Table 2.

Causal effect of tooth loss on a total score of PHQ-8 (ranges 0–24); N = 169 061

	Coef.	95% CI	p-Value	F-statistic
Treatment variable: number of lost teeth
OLS estimation
The number of lost teeth (continuous)	0.134	0.131–0.136	<0.001	–
2SLS estimation
Second stage
The number of lost teeth (continuous)	0.146	0.008–0.284	0.039	–
First stage
Drinking water fluoridea	−0.564	−0.693 to −0.435	<0.001	73.4
Reduced form
Drinking water fluoridea	−0.082	−0.162 to −0.002	0.044	–
Treatment variable: having lost ⩾1 tooth
OLS estimation
Having lost ⩾1 tooth (ref. full dentition)	1.643	1.600 to 1.687	<0.001	–
2SLS estimation
Second stage
Having lost ⩾1 tooth (ref. full dentition)	3.141	0.100 to 6.182	0.043	–
First stage
Drinking water fluoridea	−0.026	−0.035 to −0.018	<0.001	36.1
Reduced form
Drinking water fluoridea	−0.082	−0.162 to −0.002	0.044	–
Treatment variable: having lost all tooth
OLS estimation
Having lost all teeth (ref. having ⩾1 tooth)	2.334	2.238 to 2.430	<0.001	–
2SLS estimation
Second stage
Having lost all teeth (ref. having ⩾1 tooth)	7.251	0.053 to 14.449	0.048	–
First stage
Drinking water fluoridea	−0.011	−0.015 to −0.007	<0.001	31.7
Reduced form
Drinking water fluoridea	−0.082	−0.162 to −0.002	0.044	–

CI, confidence interval; OLS, Ordinary Least Squares; PHQ-8, the eight-item Patient Health Questionnaire depression scale; 2SLS, two-stage least-squares.

Adjusted for year of birth, wave of survey, gender and state of residence.

^aSum of the proportion of people supplied with fluoridated water in the county of residence during the age of 5–14 years (rescaled between 0 and 1).