I've followed Dr. Barry Krakow's work for years, starting when I was a fellow at Dartmouth. Dr. Krakow is an expert on insomnia, nightmare treatments, and obstructive sleep apnea (OSA). I have a copy of one of his insomnia books, called Sound Sleep, Sound Mind, and I recommend it highly. Besides treating nightmares, Dr. Krakow has brought to the mainstream the common co-existence of insomnia and OSA, and the relationship to each other. Now, he has published an exciting paper in the Mayo Clinic Proceedings, but I don't have access to it - all I have is the abstract.
In this study, Dr. Krakow evaluated over 1200 patients with chronic insomnia. Almost three-fourths of the insomnia patients did not respond to medications for their insomnia. Dr. Krakow studied 942 of them in the sleep lab using the most modern testing equipment, not done in older insomnia studies. Results showed that over 90% of these patients had moderate to severe OSA! The results are somewhat surprising with respect to the percentage of insomnia patients that had undiagnosed OSA. In my clinic, I regularly get patients referred to me for "insomnia" that actually have OSA, and sometimes it is severe. In these cases, treating the OSA usually improves sleep quality significantly such that sleeping pills are no longer needed.
The bottom line is that patients with chronic insomnia that do not respond to medications may benefit from referral to a sleep specialist for evaluation of underlying medical causes of the insomnia, such as OSA.