PDwS in the intervention group experienced greater improvement in knowledge scores ( 4.9 vs -0.5 ; p < 0.001 ) at post-treatment and ( 6.5 vs -0.7 ; p < 0.001 ) at three month-follow-up , greater reduction in symptom severity ( -26.1 vs 2.5 ; p < 0.001 : -36.2 vs -4.9 ; p < 0.001 , at follow-up times respectively .