OK, before I start let me say that I'm posting this in the spirit of honest inquiry. This is not an attack on religion.

But...

People occasionally say, usually after a suicide, that young people don't realise that death is permanent and hence kill themselves, not realising the implications. This lead me to think: are religious beliefs contributing to suicides?

First of all, I realise that most religions say that suicide is wrong, that only god may take away life; but many people ignore, or do not understand this, and (perhaps) simply believe that after death 1) they will continue to exist 2) that they will go to heaven 3) that they will see their dead friends/parents etc. again.

Like I said, I don't intend this as an attack on religion (it would be pretty low) but, rather, I want to see what others think about this.

Are you aware of Emile Durkheim's famous study on suicide that forms the essential beginning of the academic study of sociology?

One of the findings of that study was that religious people were the least likely to commit suicide.  Admittedly, this study was done in the late 19th century and didn't look at religion outside of the US context.

I was not aware of it. I think that we now have a culture of cherrypicking from religion, however, and people may take the afterlife part but reject the suicide is sin bit. I think this is the danger.

I believe that suicide is against Christian doctrine.  Traditionally speaking a suicide was not even allowed to be buried in consecrated Church graveyards.

If this is the case, it should be obvious that suicide, from a Christian perspective, is a ticket to Hell.

Is your question about why there are many religious suicides or a question about why there are not?

Without looking at any facts I'd suggest suicide would be less common among people with emotional supports, and I'd suggest churches can provide those emotional supports. But I'd also suggest a lot of pressure can be built through religion, which I'd think would tend to increase suicide rates. They way I think of it suicide is a social problem, and different churches in the same sect can have very different social dynamics, making it difficult to make meaningful links between beliefs and suicides, or to disprove them.

I think that it varies.  Whether this is sinful or not depends a great deal upon the knowledge and accountability of the individual.  Our Heavenly Father doesn't send people to hell for a mental illness they aren't really in control of.
I'd say that's true of most religions.  When people choose pieces of different religions to believe a la carte it typically isn't the rigorous parts which lead toward real personal growth.

James 4:17 Therefore to him that knoweth to do good, and doeth it not, to him it is sin.

I'm not saying it isn't ordinarily a sin and certainly many have committed it.  What I'm saying is that knowledge is required for an action to be regarded by God as sin.  God knows what they know and whether that knowledge is enough for the person to be justly held responsible for the action.  I would submit that in certain circumstances one who is mentally ill lacks this knowledge.  I won't say how common I think that is because I don't know and I refuse to speculate.