The clinical effectiveness of group art therapy did not significantly differ between participants with more or less severe negative symptoms [ interaction for difference in PANSS = 1.7 , 95 % CI ( -8.6 to 12.1 ) , P = 0.741 ] , or between those who did and did not express a preference for art therapy [ interaction = 3.9 , 95 % CI ( -6.7 to 14.5 ) , P = 0.473 ] .