"negative effects of nofap"? Seriously?
In case you haven't noticed, four-legged creatures are roaming the planet and up until now haven't complained about not being able to masturbate.
God gifted us humans with these magnificent things called hands. Do you really think masturbation is natural at all?
Real procreation, the kind that produces babies, real human sex, is natural. Masturbation is just a cheap cheat, capable of destroying your soul.
I think the whole purpose of Nofap is to realize just this. There's another way of living that is far more natural, fulfilling, healthy and respectable. If you can't have real sex, you'll need to find other ways to happiness (instead of pleasure). These ways of living will always be more fulfilling. There's so much things you can do that will really make you happy. Masturbation is just temporary pleasure that always leads to frustration. Sex is actually a sacred thing, since life itself depends on it. Wasting semen for the heck of it serves no man. Eventually it only leads to depression and addiction. Once becomes twice, you get the idea... It's hard to control yourself when you first discover something so pleasurable, and you need to have a really strong, almost superhuman will if you plan on moderating this habit.
Please realize that once you had and addiction to pmo, you'll always be very vulnerable to falling back into this habit. The fact you're even asking this should make you think. You know how addictive p, m and o can be. One quickly leads to the other.
If you're tempted to pmo, just think about how people used to live, in the Stone Age, for instance. They didn't have any porn and probably didn't ever waste their strenght on masturbation. They, six-pack warriors, could use all of their strenght escaping whatever beast looking for its next meal. I'm sure they had plenty of real sex, which is why your brain is very easily seduced by this natural reward in the first place. The only problem with porn and masturbation is that in a sense, it's not real. It's an artificial way of simulating real sex, a corruption of this sacred, life-giving thing. In your own mind, when you masturbate, you're probably having sex with someone else, while in reality you're just having sex with yourself. Think about this. It's an escape into fantasy, while in reality you're having sex with the most precious tool on planet Earth: your own hand, which was definitely not designed to have sex with. This self-pleasuring ultimately leads to a shift in your energy, making you introverted, depressed and ashamed.
I'll repeat the question... What negative effects?