting
yourself in some way. Integer 0--3.}
\item{gender}{Self-reported gender, factor with levels
\code{"Female"} and \code{"Male"} (31 respondents with missing values).}
\item{age}{Age in years (integer, range 15--85).}
\item{edu}{Highest educational attainment, factor with levels
\code{"Elementary School"}, \code{"High school"}, \code{"University"}.}
}

Each PHQ-9 item uses a four-point ordinal response scale, scored
0 (\code{"Not at all"}), 1 (\code{"Several days"}), 2 (\code{"More than half the days"}) and 3 (\code{"Nearly every day"}).
}
\source{
U.S. Centers for Disease Control and Prevention, National Center for
Health Statistics. \emph{National Health and Nutrition Examination Survey},
September 2024 release.
\url{https://wwwn.cdc.gov/nchs/nhanes/search/datapage.aspx?Component=Questionnaire&CycleBeginYear=2024}.
NHANES data are released to the public domain by the U.S. federal
government (\url{https://www.cdc.gov/nchs/policy/data-release-policy.html}).
}
\usage{
phq9
}
\description{
A processed subsample of the Patient Health Questionnaire 9-item (PHQ-9)
depression screener from the U.S. National Health and Nutrition
Examination Survey (NHANES), September 2024 release. Six hundred
respondents were drawn at random from the cycle's PHQ-9 module subject
to having complete responses on all nine items, while retaining a
realistic share of respondents with a sum-score of zero (n = 8) so
that floor behaviour can be illustrated in a Rasch analysis.
}
\details{
The dataset is a \emph{processed subsample} intended for teaching and for
the package's worked example; it should not be treated as a canonical
NHANES microdata file. Users wishing to validate against NCHS-published
figures should download the original public-use microdata directly
from the NHANES website (see \emph{Source}).
}
\examples{
data(phq9)
str(phq9)
summary(rowSums(phq9[, 1:9]))
}
\references{
Kroenke, K., Spitzer, R. L., & Williams, J. B. W. (2001). The PHQ-9:
Validity of a brief depression severity measure. \emph{Journal of General
Internal Medicine}, 16(9), 606--613.
\doi{10.1046/j.1525-1497.2001.016009606.x}
}
\keyword{datasets}
