Letter: Letter

From Mark Gillman and Frederick Lichtigfeld, South African Brain Research Institute

It has been suggested by other investigators and ourselves in various
scientific publications that the endogenous opioid system (EOS) is involved in
the placebo responses seen in pain, addictive withdrawal states and the
treatment of depression.

The findings covered by New Scientist seem to indicate that 75 per
cent of the benefit obtained in the treatment of depression by antidepressants
is related to their nonspecific placebo effects. A possible explanation for this
surprising finding is that expectation and other positive reinforcements that
the patient experiences during treatment could well activate the EOS, producing
the desired mood elevation.

If this is indeed the case, it would seem that other drugs which activate the
EOS may also have antidepressant actions. Indeed, morphine, which is the
prototype opioid, has well-known antidepressant actions which were used in the
19th century. Analgesic nitrous oxide (N₂O), the first gaseous opioid,
has already been shown to have antidepressant properties in clinical practice.
And, since its introduction over a century ago, N₂O has been shown to
cause no clinically significant addiction in the millions of cases in which it
has been used at both analgesic and anaesthetic concentrations.

In view of these findings it would seem that a major advance in the treatment
of depression would be the development of an oral preparation that activates the
EOS in a similar fashion to analgesic nitrous oxide.

Johannesburg