People with guns in the house are more likely to commit homicide or suicide, according to hundreds of studies in the injury prevention literature. This difference exists even for households that have owned a gun for years, which means that in most cases, the gun was not bought for the purpose of a homicide or suicide that happened years after purchase. The common interpretation of the data is that many people have impulses that might lead them to homicide or suicide, but those who have a gun available can carry out their impulse quickly and easily, so are more likely to do so. By contrast, the suicidal/homicidal impulse does not last long enough for people to actually go and specially buy a gun for the purposes of carrying out their impulse.
Now a study finds that people who attempt suicide by gun are only moderately more likely to attempt again and successfully kill themselves. It may be the case that in many of the gun attempted suicides, the suicidal attempt was just the fulfillment of an impulse facilitated by gun access. If a gun were not available, certainly some people could be determined enough to actually go out and apply for a gun permit and then get a gun, but for many people the impulse would dissipate, and they would not have carried out the impulse.
Other suicide attempt methods associated with only moderate likelihood of a later successful suicide are gassing, jumping from a height, or drowning, and those with low likelihood of successful suicide are cutting and poisoning. Those with high likelihood of successful suicide are hanging, strangulation, or suffocation.
Likely gender is also involved. Cutting and poisoning are more common among women, and women are less likely to be successful at suicide.
The hypothesis about impulse being the cause of gun attempted suicides implies that most of the methods with low or moderate chance of successful later suicide are easily accessible and implemented, and indeed many involve materials easily available and could conceivably be carried out impulsively. The methods with high likelihood of later suicide also involve easily accessible materials, but may involve psychic costs that make them difficult to implement.
In short, I think the Supreme Court may have just increased the suicide and homicide rates by allowing more people easier access to guns that can be available quickly and easily enough to fulfill an impulse that would otherwise dissipate.