Table 4.

Model selection and optimal mixed model analysis of course of depression severity over the first year of follow-up

Selection of optimal mixed model
	Unadjusted			Adjusteda
Consecutive steps and tested effect	χ2	df	p	χ2	df	p
1 – Linear effect of time	51.5	1	<0.001	51.2	1	<0.001
2 – Quadratic effect of time	18.2	1	<0.001	16.2	1	<0.001
3 – Main effect of class	24.9	3	<0.001	14.8	3	0.002
4A – Interaction of class with linear time	14.0	3	0.003	14.8	3	0.002
4B – Interaction of class with quadratic time	10.8	3	0.013	12.6	3	0.006
Best fitting model for course of depressive symptoms
	Unadjusted			Adjusteda
Effects	B (s.e.)	F/t	p	B (s.e.)	F/t	p
Time (years since baseline)	−7.3 (3.1)	22.0	<0.001	−6.9 (3.0)	20.3	<0.001
Time2	8.2 (1.9)	18.4	<0.001	7.8 (1.9)	16.2	<0.001
Class
Class C ‘Severe inflammation’ (n = 27)	Referenceb	–	–	Referencec	–	–
Class A ‘Healthy’ (n = 181)	−1.7 (2.5)	0.7	0.513	−0.7 (2.4)	0.3	0.770
Class B ‘Inflammatory-metabolic dysregulation’ (n = 137)	2.8 (2.6)	1.1	0.287	1.6 (2.4)	0.7	0.512
Class D ‘Mild inflammation’ (n = 14)	0.2 (4.1)	0.1	0.957	−0.8 (3.9)	0.2	0.847
Class × Time:
Class C × Time	Referencec	–	–	Referencec	–	–
Class A × Time	−6.3 (2.6)	2.6	0.017	−6.5 (2.5)	2.5	0.010
Class B × Time	−5.6 (2.7)	2.7	0.041	−5.1 (2.6)	0.2.0	0.052
Class D × Time	−0.6 (4.7)	4.7	0.902	−0.8 (4.5)	0.2	0.862

^aAdjusted for age, sex, years of education, smoking, alcohol use, physical activity, somatic comorbidity, global cognitive functioning and use of antidepressants.

^bDifference between class A and class B in unadjusted analysis (t = 3.163; p = 0.002), not in adjusted analysis (t = 1.590; p = 0.113).

^cNo other significant differences between classes (p < 0.05) were found.