OBJECTIVE To examine the effect of attending a medical school with an active policy on restricting gifts from representatives of pharmaceutical and device industries on subsequent prescribing behavior. METHODS Difference-in-differences approach. METHODS 14 US medical schools with an active gift restriction policy in place by 2004. METHODS Prescribing patterns in 2008 and 2009 of physicians attending one of the schools compared with physicians graduating from the same schools before the implementation of the policy, as well as a set of contemporary matched controls. METHODS Probability that a physician would prescribe a newly marketed medication over existing alternatives of three psychotropic classes: lisdexamfetamine among stimulants, paliperidone among antipsychotics, and desvenlafaxine among antidepressants. None of these medications represented radical breakthroughs in their respective classes. RESULTS For two of the three medications examined, attending a medical school with an active gift restriction policy was associated with reduced prescribing of the newly marketed drug. Physicians who attended a medical school with an active conflict of interest policy were less likely to prescribe lisdexamfetamine over older stimulants (adjusted odds ratio 0.44, 95% confidence interval 0.22 to 0.88; P=0.02) and paliperidone over older antipsychotics (0.25, 0.07 to 0.85; P=0.03). A significant effect was not observed for desvenlafaxine (1.54, 0.79 to 3.03; P=0.20). Among cohorts of students who had a longer exposure to the policy or were exposed to more stringent policies, prescribing rates were further reduced. CONCLUSIONS Exposure to a gift restriction policy during medical school was associated with reduced prescribing of two out of three newly introduced psychotropic medications.