PHQDEP 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)

• trouble falling or staying asleep, or sleeping too much? (PHQSLEEP)

• 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.

In 2023, NHIS combined PHQDEP and PHQINTR into a two-item scale (PHQSCREEN) meant as a screener for further evaluation, not as a diagnostic.