My Son Is Suffering From Depression Combined With Insomnia. He

My son is suffering from depression combined with insomnia. He is presently hospitalized. His depression is being treated with Pristiq and after 2 weeks appears to be functionning. Unfortunate , his chronic insomnia persists and has been a problem for a few years. His chronic insomnia is being treated with Seraquil and Zopiclone. This combination is not functioning and he continues to wake up at 3am and fails to fall back asleep. My son wants to recommend Nozinan low dosage to his doctor. The attending phychiatrist is resisting this prescription raising the risk of tardive dyskinesia......please advise....thank you