What type of antidepressant was first used in the 1950s to treat tuberculosis but later showed an elevation in mood?

The correct answer is that monoamine oxidase inhibitors (MAOIs) were initially developed in the 1950s for the treatment of tuberculosis. During clinical trials, it was observed that these medications had a side effect of elevating mood in some patients. This unexpected outcome led to further exploration of MAOIs as antidepressants. The mechanism by which MAOIs work involves inhibiting the monoamine oxidase enzyme, which breaks down neurotransmitters such as serotonin, norepinephrine, and dopamine in the brain. By preventing this breakdown, MAOIs increase the availability of these mood-regulating chemicals, effectively helping to alleviate symptoms of depression.

Tricyclic antidepressants, while effective, were developed later and do not have the same historical background of initial use for tuberculosis. Selective serotonin reuptake inhibitors (SSRIs) emerged even later and are primarily focused on serotonin levels without the initial connection to tuberculosis treatment. Phenothiazines are primarily antipsychotics, not antidepressants, and their use was not centered around the treatment of depression in the way MAOIs were discovered to be effective later on.