I understand that access to guns and impulsive behavior can change the suicide rate. What I'm saying is there are other factors that people conveniently ignore and only go after guns.

Here's a source for the switch to natural gas causing the suicide rate to drop by 30 percent:

In England, death by asphyxiation from breathing oven fumes had accounted for roughly half of all suicides up until the 1970s, when Britain began converting ovens from coal gas, which contains lots of carbon monoxide, to natural gas, which has almost none. During that time, suicides plummeted roughly 30 percent — and the numbers haven't changed since.

From your language and the language in this NPR article, the primary blame seems to be on coal gas. If only we could make it harder for people to kill themselves, we could significantly lower the suicide rate.

Investigating the suicide rates of the 27 countries with data on sales of all antidepressants between 1980 and 2000, Ludwig and Morcotte (2005) have reported that after controlling for some relevant sociodemographic factors (unemployment, GDP, gender, divorce rate) only the increase of antidepressant (mostly SSRI) utilization correlated significantly with declining national suicide rates.

Increased antidepressant usage lowers the suicide rate. Let's look at antidepressant usage in the UK from the 70's forward.

Substantial increases in antidepressant prescribing have been observed in the United Kingdom over the past two decades. Data from the Prescription Pricing Authority show that antidepressant prescribing in England increased by 36% to 7.3 million items per quarter between 2000 and 2005, and costs increased by 20% to £91 million (€100 million; $145 million) per quarter.1 Prescribing of selective serotonin reuptake inhibitors increased by 45% during this period and accounted for half of all prescriptions and costs for antidepressant drugs. Further rises, predominantly in the prescription of selective serotonin reuptake inhibitors, have occurred since these data were released, although costs have fallen since 2005 because several key patents have expired.2 In addition, evidence exists for rises in antidepressant prescribing since the middle of the 1970s