In an open-label pilot study conducted as a case series, 12 healthy participants were assessed before, 1 week and 1 month after a 25mg/70kg dose of psilocybin. Participants were assessed on the Depression, Anxiety and Stress Scale, Dispositional Positive Emotion Scale, Positive and Negative Affect Schedule, Profile of Mood States, and State-Trait Anxiety Index. Patients also underwent blood-oxygen level dependent fMRI imaging during the facial recognition task to determine changes in brain function. One week after psilocybin use, negative affect and amygdala responses to facial affect stimuli were reduced, while positive affect and dorsal lateral prefrontal and medial orbitofrontal cortex responses to emotionally-conflicting stimuli were increased. One month following psilocybin use the negative affect and amygdala responses returned to baseline values, while positive affect remained elevated, and a reduction in state-trait anxiety was maintained.