This experiment is a pilot study involving up to 20 healthy males or females between the ages of 18-65 to test whether a 100-hour ketamine infusion plus clonidine would be more effective, with longer lasting results, then the standard 40-minute ketamine infusion (plus clonidine). Each of the 2 arms, will be evaluated using a between subject, double-blind, randomized design. An additional subset of 20 non-randomized patients, separate from the original randomized clinical trial (RTC), will receive an MRI pre and post ketamine infusion.