Table 1.

Item‐total correlations and Cronbach's alpha values for K6 and K10

Questions	Item‐total correlation (K6)	Item‐total correlation (K10)	Cronbach's alpha if item deleted	Item–item correlations
				Q1	Q2	Q3	Q4	Q5	Q6	Q7	Q8	Q9	Q10
Q1 (tired out for no good reason)	‐	0.59	0.92	1	0.50	0.47	0.45	0.49	0.43	0.50	0.46	0.43	0.42
Q2 (nervous)	0.61	0.66	0.91	‐	1	0.63	0.48	0.56	0.50	0.56	0.53	0.39	0.44
Q3 (so nervous that nothing could calm you down)	‐	0.72	0.91	‐	‐	1	0.53	0.60	0.63	0.54	0.63	0.45	0.49
Q4 (disappointed or hopeless)	0.72	0.72	0.91	‐	‐	‐	1	0.60	0.52	0.64	0.60	0.48	0.61
Q5 (restless or fidgety)	0.70	0.75	0.91	‐	‐	‐	‐	1	0.69	0.63	0.61	0.46	0.48
Q6 (so restless that you could not sit still)	‐	0.71	0.91	‐	‐	‐	‐	‐	1	0.56	0.63	0.45	0.47
Q7 (depressed)	‐	0.77	0.91	‐	‐	‐	‐	‐	‐	1	0.76	0.55	0.54
Q8 (so depressed that nothing could cheer you up)	0.73	0.78	0.91	‐	‐	‐	‐	‐	‐	‐	1	0.52	0.55
Q9 (everything was an effort)	0.60	0.61	0.92	‐	‐	‐	‐	‐	‐	‐	‐	1	0.50
Q10 (worthless)	0.66	0.65	0.91	‐	‐	‐	‐	‐	‐	‐	‐	‐	1