Question

Hello,
Some time ago, after I tried treatment for attention disorders using a stimulant, I felt that my perspective on reality had changed. Even some time after stopping the treatment. (In retrospect, it became clear that the treatment was bad for me, and that it left effects for a period afterward.)
I thought that I was simply much more intelligent (following the treatment), and that maybe this is how exceptionally intelligent people approach the world. (A painful approach, it should be noted.)
I looked at the world in fully causal terms. I looked at human beings, including wicked people (throughout history), as people who, through a causal chain not dependent on them, became that way. (And I didn’t understand how, in religion, we so strongly label them as wicked.)
I wanted and tried to believe in free will, and I defined myself that way, but inside I had doubts. It was a kind of delusion, characterized by “normality” and “logical” arguments, but the conclusion was fairly decisive. (And again, it caused me to be a slave to everyday causality.)
You’re not a psychologist, I know, but it was important to me to mention the above in order to ask the question that the title gives away. (It should be noted that this phenomenon passed.)
I read a study claiming that the inability to believe in free will stems from, or can stem from, a mental problem. I remembered that during that “bad” period, I watched a video (if I’m not mistaken) on YouTube (if I’m not mistaken), in which you claimed that there are people who said that they do not feel that they have free choice.
The question is whether, over the years in which you’ve dealt with this field, you have become aware of a connection between a mental problem and disbelief in free will?
And if we are to a great extent built upon influences on our psyche, is there still room for philosophy in our world? (Every philosophical idea stems from subjective principles, including nihilism—which cannot be proven true.)
 
Thank you for the platform!