coding symptoms

The guidelines say that you don't code systems that are integral to the disease process separate. I work in mental health and there are a lot of things that can either be symptoms or separate conditions themselves. For example nearly every mental health issue can have insomnia as a symptom, so I only code it separately if the doctor specifies that is is a separate condition. The same goes for anxiety. It is a very common symptom of things such as bipolar disorder and even major depressive disorder, so I only code it separately if the doctor specifies it as a separate diagnosis. This is was I was taught to do by the person that trained me. Now I have a new coder here freshly out of school who argues with me on these types of things, saying that the doctor has to relate them or you code them separately. Which should it be?