Does Penis Jelqing Cause Natural Penis Enlargement?

hi, i have been reading alot about natural penis enlargement techniques through the means of manual stretching and jeqling. i am looking for an honest answer, and not encouragement to get surgery because i don't need it and can't afford it anyway. i am 21, just under 5 inches in length, and just over 3.5 inches in girth. are the gains people experience from jelqing actually the result of the spongy tissues in the penis expanding, or is it edema, and/or bleeding under the skin? a small number of clinical studies show that penis stretching devices can work, if worn for a length of time. this means that gentle, correct manual stretching must also work. people have seen length gains using this method. if done correctly, does this cause any damage to the penis? does stretching it slowly, over time, lengthen and strengthen the ligaments or, does it make it weaker? are there any possible future negative effects? this is something i want to try to add an inch over time in length to my penis. please can i have all your opinions and advice on this. thank you.