1. Communicate Openly
Most teens go through periods of depression during adolescence, but you can keep it from spiraling into something more serious by establishing an open and honest connection with your teen. Let him know that he can come and talk to you about anything if he needs to, and that you won't judge him or try to manage him if he has a problem. Be ready to listen as much as talk, and to express your support for him regardless of the circumstances. That doesn't mean you shouldn't discipline him if the situation warrants it, but it does mean using compassion and respect at all times. The earlier you can establish good patterns of communication, the less likely your teen's depression will become worse.
2. Be Aware of Events in Your Teen's Life
Depression can reverberate through all aspects of a teenager's life. School performance may suffer, she may undergo radical changes in mood or dress style, interest in previously enjoyable activities may drop, and there may be an unusually high amount of defiance--even criminal behavior such as shoplifting. While you shouldn't smother her or follow her everywhere she goes--teens require a certain amount of independence--it helps to be aware of the activities she's involved in and take an interest in what's happening in her life. If you can spot early warning signs, you may be able to prevent a slip into serious depression. Also keep in mind that girls are much more likely to suffer from teen depression than boys. Body issues and self-esteem tend to play a larger role in their psyche, which you can help temper if you are aware of it early.
3. Encourage Positive Activities
It can be tough for parents to steer a teen toward a particular outlook or activity. Anything a parent does is, by definition, monumentally uncool. But at the same time, it helps to nourish positive goals in your teen and encourage him to pursue activities that he finds fulfilling. Regular exercise can keep energy levels high, while creative endeavors--even if it's just writing in a diary or blog--encourage expressiveness instead of just bottling up emotions. A healthy diet and avoidance of drugs and alcohol can further cement an optimistic mindset. The earlier those habits are encouraged, the more effectively they can prevent depression.
4. Look Into Therapy
Therapy is a common treatment for depression, but it can be used as a preventative measure in some cases, especially if there is a history of depression in your family. Cognitive behavioral therapy helps identify the causes of negative thought patterns and works to replace them with a more positive outlook. It can also help her cope with negative emotions when they occur instead of just bottling them up or reacting to them inappropriately. Even if it doesn't prevent the onset of depression, it can give an at-risk teen better coping skills, allowing her to address it from a position of greater strength.
