What class of antidepressants is considered the oldest?

The correct answer, monoamine-oxidase inhibitors (MAOIs), is recognized as the oldest class of antidepressants. MAOIs were first introduced in the 1950s and were discovered to be effective in treating depression. They function by inhibiting the monoamine oxidase enzyme, which breaks down neurotransmitters such as serotonin, norepinephrine, and dopamine in the brain. This mechanism increases the availability of these neurotransmitters, which are believed to play a key role in mood regulation.

While other classes of antidepressants, such as tricyclic antidepressants (TCAs) and selective serotonin reuptake inhibitors (SSRIs), have since become more common due to their efficacy and safety profiles, MAOIs hold the distinction of being among the first pharmacological treatments developed for depression. Despite their historical significance, the use of MAOIs has declined due to dietary restrictions and potential interactions with other medications, but they remain important in the landscape of psychopharmacology for particular cases, especially treatment-resistant depression.