While most of us who work in prevention target youth with our programming, we may not think about the complex processes that place children and adolescents at risk to substance use and
other problem behaviors. Prevention science gives us some important guidance in understanding these vulnerabilities and support for our ongoing work to prevent the initiation of substance use in youth.
Studies conducted in 15 different countries show that between 50 to 80% of first use of alcohol, tobacco, cannabis and cocaine occurs before the age of 20, while the brain is still developing.  Furthermore, research has shown that early onset of substance use is associated with more rapid progression to substance abuse. This research underscores the importance of preventing the initiation of substance use particularly among those most vulnerable. What determines vulnerability?
Each developmental stage from infancy through adulthood is associated with the growth of intellectual ability; language skills; cognitive, emotional, and psychological functioning, and the continued acquisition of social competency skills. Research has shown that any disruption of normal development makes an individual vulnerable to influences to engage in negative behaviors such as substance use. These problem behaviors can lead to other consequences such as, falling behind academically, difficulties in social relationships, etc. Therefore, prevention interventions need to be designed and implemented to address each developmental phase—i.e., infancy and early childhood, middle childhood, adolescence, and young adulthood--to prevent the onset of substance use and other potential behavioral problems.
As prevention professionals, we need to target children and adolescents before initiation happens by addressing the conditions that occur in the environments around these children that makes them vulnerable and influence their decision to use psychoactive substances and engage in other risky behaviors.
 Degenhardt L, Chiu W-T, Sampson N, Kessler RC, Anthony JC, et al. (2008) Toward a global view of alcohol, tobacco, cannabis, and cocaine use: Findings from the WHOWorld Mental Health Surveys. PLoS Med 5(7): e141. .http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2443200/pdf/pmed.0050141.pdf