Mechanisms of action of the 5 classes of medications used to treat depression: Selective Serotonin Reuptake Inhibitors (SSRIs); Serotonin/Norepinephrine Reuptake Inhibitors (SNRIs); Tricyclic Antidepressants (TCAs); Monoamine Oxidase Inhibitors (MAOIs); and Atypical Antidepressants