It's possible there was a drug contribution, but mefloquine isn't the only malaria drug, and most people don't take t after reading about the side effects.
I do know, however, two people very closely who suffered severe mental health issues due to mefloquine.
There seems to have been 'something' (anxiety?) definitely going on with Leanne during
the final days/weeks of their journey. Josh said - at the FB page - that Leanne had stated
she was afraid to return to the US. I keep wondering what it was she was afraid of.