Is Tea helpful in stress??

We have become addicted to tea in our routine life, in offices, at home, in bazars etc. After having a cup we feel mentally relaxed and comfortable. Is it due to tea or feeling of having tea that makes us relaxe.??My collegue, named, Saima,often looks me gripping a cup of tea in her office door or walking to and fro near her office sipping contineously hot tea. I asked her about her habbit of taking tea but she had no plausible answer. Do you have??