I have seen a lot of media hype around a recent study that found a relationship between receiving a lot of texts to using drugs, having sex, and other risky behaviours.
I must point out, due to the media's habit to "sell" stories instead of reporting them, that this is a correlation, not a cause! Correlation meaning that when texting is scored high, so is something like drinking. When texting decreases so does drinking. A causation means that texting causes drinking, or drinking causes texting. This study did not show causation.
What I feel is more likely the case is that there is an outlying factor, parenting. I feel that a lack of parental supervision is more likely to be the "cause" of the relationship between texting and risky behaviours. If parents supervised their kids cell-phone usage, such as no texting at night or during meals, they may have other rules that would help curb risky behaviours.
So please, don't think that because your child texts, that they are having sex or doing drugs. Just make sure you are implementing rules about texting in your home.
As I was writing this, someone I admire as a MFT wrote a much more sophisticated post about this study. I recommend you read what Ben Caldwell has to say about the study for a more in-depth look at correlations, and causations.