I want to focus on a European perspective, since I am aware that the topic 'suicide' has, eg. in countries like Japan, a vastly different cultural significance.
The question arose for me while watching some semi trashy historic TV show in which one of the 10th century saxon characters stabbes himself to avoid trial for treason. I also remember that in the BBC series Rome suicide was a more common occurrence/topic. I am aware that these drama series are not exactly historic sources, but in my laymen historic education I also remember stumbling over suicide multiple times in real historic sources.
In Christianity suicide is for the most part considered a sin, but it still happened. Is it possible to say if there was a difference in occurrence of suicide between the pre-christian Europe and the christianised one? Was suicide seen as an accepted escape of lifes misery in ancient times? And was it still accepted in Christian lands as an, even if sinfull, still honourable way out?
In our modern times the number of conducted suicides by men massively outweighs that of women. Was there a similar gender difference in other time periods?
How much did the common people know about suicide? Was it a occurrence that happened in most bigger settlements on a regular basis or did it stay a very rare occurrence? Did people even have a general idea how to end their life effectively if they decided to do so?
I remember for example one episode in the German history in which young people copied the suicide of the protagonist in Goethe's 'The Sorrows of the Young Werther'. It seems that they were before either not aware of this 'possibility' or felt morally justified by copying a loved fictional character.
While this question asks generally about the Christian European perspective, I can offer a few insights about how suicide was viewed in a relatively prominent non-Christian society which existed concurrently alongside the Christian peoples throughout most of the medieval period (and which I am familiar with due to my studies) - medieval Lithuania.
It is held in general consensus that medieval Lithuania was a considerably suicide-prone society in comparison to its Christian surroundings. (Gintaras Beresnevičius, Lithuanian historian, expressed this in his study Lithuanian Faith and Mythology/Lietuvių religija ir mitologija, for a prominent example). Mentions of suicides committed by common Lithuanians and Lithuanian nobility alike are among the first mentions of their society we have from the beginning of the 13th century - the Livonian Chronicle of Henry which describes the foundation of the city of Riga and the Order of Brothers of the Sword (the future Livonian Order) has several such mentions: in one instance, according to Henry, "fifty women committed suicide by hanging in Lithuanian villages upon hearing of the deaths of their husbands" in the aftermath of a failed raid in Estonia, and, a Lithuanian duke Dangerutis (Dangeruthe) committed suicide by impaling himself with his own sword after being captured and hearing that his lands in Lithuania were divided among his peers. Such mentions can be found throughout Teutonic sources on the Lithuanian Crusade, depicting events such as Lithuanian soldiers hanging themselves after losing battles, as they could not take the shame of defeat, et cetera. This indicates that the Christians fighting the pagan Lithuanians were witnessing a real phenomenon of common suicide, especially suicide in duress or due to belief that death is preferable to returning defeated.
How much this stance was informed by Lithuanian religion, as opposed to the anti-suicide Christianity, is debatable. Beresnevičius, whom I mentioned before, held that pre-Christian Lithuanian culture formed a fatalistic outlook towards the world, according to which one's death is inevitable and to willingly choose to take one's life sooner rather than later is not particularly a sin, if it done for a cause (a show of defiance against an enemy, or grieving for your loss). There is some anecdotal linguistic evidence towards this outlook in war - the Lithuanian word for "flag, banner" - vėliava, which was historically used for military units in general - originates from the word vėlė ("ghost", "spirit"): this interpretation was particularly enjoyed by Algirdas Julius Greimas, a Lithuanian linguist and researcher of Baltic mythology, who claimed that the semiotic origin of this term came from ancient Lithuanian belief that a unit marches to war alongside all of their ancestral dead, and they themselves become part of the dead. Greimas also developed the theory that Velinas, the Lithuanian god of the underworld, was also the god of war, and so all who participate in war are immediately part of his domain, and so are, in a way, "one foot in the grave" - this is a fringe stance in Lithuanian history as far as I'm aware, but it is known.