People who become suicidal, do so because they are depressed and are ignorant of any good options. And many of them smoked pot for quite a few years, going through the cycles of paranoia and euphoria thousands of times (cycles that later become mania followed by depression).
They didn’t start smoking pot because of depression or a lack of options. Most of them started smoking pot, because acquaintances told them that it would make them feel great and implied that it would make them more desired as a friend. Many started smoking pot also because they were drunk when pressured to do it. Most who use harder drugs were high on smoke, when the harder drugs were offered.
People who are depressed do not always commit suicide and as far as I know marijuana does not induce the desire to kill ones self.