Table 3.

Association of patients' actual prescription with physicians' previous prescription for TCAs vs. SSRIs and paroxetine vs. SSRIs, adjusted for year of first prescription

Instrument	TCAs vs. SSRIs	Paroxetine vs. SSRIs
	Risk difference (95% CI)	Risk difference (95% confidence interval)
Prior prescription	14.90 (14.42, 15.38)	27.72 (26.69, 28.76)
N	886,735	390,600
Number of physicians (clusters)	6,555	5,144
F-test	F(1, 6554) = 3,663	F(1, 5143) = 2,770
Partial r2	0.02	0.08

Abbreviations: TCA, tricyclic antidepressant; SSRI, selective serotonin reuptake inhibitor; CI, confidence interval.

All CIs robust for heteroskedasticity and clustered by physician. Risk difference is difference in probability of TCA or paroxetine actually being prescribed if the physician previously prescribed a TCA or paroxetine (e.g., in row 1, if the physician previously prescribed a TCA, their current patient is 15% more likely to also be prescribed a TCA than a SSRI).