That isnt to say there are not problems with this kind of technology that needs addressing, but I would rank this pretty low in a list of scary technology.
"With grate abuse potential comes grate responsibility to make sure it's not abused." category.
An let's be honest if I would be really deeply stuck in serve depression and the only way way out is to (in a dystopian future) give partial control over my mental state and as such live to a coperation, I probably still would do it. Because being able to live a live which is only partially my live is still better then just being alive instead of living.
What makes this modification much worse than a pacemaker? I can see why it would be bad to be dependent on an internal artificial device, but not why it would be worse than a heart device.
2. it's in a more space constraint place, scare tissue can force you to place "later" implants at different places, but as there is not much space there might not be alternative paces.
3. pacemaker are a "relative" simple well understood implant, you _could_ build pretty dump/"un-hackable" ones
4. theoretically what can be used to relive depression can also be used to manipulate you, like activate it less then possible normally except if you are in a shopping mall.. (well setting aside that wireless communication with a implant while possible isn't always simple). A pacemaker can "only" kill you, which always leavs the question why it didn't work even if there is no prove that it did kill you.
Also modern pacemakers are scary, too. I mean seriously you can assassinate people by hacking their pacemaker without touching them...
It's basically making you dependent on a drug but you have to commit to a specific producer upfront and changing it later on is a huge cost and risk undertaking and maybe even impossible (due to scare tissue).
This basically makes you fully dependent on the company producing the implant.
Now some would say it's like a peace maker, but from what I can tell with my limited understanding of biology it's much worse (and peace makers are more scary than many people realize as today a "no contact" hacking of peacemakers is possible as far as I know)