“…Studies on the course of schizophrenia have found that substance abusers not only have an higher frequency of relapse (Linszen et al, 1994;Rosenbaum et al, 2005), higher health care cost (Bartels et al, 1993) and a worse social adaptation (Caton et al, 2007), but also present several clinical conditions such as more severe hostile attitudes , more frequent thought disorders (Soyka et al, 2001) and fewer severe negative symptoms (Hambrecht and Häfner, 1996;Bühler et al, 2002;Compton et al, 2004;Bersani et al, 2002).…”