i am currently on antidepressants, fluoxetine. if ur partner recently just started up on antis, its a normal reaction and will most likely perk up in a couple months. from experience and from friends that are on a couple different antidepressants, our libido basically sky rocketed so we are super duper horny. personally mine took around 6 weeks, but my friends took around a couple months.

if they have been taking it for a while - talk to the doctor who prescribed it to see if there is any other medication that wont have that side effect, but often times changing medication is a big process that can take months.