Investigating the effect of zinc supplementation on probability of relapse and mental health in patients with opioid use disorder undergoing methadone maintenance treatment

Table 3 A comparison of DASS-21 scores in study groups

Variables	Groups	Before intervention Mean ± SD	One month after intervention Mean ± SD	Three months after intervention Mean ± SD	P¹	P³	Partial eta square^a
Variables	Groups	Before intervention Mean ± SD	One month after intervention Mean ± SD	Three months after intervention Mean ± SD	P²	P³	Partial eta square^a
Depression	Control	27.05 ± 7.97	27.29 ± 5.09	27.58 ± 5.34	0.89	0.87	0.013
Depression	Intervention	29.47 ± 6.75	26.82 ± 6.15	26.29 ± 7.00	0.01	0.87	0.013
Anxiety	Control	24.17 ± 7.09	25.58 ± 5.41	26.00 ± 6.51	0.139	0.39	0.021
Anxiety	Intervention	26.64 ± 7.43	24.00 ± 6.47	21.38 ± 6.14	< 0.001	0.39	0.021
Stress	Control	22.23 ± 7.13	25.29 ± 5.56	28.17 ± 6.57	< 0.001	0.08	0.044
Stress	Intervention	24.67 ± 6.43	22.58 ± 6.77	20.64 ± 8.49	0.001	0.08	0.044
Total score	Control	73.47 ± 12.25	78.17 ± 10.02	81.76 ± 13.08	0.001	< .001	0.390
Total score	Intervention	80.79 ± 12.32	73.41 ± 13.61	68.32 ± 15.91	0.001	< .001	0.390

P¹ = Significant for the trend mean values in the control group (Repeated measures ANOVA)
P² = Significant for the trend mean values in the intervention group (Repeated measures ANOVA)
P³ = Significant for the total difference in means (before and after the intervention) between the intervention and control groups (Repeated measures ANOVA)
^aPartial Eta Square interpret: 0.01 ∼ small, 0.06 ∼ medium, > 0.14 ∼ large

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