Most clinical major depression responds to standard treatments (medication and psychotherapy); however, a significant subset of depressed patients (15-20%) do not respond to these treatments and are referred to as treatment-resistant major depression (TRMD). New treatments for TRMD are needed, and one promising line of research are drugs known as N-methyl-D-aspartate (NMDA) glutamate receptor antagonists. In a recent pilot study, our group demonstrated that the NMDA antagonist nitrous oxide is effective in TRMD.
All patients will receive 3 randomized, one hour nitrous oxide inhalations to placebo (0% N2O), low dose (25% N2O), and high dose (50% N2O). Inhalation sessions will be at least 4 weeks apart. Mood will be assessed at baseline, 2 and 24 hours, and 1, 2, and 4 weeks post-inhalation for each dose.
