I have a scorpio stellium in the 12th house and I have contemplated suicide on many occasions in my life. The worst of it was when I was married to my ex. I would make myself get through the darkest moments , usually a day and I would be fine.
It helps to be on Prozac as well..lol ..there is a strong genetic component to my depression as well.
I would say Saturn aspects especially to the poor moon. Saturn=Depression, fear, fear of change and melancholia and deep sadness. Ironic Saturn is about structure but, when hitting ones moon I believe its too harsh for the moons emotional being with saturn demanding structure.
I have Saturn-Moon, melancholia is my middle name! Always has been. Even at my happiest I'm melancholic and overwhelmed.
I'm very prone to mild depressions, but thats because I'm single and tired of being that. But alas, also very emotionally resillient, and also religious so I do not wish death. Also strong chart ruler, Pluto in scorp.
Yes I agree with that melin. I cringe when I see Saturn-Moon aspects- very repressive. My friend has Saturn conjunct Moon and Saturn square the Sun (ouch) and I see how much she censors her behaviour and emotions to the point of complete suppression. It’s almost impossible for her to let loose and relax and just be herself- Saturn's influence is just so overwhelmingly constrictive. She’s not suicidal (also strong Scorpio) but I can see how that influence could have a really negative impact on someone- especially early in life before Saturn starts showing any pay-off for the hard work thats been done 
Bump
This is an important subject - thanks for bumping it up, Elsa.
Personally I've learned of one person committing suicide during lockdown and of course there have been more reports around this matter and news in the media this year. Isolation normally increases mental health vulnerability.
Reading previous posters' contributions I would agree with water heavy placements, moon saturn aspects (imo more the conjunction, square and opposition) and some neptune aspects behind a higher propensity to consider suicide.
I'm wondering if having them all would really increase vulnerability levels - I think it could.
I laughed reading the idea of scorpios not really REALLY wanting to die. I'm not a scorpio but I have that ascendant and the traditional chart ruler mars in the 8th with the moon and I really REALLY don't want to die (despite the certainty that it will happen.)
Yes, fixed signs...they are true 'stayers' as I describe them.
The natal chart shows potential ('predisposing' factors) and then predictive trends can turn out to be 'precipitating' or vulnerability factors with regards to suicidality.
I'll add for transparency: I did once consider suicide seriously and thought of ways (how) for a few minutes a long time ago. Got help immediately (trusted friends and my therapist at the time) and 9 months after I started to feel like myself again.
Got water placements (wouldn't say heavily water placements -> sun in pisces and the mentioned rising signs), two fixed personal planets, two gemini personal planets (gemini is mentioned in the topic), 4 personal planets in water houses, and neptune harshly aspecting sun and moon.
Personal planets in water houses...perhaps another factor?
For me once was enough and have had worse depressive times since then but the idea hasn't come up. Will check transits and progressions of that time and report back.