How Can I Arrest And Reverse Stress, Anxiety And Depression Induced Cognitive Decline?

I have suffered poor mental health for multiple years and noticed a decline in my fluid intelligence. In particular, my verbal proficiency has decreased: I was able to quickly formulate complex, gramatically correct, semantically coherent sentences which referred exactly to the ideas in my mind, using relatively few, well chosen words in the past, when speaking, and I could do so quickly without the use of meaningless place-holding sounds like 'um'. Now, I find that in order to do (not do) any of these things, I must sacrifice (accept) some of the others.

The verbal deficits are simply more salient/noticable/prominent than others, because I can hear myself speak and see what I type. This suggests that the others may be equally severe.

I am not at an age at which these effects are common in the absence of mental health problems.

How can I ( quickly ) slow this decline? If it can be stopped, how can it be stopped? If it can be reversed, how can it be reversed? Are there any drugs I could take which would have this effect? Please assume in your answer that the effects I believe are there are actually there. I believe that my brain is actually shrinking in certain critical areas.

Sorry if this post is inappropriate, I created it for primarily selfish reasons, although it may be helpful (or answers to it may be helpful) to others. I have created this post now because I believe the decline has accelerated sharply in the last months.