is there a specific combination??

Rahu in the first house irrespective of which Rasi it is , always gives a tendency to commit suicide. Exception, is that only when a benefic is aspect the lagna or associated with Lagna

Rahu in the ascendant does give such tendencies. Ketu in my experience does too.

The difference:=

Rahu in ascendant make a person generally greedy as a overall factor. Such people normally desire a material life, are impatient, and get easily by a life of glamorous proportions. As a corollary to the statement they tend to neglect the spouse, or important interpersonal relations that personally matter..............They have sudden tendencies to suicide like in 'spurts'.

Ketu in ascendant make a person prone to frequent depressions, particullarly due to their oversecretive natures, as a overall factor. Such people generally do not initially desire a material life in particular, are quite patient ( though there is a strong latent impatience in their nature). As a corollary to the statement they neglect themselves and try to focus their life on their spouse or personal interaction............They do not commit sudden siucides, but are often thinking of suicide. They execute planned suicides.

Feedback would be appreciated.

RishiRahul

a weak lagna lord, badly afflicted moon and extremely strong 3rd house (it requires utmost courage to end one's life) may be the additional factors...

A weak lagna lord. badly afflicted moon certainly aids towards it.

Not too sure about the strong 3rd. house. But it could be a factor, if the strong 3rd. house was afflicted by a malefic.

RishiRahul