 During the single blind phase, the dose of nabilone may be adjusted upward from 1 to 4 mgday based on tolerability at weekly visits.. Any upward dose adjustments will occur in increments of either 1 or 2 mgday if the initial dose is 1 mg or 2 mg per day respectively. If intolerable adverse events occur during any time of the single blind dose adjustment phase, the dose of nabilone may be decreased by 0.5, 1 or 2 mgday if the initial dose is 1 mg, 2 mg or 4 mg per day respectively. A dose of 0.5 mg per day which is not tolerated will lead to study termination. Once a dose reduction has taken place, no further dose adjustments will be permitted. An unscheduled visit between study week 3 and study week 4 will be the last opportunity for dose adjustment. 