World Health Organization (2004) documented that substance use or abuse and mental disorders are important causes of disease burden accounting for 8.8% and 16.6% of the total burden of disease in low income and lower middle-income countries, respectively. Alcohol use/abuse disorders alone contribute to 0.6%-2.6% of the total burden of disease in these countries. This cross-sectional descriptive study recruited 184 psychiatric patients seen at Bugando Medical centre and assessed them for substance involvement using the WHO Alcohol, Smoking and Substance Involvement Screening Test. The most frequently used substances among respondents were alcohol (59.3%), tobacco (38.6%), and cannabis (29.3%), while heroin and cocaine were least used (2.1% and 1.6%, respectively). Statistical significant difference existed between substance use and participants: level of education, formal employment, marital status, gender, family history of mental illness, and family history of substance use. About a third attributed their involvement into substance exclusively to peer pressure, 8.7 to both peer pressure and curiosity while 7.1% exclusively to curiosity. This result represents one of the most important risks to mental health, and is a leading factor that causes high rates of admission or reason to be seen by a psychiatrist, this cannot be ignored when managing psychiatric disorders and therefore calls for routing screening for substance involvement among clients seeking psychiatric treatment. It also calls for appropriate standard operation policy procedures that can be operationlized as a matter of clinical practice by mental health workers in their routine medical practice.
