The reasons that opiate efficacy is not often discussed is unknown to this author. Logic would suggest that the FDA must have determined that emotional pain is less severe than physical pain, but the fact that 90% of suicides are caused by mental illness--most commonly depression--rather thoroughly refutes this particular misconception. (http://www.suicide.org/suicide-causes.html)
Furthermore, the drugs currently used to treat depression are addictive, the only difference being that the person coming off antidepressants generally is glad to be doing so because of the many side effects. There's also no "high" that they might miss. That difference is probably not as true as it might at first seem, however, because people dependant upon medically prescribed opiates have mostly left that part of the experience behind them as they became tolerant to the drug. In fact studies show that less than 5% of people prescribed opiates become dependent, and it's important to understand that dependency is NOT the same as addiction! (http://www.rsdhope.org/drug-therapies-for-crps.html)
When searching the internet for information on the subject, one gets the feeling that much of what is known on the subject has been supressed. With persistence the data can be found, though, and one of the best I've seen can be found in documentation on development of a new drug, ALKS-5461 (https://en.wikipedia.org/wiki/ALKS-5461). The FDA has reportedly placed this drug on the fast track for approval. It contains a strong narcotic in combination with another drug that supresses any euphoria the patient might otherwise experience from taking it. I don't personally like the idea of taking a drug with it's own set of side effects, that I don't need, for the purpose of making it difficult to abuse. If approved it will also undoubtably be very expensive, but it may be a step in the right direction.
Incidence of depression is increasing at an alarming rate in the U.S., so don't dismiss the possibility that you or a loved one may at some point become a victim. (http://www.nimh.nih.gov/health/statistics/prevalence/major-depression-among-adults.shtml)