As far as I know all studies (certainly most studies) that have found antidepressants as “effective treatments” for depression are much shorter than the durations for which antidepressants are typically prescribed. Most studies last a few months at most. The evidence for long term effectiveness is lacking, however, there is certainly evidence of long term harm.

https://pubmed.ncbi.nlm.nih.gov/21459521/

Unfortunately there is insufficient data on long term outcomes because such studies would be expensive to conduct and the results of such studies would almost certainly be harmful to the extremely lucrative sales of antidepressants.