Mean days used of the most common problem drug at baseline were 14.40 ( SD , 11.29 ) ( brief intervention ) and 13.25 ( SD , 10.69 ) ( enhanced care as usual ) ; at 3 months postintervention , means were 11.87 ( SD , 12.13 ) ( brief intervention ) and 9.84 ( SD , 10.64 ) ( enhanced care as usual ) and not significantly different ( difference in differences , = 0.89 [ 95 % CI , -0.49 to 2.26 ] ) .