The tendency to use cannabis is associated with genes linked to
    impulsive behavior, obesity, schizophrenia and bipolar disorder,
    among other traits, according to a study 

The article confuses me because it seems to be presenting cannabis use as purely recreational. Medical use isn't mentioned at all - so we don't know where medical users fit in this study.

Nearly every cannabis user I know is using it for pain, insomnia and/or anxiety.

May Use in the headline would be better written as Regularly Use, to reflect the article.