It's not nihilism "per se", it is its misinterpretation that does, as it just teaches you that nothing has meaning, but nothing can stop you to enjoy life regardless, if you care enough.
What's more interesting is that nihilism actually could help people who are trappled in an endless useless circlejerk about religion and feelings of incoming punishment living a freer and more mentally stable life.
I wholeheartedly agree
I coincidentally found a post I made somewhere else that I think addresses this very issue (although, ironically, it was in a thread that ended up being more related to why people are so -against- suicide):
"I'm pretty sure it's a whole lot more than religion perpetuating the problem here. Most atheists seem to think life is just as valuable as religious people, and are just as disturbed by pain, suffering, and DEATH. The real problem, I think, is the human condition. The desire to survive is very powerfully ingrained in us. Even among us, many have talked about just how hard it really is to kill yourself, no matter how badly you want to die. This is our survival instinct kicking in trying to keep us alive.
If suicide were readily embraced and encouraged by society, it would pose a very real threat to the perpetuation of our species (not that it matters 'cause we really are all gonna die anyway because of global warming in like 1,000 years or something... or so I've been told.) I'm not trying to defend pro-lifers, I'm just trying to say that this may all be part of nature's defense mechanism.
Also, I believe that in the minds of pro-lifers, the concept of embracing suicide for other people is subconsciously a threat to their very way of thinking, and their way of life; it's just completely unthinkable for them, like shooting one of their kids or something like that. It's all psychological or biological."
One thing I tried to imply here, but didn't directly state, is that one of our basic psychological needs as human beings is the need to feel like our life has some kind of purpose or meaning, or that we are significant in some way. Without this, we simply can't cope with our existence as purposeless, meaningless creatures.
Obviously I speak from personal experience. My brother as well, being a nihilist, while not being actively suicidal, is far from living a happy life. He's very disturbed as well, and has talked about killing himself someday after our parents are dead many times (it's hard to figure him out, because he likes playing with people's minds, and frequently says things that contradict statements he's made in the past). He's also absurdly intelligent, which is probably part of how he is able to keep on living such a stable life in spite of his psychological difficulties.
Furthermore, obviously many of the people here who ARE suicidal seem to think that their lives are meaningless, and that life in and of itself is meaningless. Whether that is because they are suicidal, or if they are suicidal because of it, or it is just coincidental is unknown. I think this is a good question to ask, actually; how many of you out there feel like the realization that life is meaningless contributed to your negative mental state? Also, if you don't mind my asking, I'm curious to know why you, Fylobatica, are suicidal as well.