As a parent, you might struggle with your child's privacy. While cleaning his room, the temptation to look at a crumpled stack of papers on the desk, flip through an unlocked diary, or poke around the closet can be too strong to resist. And what do you do if you actually find something? Will you destroy your child's trust if you admit to an invasion of privacy? These are tough questions.
I believe it is important to respect a child's right to privacy but only up to a point. Your child's safety should always remain the primary issue and concern. Thus, you need to be educated about the signs of substance and physical abuse, depression, etc. These include marked changes in behavior or mood, uneven sleeping patterns, drastic changes in appetite, etc. As a responsible parent, you must be observant, but not spy on your child at the same time. Spend time alone with your child, this will provide opportunities for your child to share his feelings.
Remember, teens are scared to discuss certain issues with you. They will talk to you about these issues only if they trust you. The same goes for your child. He'll open up to you only if he's assured that you're not going to judge him harshly. Talk to him about your past; about your life as a teenager. It's always better to talk to your children, to have a conversation with them, rather than accusing them of things based on your assumptions and asking for explanations.
... only up to a certain threshold. Teens want special space, usually their bedroom, which will reflect their moods, interests, and search for a sense of identity. However, as a parent, you need to set some guidelines up front. Tell him that you will let him have his space, just the way he wants; however, if you suspect something to be seriously wrong, the same privacy will be at certain risk.
However, if there are strong signs that hint of trouble, then you have to be strict and firm. Communicate with him as though you're his friend, but if you think he's taking the liberty you give him for granted, be firm while talking to him. At all times, in all situations, and under all circumstances, he is expected to respect you and your rules. He shouldn't be intimidated by you; don't stop him from approaching you. At the same time, however, don't let him take you for granted.