Punctuation of this sentence.

[saloom2]

Hello everyone,

Prisons, in addition to increasing access to drugs, soar crime rate, since the concentration of aggressive people on one place may form more friendships. ... etc.

Am I using these punctuation in red correctly?

[Grumpy]

No. Not only that, but the whole construction of the sentence as far as you have gone is also wrong. I'm not sure what you are trying to say, but I'll make a guess, and suggest it be written as follows:

As well as allowing increasing access to drugs, prisons actually contribute to a soaring crime rate, through the friendships formed by aggressive people concentrated in one place.

[saloom2]

Why did you put a comma before through??

[Rover_KE]

Why did you put a comma before 'through'? ?

A single question mark is correct.

In my opinion the comma is optional. Omit it if you wish.

Rover

[saloom2]

Well, is there a reason for making it optional?

[emsr2d2]

Well, is there a reason for making it optional?

The fact that it's optional seems like a pretty good reason.