PHQSLEEP is part of the Patient Health Questionnaire depression scale (PHQ) that, according to the 2019 Survey Description, "is used in clinical settings and in population-based studies to screen for symptoms indicative of a possible clinically significant depression and assess severity of depressive disorders." Additional PHQ questions that are included as part of the NHIS are:

Over the last two weeks, how often have you been bothered by...

• little interest or pleasure in doing things? (PHQINTR)

• feeling down, depressed, or hopeless? (PHQDEP)

• feeling tired or having little energy? (PHQENGY)

• poor appetite or overeating? (PHQEAT)

• feeling bad about yourself, or that you are a failure, or have let yourself or your family down? (PHQBAD)

• trouble concentrating on things, such as reading the newspaper or watching television? (PHQCONC)

• 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? (PHQMOVE)

The NHIS offers a categorical summary measure, PHQCAT, that is based on the summed responses to the above PHQ variables. Users can also sum these variables themselves to create a total score that can be used for analysis and assessing severity of symptoms. For more information on how to calculate the total score for the PHQ, please see PHQCAT.