NIH study suggests a link between cannabis use and higher levels of suicidal ideation, plan, and attempt.

An analysis of survey data from more than 280,000 young adults ages 18-35 showed that cannabis (marijuana) use was associated with increased risks of thoughts of suicide (suicidal ideation), suicide plan, and suicide attempt. These associations remained regardless of whether someone was also experiencing depression, and the risks were greater for women than for men. 

Read the full article at National Institutes of Health.