Don't blame his poor mental state on a drug rather it is abundantly clear we have a US president with a florid narcissistic personality disorder (NPD).  He fits all the DSM-V criteria and NPD is known to worsen with age and stress which will explain his increasingly erratic behaviour and unpredictability over time.  I fully expect that he will have to be removed as president when it becomes more apparent he is a real liability for the republic.  

The news media needs to stop beating around the bush and start calling a spade a spade.

https://medium.com/@samvaknin/president-trump-dd064672d9d9#.g91rzz2gf