et al., 2001; Mueser et al., 1990; Siris et al., 1988) in people with schizophrenia. The use of more than two drugs at the same time is also common (Soyka et al., 1993). Other drugs of abuse in this population include heroin, and hallucinogens; however, these are less often the drugs of choice (Margolese et al., 2004). A United Kingdom study reported that rates of co-occurring schizophrenia and substance abuse are increasing by about 10% per year, and afflicted co-morbid individuals’ average age decreasing from 38 years to 34 years during 1993 to 1998 (Frisher et al., 2004).
