Table 1.

Item Response Theory model parameters from MADRS and YMRS Graded Response Models.

			Discrimination	Difficulty
Item		α	BM	β 1	β 2	β 3	β 4	β 5	β 6	β 7	β 8
Apparent Sadness	MADRS 1	2.64	3.00	−1.27	0.38	2.41	3.41	5.66	7.39
Reported Sadness	MADRS 2	3.23	2.52	−1.80	−0.66	1.34	2.87	5.65	7.74
Inner Tension	MADRS 3	1.31	1.78	−1.28	−0.75	0.71	2.04	4.24	5.73
Reduced Sleep	MADRS 4	0.68	1.45	−0.05	0.18	0.77	1.26	2.67	3.86
Reduced Appetite	MADRS 5	0.91	2.64	0.82	1.02	1.85	2.85	4.04	5.23
Concentration Difficulties	MADRS 6	1.57	1.45	−1.32	−0.87	0.33	1.34	3.86	5.22
Lassitude	MADRS 7	2.14	2.08	−1.24	−0.38	1.05	1.74	4.45	6.87
Inability to Feel	MADRS 8	2.60	2.70	−0.49	0.25	1.67	2.67	5.27	6.81
Pessimistic Thoughts	MADRS 9	2.24	2.55	−1.37	−0.51	1.12	2.48	5.46	8.10
Suicidal Thoughts	MADRS 10	1.87	3.64	0.69	1.48	2.70	3.58	5.50	7.89
Elevated Mood	YMRS 1	2.47	4.45	1.23	2.88	5.46	8.21
Increased Motor Activity-Energy	YMRS 2	2.83	4.19	1.44	3.25	4.32	7.75
Sexual Interest	YMRS 3	1.26	4.75	2.22	2.95	4.83	9.00
Sleep	YMRS 4	0.99	3.10	0.65	1.23	3.20	7.32
Irritability	YMRS 5	1.38	4.04	−0.89	−0.18	1.48	2.87	4.58	5.72	8.01	10.69
Speech	YMRS 6	2.18	4.36	1.18	1.72	2.71	3.22	4.68	5.30	7.54	8.51
Language-thought Disorder	YMRS 7	1.89	4.25	0.46	2.00	5.25	9.28
Content	YMRS 8	1.88	4.67	1.39	2.43	3.79	4.61	5.35	5.73	6.84	7.18
Disruptive-Aggressive Behavior	YMRS 9	2.15	7.04	1.49	2.90	4.99	6.55	8.33	9.25	10.95	11.88
Appearance	YMRS 10	0.37	4.68	1.43	3.11	5.88	8.28
Insight	YMRS 11	0.54	4.05	2.78	4.09	4.58	4.74

Note. Discrimination (α) refers to an item's ability to discriminate between different latent levels of manic (YMRS) or depressive (MADRS) symptom severity (i.e., theta, θ). Difficulty parameters (β) reflect the standardized latent level of symptom severity at which subsequent response options become more probable than the previous option.