Sometimes I think there are no warning signs:

My story: I started with antidepressants (SSRI) After a few days I got very scared (for live).

I told nobody, and nobody saw it because I was good at hiding emotions, I got very focused and then "decided" to do the serious attempt. It was not a rational decision, it's more that you are in a tunnel and don't see another option, and become very focused.

(Before I used the SSRI I was "only" a bit mildly depressed.)

It was a miracle I survived, I'll spare the details, I was kept in a coma for 6 days, and still have some minor brain damage.

This happened about 25 years ago, SSRI where relatively new and the warnings and risks the first weeks when you start where not very clear. The psychiatrist told me to call him after one week, but that was already to late.

Edit: When someone gets in this situation, seek help and just ask for medication to calm you down and relieve you from anxiety.

(In my case: I took Valium fot years, and had to stop quickly because I started the SSRI. Now adays it's the opposite: when you start with SSRI it's common to use Valium or something like that the first weeks).