There are certainly certain mental illnesses that require medication. For example, schizophrenia.
And some patients with anxiety disorders and/or depression will benefit from medication. But other patients will do just as well or better with (only) CBT or other psychotherapy, without having to endure the side effects of medication. And the benefits of psychotherapy may be more enduring than the benefits of medication.
There have been a bunch of studies that address this issue. Here’s one, just as an example:
https://www.ncbi.nlm.nih.gov/pmc/articles/pmc2748674/Post Edited By Moderator (getting by) : 10/20/2019 1:48:42 PM (GMT-6)