BACKGROUND: Monoamine oxidase-A (MAO-A) is a treatment target in 
neurodegenerative illness and mood disorders that increases oxidative stress and 
predisposition toward apoptosis. Increased MAO-A levels in prefrontal cortex 
(PFC) and anterior cingulate cortex (ACC) occur in rodent models of depressive 
behavior and human studies of depressed moods. Extreme dysphoria is common in 
borderline personality disorder (BPD), especially when severe, and the molecular 
underpinnings of severe BPD are largely unknown. We hypothesized that MAO-A 
levels in PFC and ACC would be highest in severe BPD and would correlate with 
symptom magnitude.
METHODS: [(11)C] Harmine positron emission tomography measured MAO-A total 
distribution volume (MAO-A VT), an index of MAO-A density, in severe BPD 
subjects (n = 14), moderate BPD subjects (n = 14), subjects with a major 
depressive episode (MDE) only (n = 14), and healthy control subjects (n = 14). 
All subjects were female.
RESULTS: Severe BPD was associated with greater PFC and ACC MAO-A VT compared 
with moderate BPD, MDE, and healthy control subjects (multivariate analysis of 
variance group effect: F6,102 = 5.6, p < .001). In BPD, PFC and ACC MAO-A VT 
were positively correlated with mood symptoms (PFC: r = .52, p = .005; ACC: r = 
.53, p = .004) and suicidality (PFC: r = .40, p = .037; ACC: r = .38, p = .046), 
while hippocampus MAO-A VT was negatively correlated with verbal memory (r = 
-.44, p = .023).
CONCLUSIONS: These results suggest that elevated MAO-A VT is associated with 
multiple indicators of BPD severity, including BPD symptomatology, mood 
symptoms, suicidality, and neurocognitive impairment.