Tincture of opium, and later morphine, were at one time quite commonly (and successfully) given to treat depressive and panic states in patients; however with certain caveats.
Here's a couple extracts from historical literature :
"Several hundred patients suffering from the depressed stage of manic depressive insanity were given large doses of opium orally in many instances for periods of from six months to one year. Not one of these patients ever knew what drug he was taking or ever showed any untoward results when it was withdrawn, or in any other way gave evidence of a desire to continue its use."
- Journal of the American Medical Association, 1920
"Opium is indispensable in dealing with the fear states of the melancholic individual. But here we make the surprising discovery that the continued administration of opium, in the form of opium tincture, during the melancholic mental disturbances, even when continued over a long period of time does not produce drug addiction. That is, it does not, provided that the dosage is adapted to the diseased mental state of the patient and provided that the doctor is careful to withdraw the drug at the correct time. " - Dr. Paul Wolff, Weekly Journal of German Medicine, 1931
" Opium is indispensable in many cases of endogenous depressions. The prescription of opiates for states of depression is unobjectionable also because we know from experience that the depressed persons feel no need for narcotics when the depression has passed away, and practically never become addicts. " - Dr. Karl Bonhoeffer, Weekly Journal of German Medicine, 1931
... in response to this particular discussion (published under the line 'When is the prescription of opiates medically justified?'), another physician, director of the Berlin Sanitarium where morphine was used for some psychiatric patients, pointed out :
"... but also ONLY in endogenous, that is in periodic melancholy arising from a constitutional basis. Warning must be issued against the administration of opiate preparations in cases of reactive depression - that is, depression in reaction to the vicissitudes of life. In these cases, it leads with especial ease to the development of addiction. "
... Makes perfect sense to me.