During childhood, young people typically remember the stages of their lives in time stamps of school years and summer vacations. There is always that one year when summer break ends and the boys come back with deeper "frogs" in their voices and extra height and the girls come back looking more like women. The onset of the teenage years not only tweaks fears and nerves within parents, but also in teens themselves.
Anxiety can be rampant during these awkward and jostling periods. There is an increase in awareness of social norms and fitting in, or not fitting in. This is also a time where identity development reaches a peak, as teenagers are trying on different versions of themselves based on their own internal values as well as those external to them. Cyber-bullying can also come into play, as teenagers are often using social media and adults are much less able to monitor these interactions. Finally, worry about the future starts to occur for many in high school with thoughts like: what college should I attend?... what will I major in?... what am I going to do with the rest of my life!?
A key parenting strategy is to prepare our growing kids for the situations they are likely to be in related to sexual intimacy, alcohol and drugs, and situations that may not be safe -- or where they can find themselves in trouble. Help them develop the critical thinking skills to evaluate a situation knowing that they all cannot be avoided. Be real and authentic. Give them a "get out of jail free card" where they can call you at any time for any reason when they do not feel safe - even if they are not supposed to be in the situation or place.
I also suggest giving your teenagers tools and tips on how to deal with their normal anxieties. Tell them to be aware of the present versus the future, because all anxious thinking occurs about the future. Tell them that if they focus on the present, they will worry less and be engaged in their current moment or day. Teach them the difference between worrying and thinking as worrying is not productive yet thinking allows us to plan. Ask them what they are thinking when feeling worried or scared. They will often find they are thinking about something that can go wrong or something bad that "could" happen. Let them know they can change their thinking so it is more reasonable and less catastrophic. Finally, encourage them to remember they are young and have a lot of life to live. I have found that things usually do work out if we let them.
For teenagers who are particularly aloof (or seem to be) or non-communicative, sometimes it's easier to offer them a book in a casual manner that they can pick up and read on their own time. Sometimes, kids just need to hear about others experiences so they cannot feel so alone and have the courage to talk to others. Finally, maybe a parent isn't the best person and your child would feel more comfortable taking to an aunt, cousin, grandparent, or counselor. It takes a village to raise kids. We parents can't do it all.
The key thing though is to let your teenagers know that you have empathy for their experience, that you've been there yourself, and that the anxieties and issues that arise are often a normal part of growing and being human.