Suicide is method of gaining massive instant Karma. Karma accrued as a result of suicide is gained in two ways.
Firstly; for terminally defiling the gift of the physical vehicle, which are in short supply in comparison with the huge number of energetic entities requesting incarnate existence.
Secondly; not as a result of the act of suicide, but as a result of the association with the lower frequencies that resulted in the desire to commit the act of suicide.
In essence the first way of gaining suicide-based Karma is a result of the second way.