Veterans with PTSD were 2 1/2 times more likely to be on these narcotics. The researchers also were also concerned about the quantity of drugs prescribed.

"These patients tend to receive higher dose opiates than their counterparts and would request early refills of their opiates, which indicates that they are using them more quickly than they should be," Seal said.

Many of the veterans on these drugs -- whether they were mentally ill or not -- had higher rates of accidents, alcoholism, violent injuries, suicides and overdoses. Seal says the findings demonstrate that alternative methods of treatment, such as physical therapy, talk therapy or acupuncture, should be offered more widely.

"The study really woke us up to the reality of the serious adverse consequences that can occur with the use of opiates in returning Iraq and Afghanistan veterans who have pain and mental health problems," Seal said.

Yochelson says treating post-traumatic stress disorder will take more than a quick fix.

"Frankly, if they've been on multiple deployments and perhaps been there for 12 or 18 months or longer, or even over a period of several years, several deployments and never had it addressed until now, I think that treatment period may be going on for several years and maybe indefinitely," Yochelson said.