There's no safe level of alcohol use for children under 18 years. Their brains and bodies are still developing and can be easily damaged. Using other drugs like cannabis, crystal meth, ecstasy and cocaine is never safe at any age. Using alcohol and other drugs isn't always the same thing as having a problem with them. But if your child is regularly using or overusing alcohol or other drugs, or feels that she can't have a good time without them, it's a very serious issue.