According to this review by researchers from Moi University (Kenya), Indiana University (USA), Regenstrief Institute (USA) and University of Toronto (Canada), the most commonly used drug among street children in low- and middle-income countries is inhalants, things like glue, acetone, gasoline, and paint thinner. Street children likely gravitate toward inhalants because they're cheap and legal, and therefore easy to get. (In contrast, street children in high-income countries tend to favour injection drugs, such as heroin.)

Use of volatile solvents such as glue and gasoline is a major obstacle to street children being re-integrated into society and having a healthy and productive life once they are off the streets. Inhalants have been linked to cognitive and neurological impairment and psychological and physical dependence. They are also linked to sudden death from cardiac arrhythmia and other causes.

The prevalence of drug use among street children varies widely among countries, from 14% in Nigeria to 92% in Honduras and Brazil. These estimates are several times higher than the World Health Organization's estimates of drug use among non-street youth globally. The most common reasons street children give for using drugs are peer pressure, escapism, pleasure, curiosity, and increasing courage and strength for life on the streets.

Dr. Paula Braitstein, the senior author of this study, says that one of the most valuable outcomes of this review is an understanding of what new research needs to be done. "As a result of this review, we learned that we don't really know what causes street children to start and stop using drugs. We also found that many studies of street children focus on boys, so we have even less information about girls' drug use. Finally, although we know that some street children exchange sex for drugs or have sex while under the influence of drugs, little else is known about the link between drug use and risky sex behavior. There are several critical gaps in our knowledge that we need to fill."