Table 2.

PHQ-9 items and discrimination parameters from the generalized partial credit model

Item Number	Description	Discrimination Parameter
1	Little interest or pleasure in doing things	1.95
2	Feeling down, depressed, or hopeless	2.40
3	Trouble falling or staying asleep, or sleeping too much	0.93
4	Feeling tired or having little energy	1.37
5	Poor appetite or overeating	1.08
6	Feeling bad about yourself - or that you are a failure or have let yourself or your family down	1.90
7	Trouble concentrating on things, such as reading newspaper or watching television	1.41
8	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	1.29
9	Thoughts that you would be better off dead or of hurting yourself in some way	1.77