The purpose of this study is to look at the effect of using Mirtazapine to target a specific pathway in the body, that relies on a natural chemical the body produces called 'serotonin', in patients with spinal cord injury (SCI) and non-injured persons during sleep. During this part of the study participants will be asked to take Mirtazapine (15mg per day) and a placebo in a random fashion, each for a one week period (drug period) of time followed by one week without drugs (washout period). The drugs will not be taken all at the same time, but each will be taken separately for one weeks followed by a night study to look at the effect the Mirtazapine/placebo pill has on the way the body responds during sleep.

Randomized placebo controlled cross-over study. Each subject will be studied on two separate occasions: (1) Mirtazapine vs. placebo for one week; the participants will be blinded to whether they are taking Mirtazapine or placebo. After the one week treatment a sleep study will be repeated. Mirtazapine will be given at 15 mg dose before bed-time. (2) Cross over medication for one week will be followed by a second sleep study.

Inclusion Criteria:

• Adults with SCI (>6months after spinal cord injury) at the T6 level/above
• Non-injured adults

Exclusion Criteria:

• Pregnant and lactating females
• Heart failure, vascular disease, or stroke
• Advanced chronic obstructive pulmonary disease (COPD), liver disease, and chronic kidney disease
• BMI >38 kg/m2
• Mechanical ventilation dependence

Adverse event data were collected during the one-week interventions during which the participants were taking Mirtazapine or placebo

Of the 15 participants who started the study protocol, 13 received Mirtazapine and 12 received a placebo due to participant withdrawal and physician removal.

• The sample size is small and the majority are males, therefore findings from this study may not be applicable to the general population
• The study required heavy instrumentation which may have affected natural sleep