Table 2.

Instrumental Variables Specification Tests

Tests	Combinations of instrumental variables
	Non KP pharmacy use		Happy + non KP pharmacy use		Calm + non KP pharmacy use		Happy + Calm		Happy + Calm + non KP pharmacy use
	Stats	P-value	Stats	P-value	Stats	P-value	Stats	P-value	Stats	P-value
Smith-Blundell test of exogeneity	6.553	0.011	22.907	<0.001	28.324	<0.001	26.976	<0.001	31.376	<0.001
Sargan Over Identification Test	--*	--	0.528	0.468	0.759	0.384	0.060	0.806	0.703	0.704
Basmann Over Identification Test	--*	--	0.525	0.469	0.755	0.385	0.060	0.807	0.699	0.705
Staiger-Stock Weak Instrument Test	24.710	<0.001	24.450	<0.001	26.400	<0.001	19.740	<0.001	19.480	<0.001

^*Over identification tests were not performed when only one instrument was used to avoid exact identification problem