A gun only increases the success rate of suicides, it is not a cause.
"Only" increases the success rate, you say.
As it happens, you are simply wrong, Ward.
Because of the higher likelihood of success in killing oneself, the mere presence of the gun increases the number of people who
attempt to kill themselves.
It makes the spontaneous urge far easier to yield to compared to most other methods.
Some pertinent quotes:
"Most attempts are not fatal, and most people who attempt suicide do not go on to die in a future suicide."
One major challenge with studies examining the relationship between gun access and suicide risk has been determining whether people who purchase handguns already have plans in place to harm themselves, or whether the presence of a handgun creates new risks.
The unique, longitudinal nature of the Stanford study helped to disentangle these competing explanations.
"There appears to be some of both happening," said senior author Matthew Miller, professor of health sciences and epidemiology at Northeastern University. "New handgun buyers had extremely high risks of dying by firearm suicide immediately after the purchase. However, more than half of all firearm suicides in this group occurred a year or more later. Consistent with prior work, our findings indicate that gun access poses a substantial and enduring risk."
Ease of acquiring a gun increases suicide rates.
Possession of a gun increases suicde rates.
Both of these things are true.