Table 2.

Prevalence of Depression in Past Year Among Current Non-Daily, Daily, and Lifetime Never-Smokers (NSDUH, 2005–2013, US Persons Aged 12 Years and Older)

Smoking status	2005a	2006	2007	2008	2009	2010	2011	2012	2013	Linear trend
	Prevalence of past-year depression									Unadjusted OR (95%CI)	p b	Adjusted OR (95%CI)	p b
Total sample (n)	4700	4266	4438	4372	4509	4570	4662	4764	4867	1.01 (1.01, 1.02)	t = 2.83 (.0064)	1.01 (1.00, 1.03)	t = 2.20 (.0317)
%	6.62	6.47	6.86	6.82	6.87	6.94	6.88	7.16	7.16
SE	0.22	0.18	0.18	0.20	0.20	0.19	0.19	0.2	0.2
Current non-daily smokers (%)	9.06	9.25	8.97	9.18	10.31	9.55	9.68	10.13	10.10	1.02 (1.00, 1.03)	t = 2.17 (.0343)	1.03 (1.01, 1.04)	t = 3.27 (.0018)
SE	0.59	0.54	0.71	0.66	0.69	0.59	0.64	0.79	0.72
Current daily smokers (%)	10.44	10.58	12.04	10.72	11.10	11.05	12.13	10.96	10.78	1.01 (0.99, 1.02)	t = 0.62 (.5396)	1.01 (0.99, 1.03)	t = 0.79 (.4305)
SE	0.60	0.50	0.57	0.58	0.59	0.64	0.69	0.57	0.59
Lifetime never-smokers (%)	5.09	4.78	4.67	5.24	4.66	4.98	4.94	6.01	5.51	1.02 (1.01, 1.03)	t = 3.33 (.0015)	N/A	N/A
SE	0.31	0.25	0.22	0.28	0.22	0.21	0.2	0.24	0.28
c Differential time trend: year as continuous × smoking status										F(2) = 0.98(0.3822)		N/A
d Differential time trend: year as continuous × smoking (current non-daily vs. current daily smoker)										F(1) = 0.75(0.3898)		F(1) = 1.19(0.2800)
e Differential time trend: year as continuous × smoking (current non-daily vs. never-smoker)										F(1) = 0.18(0.6739)		N/A

CI = confidence interval; NSDUH = National Survey on Drug Use and Health; OR = odds ratio; SE = standard error; US = United States. Odds ratios are for past-year depression, versus no past-year depression. Logistic regressions were applied to examine the time trend within each particular group. An odds ratio greater than one indicated a significant trend for the prevalence of depression among each smoking category to increase during 2005–2013, and p-value for t tests showed the significance of time trends. Adjusted models: adjusted for age (12–17 years old, 18–25 years old, 26 years old or older) gender (male, female), total annual family income (<$20 000, $20 000–$74 999, ≥$75 000), nicotine dependence (yes, no), and cigarettes per day (1–5 cigarettes per day, 6–15 cigarettes per day, 16 or more cigarettes per day). Bold signifies p < .05.

^a2005 as reference year.

^b p-value for t test when beta = 0.

^cDifferential time trend among all smoking categories—slope over time differed by smoking status (non-daily, daily, and lifetime never-smokers), an interaction term between year and smoking was included in the regression.

^dDifferential time trend—slope over time differed by smoking status (non-daily vs. daily smokers), an interaction term between year and smoking was included in the regression.

^eDifferential time trend—slope over time differed by smoking status (non-daily vs. lifetime never-smokers), an interaction term between year and smoking was included in the regression.