Considering lab-based findings of the behavioural effects of dopamine agonists, we predicted that dopamine agonist treatment would improve motivational symptoms, but not other depression symptom dimensions; whereas MAO-B inhibitors may improve mood due to their concurrent serotonergic action at higher doses.30 Our secondary hypothesis was that dopaminergic medications with mechanisms of action reliant on pre-synaptic dopamine neuron integrity, such as MAO-B inhibitors, would have attenuated antidepressant effects as pre-synaptic dopaminergic neurodegeneration progressed. The gene discussed is MAOB; the disease is major depressive disorder.