Who is the one most likely to commit suicide high serotonin level?

The one that most likely to commit suicide is: a 40-year-old with low serotonin activity

Serotonin is the one that control most of positive mood that happen to human (such as sexual desire, sense of appetite, sense of excitement , etc)
People with low serotonin activities tend to rarely or never experience such positive things in their life, which would increase their tendency to commit suicide.