Never heard the thing about melatonin being unsafe long-term. Only good things like it lowering cancer risk and when we age, we produce less of it.

Our doctors "prescribes" it to many of his patients for long-term use (like the rest of their lives).

Valerian root is part of a supplement that greatly helps sleep for several people I know who USED TO BE diagnosed with bipolar, called Nutrasleep. Here is some information: Sleep: Timing of Melatonin, Light, Dark, & Use of Other Aids and you can get more information on sleep topics at Talk About Sleep

I wonder if you have an underlying treatable medical condition such as a hormonal issue, sleep disorder, food sensitivity, etc. So many things can get diagnosed as "mental" simply because they cause psychiatric symptoms. (See here and here)